中川 誠司

Some normal-hearing listeners report difficulties in speech perception in noisy environments, and the cause is not well understood. The present study explores the correlation between speech-in-noise reception performance and cochlear mechanical characteristics, which were evaluated using a principal component analysis of the otoacoustic emission (OAE) spectra. A principal component, specifically a characteristic dip at around 2-2.5 kHz in OAE spectra, correlated with speech reception thresholds in noise but not in quiet. The results suggest that subclinical cochlear dysfunction specifically contributes to difficulties in speech perception in noisy environments, which is possibly a new form of "hidden hearing deficits."

In bone conduction, vibrators are usually pressed onto the mastoid process, however, bone-conducted ultrasound (BCU) presented to body parts distant from the head can also be perceived. To elucidate mechanisms of the distantly presented BCU perception, transmissions of BCU were investigated on living human bodies. First, vibration at the external auditory meatus were measured when 30 kHz BCU was presented to distal parts. Second, vibrations of the upper limb were measured at nine surface points lined up straight from the forearm to shoulder when 30 kHz BCU was presented to nearby the wrist. The results showed that prominent spectrum peaks corresponding to the stimulus-frequency were observed at all parts. The vibration tended to decrease depending on the distance between the stimulus and measurement points, however, some exceptions existed. Efficiency of the BCU transmission seems to vary depending on factors like shape of the body, acoustical properties of the tissue, and coupling of the vibrator and the skin. (C) 2019 The Japan Society of Applied Physics

Bone-conducted ultrasound (BCU) is perceived even by the profoundly hearing impaired and a novel hearing aid has been developed. In the BCU hearing aid, the ultrasonic carrier is amplitude-modulated by speech signals and presented to the mastoid process of the temporal bone by a vibrator. However, BCU presented to parts of the body distant from the head can be perceived. In this study, vibration at the external auditory meatus was measured when amplitude-modulated BCU was presented to distal parts of the body. The results showed spectrum peaks corresponding to the carrier frequency (30 kHz) and the modulation frequency. The peak level of the carrier frequency tended to decrease depending on the distance between the external auditory meatus and the stimulation part basically. On the other hand, the peak level of the modulation frequency did not change with the distance between the external auditory meatus and the stimulation part, whereas the effect of modulation frequency was significant. (C) 2019 The Japan Society of Applied Physics

We introduce a new approach for locating earthquakes using arrival times derived from waveforms. The most costly computational step of the algorithm scales as the number of stations in the active seismographic network. In this approach, a variation on existing grid search methods, a series of full waveform simulations are conducted for all receiver locations, with sources positioned successively at each station. The traveltime field over the region of interest is calculated by applying a phase picking algorithm to the numerical wavefields produced from each simulation. An event is located by subtracting the stored traveltime field from the arrival time at each station. This provides a shifted and time-reversed traveltime field for each station. The shifted and time-reversed fields all approach the origin time of the event at the source location. The mean or median value at the source location thus approximates the event origin time. Measures of dispersion about this mean or median time at each grid point, such as the sample standard error and the average deviation, are minimized at the correct source position. Uncertainty in the event position is provided by the contours of standard error defined over the grid. An application of this technique to a synthetic data set indicates that the approach provides stable locations even when the traveltimes are contaminated by additive random noise containing a significant number of outliers and velocity model errors. It is found that the waveform-based method out-performs one based upon the eikonal equation for a velocity model with rapid spatial variations in properties due to layering. A comparison with conventional location algorithms in both a laboratory and field setting demonstrates that the technique performs at least as well as existing techniques.

Bone-conducted ultrasound (BCU) can be heard for both normal-hearing and some profoundly deaf individuals. Moreover, amplitude-modulated BCU can transmit the speech signal. These characteristics of BCU provide the possibility of the developing a bone-conducted ultrasonic hearing aid. Previous studies on the perception mechanism of speech-modulated BCU have pointed to the importance of temporal rather than frequency information. In order to elucidate the perception of speech-modulated BCU, further investigation is need concerning the processing of temporal information. The temporal processing of air-conducted audible sounds (ACASs) involves the integration of closely presented sounds into a single information unit. The long-temporal window of integration was estimated approximately 150-200 ms, which contribute to the discrimination of speech sound. The present study investigated the long-temporal integration system for BCU evaluated by stimulus omission using magnetoencephalography.Eight participants with normal hearing took part in this study. Ultrasonic tone burst with the duration of 50 ms and frequency of 30 kHz was used as the standard stimulus and presented with steady onset-to-onset times or stimulus-onset asynchronies (SOAs). In each sequence, the duration of the SOAs were set to 100, 125, 150, 175, 200, or 350 ms. For deviant, tones were randomly omitted from the stimulus train. Definite mismatch fields were elicited by sound omission in the stimulus train with an SOA of 100-150 ms, but weren't with an SOA of 200 and 350 ms for all participants.We found that stimulus train for BCUs can be integrated within a temporal window of integration with an SOA of 100-150 ms, but are regarded as a separate event when the SOA is 200 or 350 ms in duration. Therefore, we demonstrated that the long-temporal window of integration for BCUs estimated by omission was 150-200 ms, which was similar to that for ACAS (Yabe et al. NeuroReport 8 (1997) 1971-1974 and Psychophysiology. 35 (1998) 615-619). These findings contribute to the elucidation and improvement of the perception of speech-modulated BCU.

A brain-computer interface (BCI) translates brain signals into commands for the control of devices and for communication. BCIs enable persons with disabilities to communicate externally. Positive and negative affective sounds have been introduced to P300-based BCIs; however, how the degree of valence (e.g., very positive or positive) influences the BCI has not been investigated. To further examine the influence of affective sounds in P300-based BCIs, we applied sounds with five degrees of valence to the P300-based BCI. The sound valence ranged from very negative to very positive, as determined by Scheffe's method. The effect of sound valence on the BCI was evaluated by waveform analyses, followed by the evaluation of offline stimulus-wise classification accuracy. As a result, the late component of P300 showed significantly higher point-biserial correlation coefficients in response to very positive and very negative sounds than in response to the other sounds. The offline stimulus-wise classification accuracy was estimated from a region-of-interest. The analysis showed that the very negative sound achieved the highest accuracy and the very positive sound achieved the second highest accuracy, suggesting that the very positive sound and the very negative sound may be required to improve the accuracy.

The auditory P300-based BCI was improved by changing stimuli. However, the current method needed time for recording training data. The time can be saved by the subject-to-subject transfer learning. However, the suitable classifier for the learning remains unknown. As a first step, this study compared the classifiers for the transfer learning of the BCI. They were evaluated on the dataset of a five-class affective auditory P300-based BCI. EEG data from sixteen subjects were assigned for the training, then data from the other six subjects were used for the testing. Classifiers such as the linear support-vector machine (SVM lin.), the kernel SVM (SVM RBF), the quadratic discriminant analysis were applied and compared. As a result, the SVM lin. and the SVM RBF were suitable for this problem. The best mean classification accuracy was achieved by the SVM lin. (68.7%), and a subject showed 86% accuracy at best. These results suggest that some subjects can operate the BCI without recording his/her training data.

To extract an effective feature in prediction of subjective impressions from single-trial neurophysiological recordings, the spatial filter that extracts brain activities related to impressions were constructed using the common spatial pattern (CSP). We focus on subjective preference induced by chords composed of 3 notes with different frequency ratio. Magnetic cortical activities while hearing chords and comparative judgment on pair of them were measured. The predictive model that predicts the scale value of preference was trained using the CSP-based feature for each participant. The result of the evaluation experiment shows that the CSP-based feature improved the mean prediction accuracy in all participants, compared with the other features without spatially filtering. Furthermore, the capability of construction of a spatial filter that extracts cortical activities varying with degree of preference using the comparative judgments was indicated.

Bone-conducted ultrasound (BCU) can be heard clearly and can transmit speech information using amplitude-modulation (AM). Additionally, BCU is perceived even when presented to body parts distant from the head, like the neck, trunk, and arm. It is expected that demodulated low-frequency components appear as a result of the nonlinearity existing in the human body when amplitude-modulated BCU (AM-BCU) is presented to such distal locations. First, to elucidate demodulation characteristics in the propagation process of such distantly-presented BCU, vibration at the external auditory meatus was measured when AM-BCU was presented to the neck, shoulder, upper limb, breastbone and backbone. The results showed spectrum peaks corresponding to the carrier frequency (30 kHz) and the modulation frequency. The level of the peak of the carrier tended to decrease depending on the distance between stimulation and measurement points, however, the peak of the modulator did not change with distance. Second, vibrations around the cartilage of the auricle, tragus and articulations, which have strong nonlinearity, were measured. The demodulation components were larger for the auricle and tragus than for the peripheral articulations. These results suggest that demodulation mainly occurs in the vicinity of the ear even when BCU is presented to distal body parts.

In bone-conduction, a transducer needs to be clamped strongly against the mastoid process of the temporal bone and this has caused severe pain and discomfort to the users. To solve such defects of bone-conduction, "cartilage-conduction" has been proposed and applied to several devices such as hearing aids and smartphones. In this study, psychophysical measurements and brain magnetic field measurements were conducted to objectively evaluate the frequency resolution characteristics of the cartilage-conduction hearing. The results indicate that in a certain range of frequencies, the cartilage-conduction hearing has nearly equal frequency resolution to that of conventional bone-conduction and air-conduction hearing.

High-frequency sound above 20 kHz can be heard clearly via bone conduction (Bone-conducted ultrasound: BCU). Additionally, BCU is perceived even when presented to body parts distant from the head, like the neck, trunk, and arms, and is expected to be applied for novel devices that transmit sound selectively to persons who touched by a vibrator on the arm or other parts of the body. First, hearing thresholds were measured when 30-kHz tone-burst was presented to the neck, trunk and arms in normal hearing participants. The results showed that BCU presented to the distal parts, including the lower arm, can be perceived at least in normal hearing participants, but threshold increased depending on the distance from the head. Second, the vibration of the ear canal was measured using an acceleration sensor when a 30-kHz tone was presented to the neck, arms, and trunk. A prominent spectrum peak corresponding to the stimulus frequency was obtained. Further, the vibration tended to attenuate when the stimulus points were moved away from the head, although some exceptions existed. Third, the vibration of the upper limb was measured at 9 surface points lined up from the forearm to shoulder when BCU was presented near the wrist. The vibration basically tended to attenuate depending on the distance from the vibrator; however, some points at raised upper-arm muscle showed larger amplitudes. These results suggest that efficiency of the propagation varies depending on the stimulus points, and the upper-arm muscle are suitable also on a stimulus location of BCU.

Bone-conduction has been used as a hearing aids for people with conductive hearing impairment, but there was a problem in the wearability of the vibrator. To solve the problem, cartilage-conduction (CC) that transmits the vibrator to the auricular cartilage has been proposed and applied to hearing aids and smartphones. The characteristics of CC perception vary depending on a number of variables, including the placement of the vibrator within the pinna, the contact area of the vibrator and the contact pressure, but the effects of such conditions have not been studied. In this study, we observed variations of detection threshold and ear canal sound pressure (ECSP) depending on the position of the vibrator within the auricle. Tone bursts with frequencies from 250 to 8,000 Hz were transmitted to the upper, middle and lower parts of the auricle. Both experiments were conducted under conditions in which the vibrator did not come into contact with the auricle. The results showed that the threshold decreased and the ECSP increased when transmitted to the middle and lower auricles at lower frequencies (250 and 500 Hz). These results provide useful information not only to optimize the devices using CC, but also to elucidate the peripheral mechanism of CC perception.

Bone conduction (BC) is another way of sound transmission for our hearing perception besides of air conduction. It conducts sound through skin and skull, bypassing part of the ear canal. The position where the vibrator is put on one's head makes a difference in BC transmission. Although standards of bone conduction were established on the position of the mastoid (the prominence of the skull behind the ear), nowadays manufacturers favor bone-conducted headphone whose vibrator is put on the position of the condyle (the articular process of the ramus of the mandible bone, in front of the ear). However, there are not enough data in details for the condyle. In this research, hearing thresholds and ear-canal sound pressure on the condyle and the mastoid were measured, and a comparison between them was made to investigate the difference of BC transmission between the two positions, followed by a discussion on the influence of placement on bone conduction.

Our previous study reported that a preceding sound, regardless of whether it induced a medial olivocochlear bundle reflex (MOCR) by itself, expedites MOCR, and a 60-dB-SPL preceding-noise, which also induces an MOCR, that enhances, in addition to expediting, the MOCR. The current study compares the dependency of the enhancing and expediting effects on the preceding time interval. The MOCR is induced by sounds and exerts an inhibitory effect on the outer hair cells. The suppressive effect was assessed non-invasively in terms of the suppression of otoacoustic emissions (OAEs) induced by a contralateral acoustic stimulation, referred to as MOCR elicitor. A 60-dB-SPL noise was used as a preceding sound, and the inter-stimulus interval (ISI) between the preceding sound and the MOCR elicitor was varied from 0.5 to 2 s. The MOCR strength decreased as the ISI became larger and reached the same level as without a preceding sound within 2 s of ISI. In contrast, the onset delay of the MOCR did not depend on the ISI and was still significantly smaller than without a preceding sound even at 2 s of ISI. The difference in the dependency of the preceding time interval implicates that the preceding-sound-induced enhancing and expediting effects are underpinned by different mechanisms. Effects of a preceding sound on medial olivocohlear bundle reflex as a function of the preceding time interval.

There is a projection of efferent nerve fibers called the olivocochlear bundle connecting the brainstem to the outer hair cells (OHCs). It is said that the olivocochlear system protects the inner ear by responding to sounds and suppressing the OHC amplification. Therefore, measuring the reaction (medial olivocochlear reflex; MOCR) strength is expected to be an applicable method of evaluating the possibility of noise-induced hearing impairment in advance. Since the MOCR strength fluctuates with each measurement, there is a problem that it is difficult to evaluate the function of the MOC system stably. In this study, we examined the influence of fluctuation of awareness during sleeping on MOCR. The awareness was evaluated objectively using electroencephalogram, and MOCR strength was evaluated by measuring otoacoustic emissions, which reflect the OHC amplification. There was a significant positive correlation between MOCR strength and a wave amplitudes, which reflects awareness. This result indicates that MOCR strength, and hence the inner ear protective function become weaker as awareness decreases. Therefore, exposure to loud sounds during a decline in awareness may increase the risk of causing noise-induced hearing impairment.

For high reliability non-volatile memory cell dielectrics, hydrogen-free deuterated charge-trap SiN and tunnel SiON films are demonstrated. By using deuterated ammonia instead of ammonia as nitridation species in ALD cycles, an ultra-high deuterium/hydrogen ratio has been successfully obtained in both films, and these films showed good endurance for program / erase stress and data retention properties in MONOS capacitors.

The current study investigated the effect of a preceding sound on the medial olivocochlear reflex (MOCR), which is a sound-activated feedback response that controls the input to the auditory system. We used 60- and 40-dB noise and a 40-dB tone burst as preceding sounds, and evaluated their effects on the time course and strength of the MOCR. The MOCR was assessed non-invasively in terms of the suppression of otoacoustic emissions induced by contralateral acoustic stimulation. We found that (1) all the preceding sounds we used, regardless of whether they induced an MOCR by themselves, expedited the MOCR by up to 90 ms, and (2) a 60-dB-preceding-noise, which itself induces an MOCR, not only expedites but also enhances the MOCR. (c) 2018 The Author(s).

Recently, brain computer interface (BCI) technologies that control external devices with human brain signals have been developed. However, most of the BCI systems, such as P300-speller, can only discriminate among options that have been given in advance. Therefore, the ability to decode the state of a person's perception and recognition, as well as that person's fundamental intention and emotions, from cortical activity is needed to develop a more general-use BCI system. In this study, two experiments were conducted. First, articulations were measured for Japanese monosyllabic utterances masked by several levels of noise. Second, auditory brain magnetic fields evoked by the monosyllable stimuli used in the first experiment were recorded, and neuronal current sources were localized in regions associated with speech perception and recognition - the auditory cortex (BA41), the Wernicke's area (posterior part of BA22), Broca's area (BA22), motor (BA4), and premotor (BA6) areas. Although the source intensity did not systematically change with SNR, the peak latency changed along SNR in the posterior superior temporal gyrus in the right hemisphere. The results suggest that the information associated with articulation is processed in this area.

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf and a novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid) has been developed. In the BCU hearing aid, the vibrator is pressed onto a part of the cranial bone behind the ear (mastoid process). However, BCU can be heard on distal parts of the body; i. e., the muscle of the neck, the clavicle, and the upper limb. In this study, to assess basic properties of such distal-presented BCU hearing, hearing thresholds were measured when 30-kHz tone bursts were presented to the neck and the upper and lower arms in normal hearing participants. Further, to assess the basic capability of transferring information by the distal-presented BCU hearing, temporal modulation transfer functions (TMTFs), that reflect the temporal resolution of the hearing, were estimated for 30-kHz carrier. The results showed that BCUs presented to the distal parts, including the lower arm, can be perceived at least in the normal hearing, whereas threshold increased depending on the distance from the head. Also, the temporal resolutions of the distal-presented BCU hearing at the neck, and the upper and lower arms were comparable to that of the mastoid process of the temporal bone. These results provide useful information not only for the improvement of the existing BCU hearing aid, but also for the development of novel distal-presented BCU devices that can provide sound information selectively to the specific person who touches the device by the arms or so.

Bone-conducted ultrasound (BCU) is even perceived by the profoundly sensorineural deaf; however, the mechanisms involved remain unclear. Acoustic fields in the external auditory meatus and vibrations of the tympanic membrane (TM) under BCU stimulation were measured to examine the generation of audible subharmonics in the bone-conduction transmission pathway. In the results, no significant audible-frequency signals were observed. These findings indicate that nonlinear distortions do not contribute to BCU perception and specific properties of BCU perception may be related to mechanisms in the cochlea or afferent neural pathway.

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural hearing-impaired and has been applied to a novel hearing aid. The vibrator is usually pressed against a part of the cranial bone behind the ear (mastoid process); however, BCU presented to parts of the body distant from the head can be perceived. In this study, to assess the basic properties of distantly presented BCU hearing, hearing thresholds were measured when 30 kHz tone bursts were presented to the neck and the upper and lower arms in normal-hearing participants. Furthermore, temporal modulation transfer functions (TMTFs), which reflect the temporal resolution of hearing, were estimated for the distantly presented 30 kHz carrier. The results showed that BCU presented to parts of the body distant from the head, including the lower arm, can be perceived at least by normal-hearing persons, whereas the threshold increased depending on the distance from the head. Moreover, the temporal resolutions of the hearing of BCU distantly presented to the neck and the upper and lower arms were comparable to that distantly presented to the mastoid process of the temporal bone. (C) 2018 The Japan Society of Applied Physics

For better understanding of frequency dependence (dispersion) of seismic wave velocities caused by stress-induced fluid flow, broadband laboratory measurements were performed on a suite of synthetic glass media containing both equant pores and thermal cracks. Complementary forced oscillation, resonant bar, and ultrasonic techniques provided access to millihertz-hertz frequencies, similar to 1kHz frequency, and similar to 1MHz frequency, respectively. The wave speeds or effective elastic moduli and associated dissipation were measured on samples under dry, argon- or nitrogen-saturated, and water-saturated conditions in sequence. The elastic moduli, in situ permeability, and crack porosity inferred from in situ X-ray computed tomography all attest to strong pressure-induced crack closure for differential (confining-minus-pore) pressures <30MPa, consistent with zero-pressure crack aspect ratios <4x10(-4). The low permeabilities of these materials allow access to undrained conditions, even at subhertz frequencies. The ultrasonically measured elastic moduli reveal consistently higher shear and bulk moduli upon fluid saturationdiagnostic of the saturated-isolated regime. For a glass rod specimen, containing cracks but no pores, saturated-isolated conditions apparently persist to subhertz frequenciesrequiring in situ aspect ratios (minimum/maximum dimension) <10(-5). In marked contrast, the shear modulus measured at subhertz frequencies on a cracked glass bead specimen of 5% porosity, is insensitive to fluid saturation, consistent with the Biot-Gassmann model for the saturated-isobaric regime. The measured dispersion of the shear modulus approaches 10% over the millihertz-megahertz frequency range for the cracked and fluid-saturated mediaimplying that laboratory ultrasonic data should be used with care in the interpretation of field data.

Mid-infrared properties are reported of the west hot spot of the radio galaxy Pictor A with the Wide-field Infrared Survey Explorer (WISE). The mid-infrared counterpart to the hot spot, WISE J051926.26-454554.1, is listed in the AllWISE source catalog. The source was detected in all four of the WISE photometric bands. A comparison between the WISE and radio images reinforces the physical association of the WISE source to the hot spot. The WISE flux density of the source was carefully evaluated. A close investigation of the multi-wavelength synchrotron spectral energy distribution from the object reveals a mid-infrared excess at the wavelength of λ = μm with a statistical significance of over the simple power-law extrapolation from the synchrotron radio spectrum. The excess is reinforced by single and double cutoff power-law modeling of the radio-to-optical spectral energy distribution. The synchrotron cutoff frequency of the main and excess components was evaluated as 7.1 × 1044 Hz and 5.5 × 1013 Hz, respectively. From the cutoff frequency, the magnetic field of the emission region was constrained as a function of the region size. In order to interpret the excess component, an electron population different from the main one dominating the observed radio spectrum is necessary. The excess emission is proposed to originate in a substructure within the hot spot, in which the magnetic field is a factor of a few stronger than that in the minimum-energy condition. The relation of the mid-infrared excess to the X-ray emission is briefly discussed.

This paper presents coupled hydro-mechanical modeling of hydraulic fracturing processes in complex fractured media using a discrete fracture network (DFN) approach. The individual physical processes in the fracture propagation are represented by separate program modules: the TOUGH2 code for multiphase flow and mass transport based on the finite volume approach; and the rigid-body-spring network (RBSN) model for mechanical and fracture-damage behavior, which are coupled with each other. Fractures are modeled as discrete features, of which the hydrological properties are evaluated from the fracture deformation and aperture change. The verification of the TOUGH RBSN code is performed against a 2D analytical model for single hydraulic fracture propagation. Subsequently, modeling capabilities for hydraulic fracturing are demonstrated through simulations of laboratory experiments conducted on rock-analogue (soda-lime glass) samples containing a designed network of pre-existing fractures. Sensitivity analyses are also conducted by changing the modeling parameters, such as viscosity of injected fluid, strength of pre-existing fractures, and confining stress conditions. The hydraulic fracturing characteristics attributed to the modeling parameters are investigated through comparisons of the simulation results.

We conducted laboratory studies on the geophysical signals from Arctic saline permafrost soils to help understand the physical and mechanical processes during freeze-thaw cycles. Our results revealed low electrical resistivity (<20 Omega m) and elastic moduli (7.7 GPa for Young's modulus and 2.9 GPa for shear modulus) at temperatures down to similar to-10 degrees C, indicating the presence of a significant amount of unfrozen saline water under the current field conditions. The spectral induced polarization signal showed a systematic shift during the freezing process, affected by concurrent changes of temperature, salinity, and ice formation. An anomalous induced polarization response was first observed during the transient period of supercooling and the onset of ice nucleation. Seismic measurements showed a characteristic maximal attenuation at the temperatures immediately below the freezing point, followed by a decrease with decreasing temperature. The calculated elastic moduli showed a non-hysteric response during the freeze - thaw cycle, which was different from the concurrently measured electrical resistivity response where a differential resistivity signal is observed depending on whether the soil is experiencing freezing or thawing. The differential electrical resistivity signal presents challenges for unfrozen water content estimation based on Archie's law. Using an improved formulation of Archie's law with a variable cementation exponent, the unfrozen water content estimation showed a large variation depending on the choice of the resistivity data during either a freezing or thawing cycle. Combining the electrical and seismic results, we suggest that, rather than a large hysteresis in the actual unfrozen water content, the shift of the resistivity response may reflect the changes of the distribution pattern of the unfrozen water (or ice) in the soil matrix during repeated freeze and thaw processes. Collectively, our results provide an improved petrophysical understanding of the physical and mechanical properties of saline permafrost during freeze - thaw transitions, and suggest that large uncertainty may exist when estimating the unfrozen water content using electrical resistivity data. Published by Elsevier B.V.

This study was performed to determine significant light wavelengths to improve color discrimination ability of subjects with deutan. We conducted both the Ishihara test and the Farnsworth Panel D-15 test for subjects with deutan and normal color vision. Seven different LED lights from 450 to 660 nm and an additional D65 white lamp were utilized to change the lighting conditions, including the wavelength and intensity. The results of the Ishihara test and D-15 test showed that color identification of deutans was markedly improved with the longer wavelength LEDs regardless of the intensity of the additional D65 lamp. Notably, the error rates of deutans in the Ishihara test were < 25% for LED wavelengths of 630 and 660nm. In the case of subjects with normal color vision, the D65 lamp abolished the errors in the Ishihara test, regardless of the LED wavelength. Addition of the D65 lamp also decreased the number of crossings in the D-15 test. These results suggested that illumination by LED light with longer wavelengths, such as 630 and 660nm, may provide deutans with greater red-green discrimination ability in both the Ishihara test and the Farnsworth Panel D-15 test. (C) 2016 Wiley Periodicals, Inc.

Noise induced by a heating, ventilation and air conditioning (HVAC) system in a vehicle is an important factor that affects the comfort of the interior of a car cabin. Much effort has been devoted to reduce noise levels, however, there is a need for a new sound design that addresses the noise problem from a different point of view. In this study, focusing on the auditory impression of automotive HVAC noise concerning coolness and warmness, psychoacoustical listening tests were performed using a paired comparison technique under various conditions of room temperature. Five stimuli were synthesized by stretching the spectral envelopes of recorded automotive HVAC noise to assess the effect of the spectral centroid, and were presented to normal-hearing subjects. Results show that the spectral centroid significantly affects the auditory impression concerning coolness and warmness; a higher spectral centroid induces a cooler auditory impression regardless of the room temperature.

Brain computer interface (BCI) technologies, which enable direct communication between the brain and external devices, have been developed. BCI technology can be utilized in neural prosthetics to restore impaired movement, including speech production. However, most of the BCI systems that have been developed are the "P300-speller" type, which can only detect objects that users direct his/her attention at. To develop more versatile BCI systems that can detect a user's intention or thoughts, the brain responses associated with verbal imagery need to be clarified. In this study, the brain magnetic fields associated with auditory verbal imagery and speech hearing were recorded using magnetoencephalography (MEG) carried out on 8 healthy adults. Although the magnetic fields lagged slightly and were long-lasting, significant deflections were observed even for verbal imagery, in the temporal regions, as well as for actual speech hearing. Also, sources for the deflections were localized in the association auditory cortices. Cross-correlations were calculated between envelopes of the imagined/presented speech sound and the evoked brain responses in the temporal areas. Measurable correlations were obtained for the presented speech sound; however, no significant correlations were observed for the imagined speech sound. These results indicate that auditory verbal imagery undoubtedly activates the auditory cortex, at least, and generates some observable neural responses.

To better understand the relationship between P-wave velocities and ice content in saturated, unconsolidated saline permafrost, we constructed an effective-medium model based upon ultrasonic P-wave data that were obtained from earlier laboratory studies. The model uses a two-end-member mixing approach in which an ice-filled, fully frozen end member and a water-filled, fully unfrozen end member are mixed together to form the effective medium of partially frozen sediments. This mixing approach has two key advantages: (1) It does not require parameter tuning of the mixing ratios, and (2) it inherently assumes mixed pore-scale distributions of ice that consist of frame-strengthening (i.e., cementing and/or load-bearing) ice and pore-filling ice. The model-predicted P-wave velocities agree well with our laboratory data, demonstrating the effectiveness of the model for quantitatively inferring ice content from P-wave velocities. The modeling workflow is simple and is largely free of calibration parameters - attributes that ease its application in interpreting field data sets.

Analytical models are provided that describe how the elastic compliance, electrical conductivity, and fluid-flow permeability of rocks depend on stress and fluid pressure. In order to explain published laboratory data on how seismic velocities and electrical conductivity vary in sandstones and granites, the models require a population of cracks to be present in a possibly porous host phase. The central objective is to obtain a consistent mean-field analytical model that shows how each modeled rock property depends on the nature of the crack population. The crack populations are described by a crack density, a probability distribution for the crack apertures and radii, and the averaged orientation of the cracks. The possibly anisotropic nature of the elasticity, conductivity, and permeability tensors is allowed for; however, only the isotropic limit is used when comparing to laboratory data. For the transport properties of conductivity and permeability, the percolation effect of the crack population linking up to form a connected path across a sample is modeled. However, this effect is important only in crystalline rock where the host phase has very small conductivity and permeability. In general, the importance of the crack population to the transport properties increases as the host phase becomes less conductive and less permeable.

Brain computer interface (BCI) technologies, which enable direct communication between the brain and external devices, have been developed. BCI technology can be utilized in neural prosthetics to restore impaired movement, including speech production. However, most of the BCI systems that have been developed are the "P300-speller" type, which can only detect objects that users direct his/her attention at. To develop more versatile BCI systems that can detect a user's intention or thoughts, the brain responses associated with verbal imagery need to be clarified. In this study, the brain magnetic fields associated with auditory verbal imagery and speech hearing were recorded using magnetoencephalography (MEG) carried out on 8 healthy adults. Although the magnetic fields lagged slightly and were long-lasting, significant deflections were observed even for verbal imagery, in the temporal regions, as well as for actual speech hearing. Also, sources for the deflections were localized in the association auditory cortices. Cross-correlations were calculated between envelopes of the imagined/presented speech sound and the evoked brain responses in the temporal areas. Measurable correlations were obtained for the presented speech sound; however, no significant correlations were observed for the imagined speech sound. These results indicate that auditory verbal imagery undoubtedly activates the auditory cortex, at least, and generates some observable neural responses.

A fluid-saturated flat channel between solids, such as a fracture, is known to support guided wavessometimes called Krauklis waves. At low frequencies, Krauklis waves can have very low velocity and large attenuation and are very dispersive. Because they propagate primarily within the fluid channel formed by a fracture, Krauklis waves can potentially be used for geological fracture characterization in the field. Using an analogue fracture consisting of a pair of flat slender plates with a mediating fluid layera trilayer modelwe conducted laboratory measurements of the velocity and attenuation of Krauklis waves. Unlike previous experiments using ultrasonic waves, these experiments used frequencies well below 1 kHz, resulting in extremely low velocity and large attenuation of the waves. The mechanical compliance of the fracture was varied by modifying the stiffness of the fluid seal of the physical fracture model, and proppant (fracture-filling high-permeability sand) was also introduced into the fracture to examine its impact on wave propagation. A theoretical frequency equation for the trilayer model was derived using the poroelastic linear-slip interface model, and its solutions were compared to the experimental results.

Determining the loudest sound that a person can comfortably tolerate (uncomfortable loudness level: UCL) is an important factor to be considered when designing sound intensity levels for devices such as hearing aids and those that generate notification signals. Although UCLs have been widely investigated using psychoacoustic methods, brain activity associated with them is not clear. To solve these problems, we measured magnetoencephalographic responses when participants passively listened to a series of tone bursts that varied in frequency and intensity. A psychoacoustic experiment was also performed on the same participants to obtain their subjective UCLs. Our results indicate that the amplitude and latency of the auditory evoked magnetic fields (AEFs) increased/decreased logarithmically as a function of increasing stimulus intensity level, and the subjective UCL appeared in the relaxation part of the change rate of AEFs. While no significant difference of tau(theta) (repetitive features within the signal) was observed as a function of stimulus intensity, the relationship between the neurophysiological signals (as indexed by the AEFs), spontaneous responses, and subjective UCL was captured and utilized to infer a model to estimate the UCL objectively.

Saline permafrost is sensitive to thermal disturbances and is prone to subsidence, which renders it a major source of geohazard in Arctic coastal environments. Seismic methods could be used to map and monitor saline permafrost at scales of geotechnical interests because of the ice-content dependencies of seismic properties. We have developed a comprehensive study of the ultrasonic P-wave properties (i.e., velocity and attenuation) of synthetic saline permafrost samples for a range of salinities and temperatures, and measurements conducted on a fine-grained permafrost core obtained from Barrow, Alaska. The resulting data consist of P-wave properties presented as functions of temperature and salinity. Notable observations include the following: P-wave velocities showed marked reductions in the presence of dissolved salts and complex variations resulting from the water-to-ice phase transitions; strong P-wave attenuation was present in the temperature intervals in which the samples were partially frozen. When presented as functions of ice saturation, the data sets lead us to two key findings: (1) neither a purely cementing nor a purely pore-filling model of the pore-scale distributions of ice could adequately fit the observed velocity data and (2) although the velocities increase monotonically with increasing ice saturations, P-wave attenuation reaches a maximum at intermediate ice saturations - contrary to the ordinary expectation of decreasing attenuation with increasing velocities. The observed ice-content dependencies of P-wave properties, along with the implications on the probable pore-scale distributions of ice, provide a valuable basis for rock-physics modeling, which in turn could facilitate seismic characterizations of saline permafrost.

We have been developing novel mobile phones using bone conduction, with flat-panel loudspeakers that convey speech sound by vibrating the pinna. In bone conduction via the pinna, i.e., pinna conduction, it is thought that speech sounds are conveyed via both air- and bone-conduction pathways. To obtain useful information for further development of bone-conduction mobile phones, peripheral mechanisms of the pinna conduction need to be clarified. In this study, hearing thresholds, sound field in the outer ear canals, and vibrations of the inner wall of the outer ear canals were measured while normal-hearing participants used pinna-conduction mobile phones.Thresholds decreased linearly as contact pressure increased below 1 kHz, but contact pressure did not affect thresholds above 2 kHz. Additionally, sound fields in the ipsilateral ear canal showed similar results. These results indicate that there is a considerable degree of bone-conduction components from the pinna to the inner ear, which only allow sounds below 1 kHz through. Because similar characteristics were observed in the threshold and the sound field in the outer ear canal, we suggest that osseotympanic emission, sound emission into the ear canal from the inner wall, and air conduction via external auditory foramen are the dominant components of pinna conduction.However, in the vibration measurement, differences between the ipsi- and contra-lateral responses were smaller than the sound field measurement. The smaller inter-lateral differences of the vibration in the outer ear canal suggest the existence of a significant amount of bone-conduction components that directly reach the middle or inner ear. Although the amount of such bone-conduction components does not seem sufficient for pinna

Objective: This study aimed to capture the neuronal frequency characteristics, as indexed by the auditory steady-state response (ASSR), relative to physical characteristics of constant sound pressure levels (SPLs). Relationship with perceptual characteristics (loudness model) was also examined.Methods: Neuromagnetic 40-Hz ASSR was recorded in response to sinusoidally amplitude-modulated sweep tones with carrier frequency covering the frequency range of 0.1-12.5 kHz. Sound intensity was equalized at 50-, 60-, and 70-dB SPL with an accuracy of +/- 0.5-dB SPL at the phasic peak of the modulation frequency. Corresponding loudness characteristics were modeled by substituting the detected individual hearing thresholds into a standard formula (ISO226: 2003(E)).Results: The strength of the ASSR component was maximum at 0.5 kHz, and it decreased linearly on logarithmic scale toward lower and higher frequencies. Loudness model was plateaued between 0.5 and 4 kHz.Conclusions: Frequency characteristics of the ASSR were not equivalent to those of SPL and loudness model. Factors other than physical and perceptual frequency characteristics may contribute to characterizing the ASSR.Significance: The results contribute to the discussion of the most efficient signal summation for the generation of the ASSR at 0.5 kHz and efficient neuronal processing at higher frequencies, which require less energy to retain equal perception. (C) 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Human listeners can perceive speech signals in a voice-modulated ultrasonic carrier from a bone-conduction stimulator even if the listeners are patients with sensorineural hearing loss. Taking this fact into account, we have developed a bone-conducted ultrasonic hearing aid (BCUHA). However, there remains considerable scope for improvement, particularly in terms of sound quality. Voice-modulated BCU is accompanied by a strong high-pitched tone and some distortion depending on the amplitude modulation method. In this study, the sound quality of a BCUHA with double-sideband transmitted carrier (DSB-TC) modulation and double-sideband suppressed carrier (DSB-SC) modulation methods was examined. The assessment was conducted by examining the transmission of the emotional state of the speaker. The evaluation used emotion-identification experiments. Types of emotion included Ekman&#039;s basic six emotions (“anger,” “disgust,” “fear,” “joy,” “sadness,” and “surprise”) and “neutral.” In addition, a series of subjective evaluations regarding “voice clarity,” “comfortableness,” and “preference” was conducted. The results showed that although DSB-SC sound was superior in “comfortableness” and “preference,” voice emotion transmission was more effective in DSB-TC conditions.

Birdsong is often used as an auditory signal for visually-challenged people in public spaces in Japan. However, more than 40% of visually-challenged people reported that such auditory signals were difficult to identify. We used auditory evoked magnetic field (AEF) responses in the human auditory cortex to uncover an auditory signal that was easy to identify. As an auditory signal, we focused on birdsong, which is currently used to inform passengers about the location of stairs in train stations in Japan. We presented birdsongs to participants in silent, noisy, reverberated, and interaural time-delay conditions. We analyzed the most prominent AEF response, N1m, and the correlation between the birdsong envelopes and the AEF. We found that the N1m amplitudes were maximal when the participants listened to the song of the Cuckoo and the above-mentioned correlation was maximal when the participants listened to the song of the Oriental Scops Owl. Thus, we believe the songs of the Cuckoo and Oriental Scops Owl to be candidates for optimal auditory signals. (C) 2015 Elsevier Ltd. All rights reserved.

A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AMBCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal. (C) 2015 The Japan Society of Applied Physics

Here, we propose a color barrier-free illumination consisting of white, red, and blue LEDs for people with deuteranopia-type defects in color perception. Color perceptions of 20 volunteers with normal vision and four examinees of deuteranopia were evaluated by both the Ishihara test for color blindness and the Farnsworth Panel D-15 test under color barrier-free illumination. The illumination was comparably effective, not only for discriminating between red and green but also for discrimination of the hues on a color chip continuously. (c) 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 218-223, 2015

Because body-conducted speech (BCS) sounds are conducted by skin, muscle, and bone and are not easily disrupted by airborne noises, noise-robust methods of speech detection using BCS have been developed. However, the intelligibility of BCS quickly deteriorates because it does not contain high-frequency components greater than 2 kHz. Thus, we previously proposed and evaluated a method that improves the sound quality of BCS using acceleration difference and noise reduction techniques. However, assessments based on human perception are essential. Consequently, in this paper, we report on evaluations conducted to verify the efficacy of the proposed method using word intelligibility tests and subjects with normal hearing.

Exposure to light modulates not only human alertness but also cognitive functions. The present study examined the temporal dynamics of the effects of light exposure on cortical activity related to cognitive processes. Event-related potentials (ERPs) were measured while participants performed an auditory oddball task during exposure to short-, medium- or long-wavelength light or darkness. Experiments were conducted in the daytime. After a 10-min period of darkness, one of the three lights was presented for 28 min. In the control condition, darkness was maintained for the entire session. The ERP component observed approximately 300 ms after the onset of the target stimulus (P300) was analyzed. The amplitude of P300 was larger after 5-20 min of exposure to short-wavelength light than at equivalent time points in the darkness. No differences were observed in the amplitude of P300 between the medium- or long-wavelength light condition and darkness at any time point. These results suggest that the amount of attentional resource allocated to the oddball task was increased by daytime exposure to short-wavelength light, and that following approximately 5 min of exposure the impact of light on cortical activity related to cognitive processes was able to be detected. (C) 2014 Elsevier Inc All rights reserved.

The Krauklis wave is a slow dispersive wave mode that propagates in a fluid layer bounded by elastic media. The guided properties of this wave and its ability to generate very short wavelengths at seismic frequency range predict possibility of resonances in fluid-filled rock fractures. Study of Krauklis wave properties at laboratory scales requires evaluation of its propagation velocities in models with finite and thin elastic walls. Analysis of an exact solution for a fluid-filled trilayer with equal thickness plates reveals existence of the Krauklis waves in such a model, as well as another mode which propagates mostly in the solid part. Both propagation modes exist at all frequencies. We derived and verified various asymptotic solutions by comparing their dependencies on layer thicknesses and frequency with the exact numerical solution. Analytical and computational results demonstrate that in a 60-cmlong model, the first resonant frequency can be below 10 Hz. This result suggests that the Krauklis-wave effects can be studied in a laboratory at seismic range of frequencies avoiding a notorious problem of frequency downscaling. Strong dispersive properties of Krauklis waves and their dominant behavior in fluid-fracture systems are likely phenomena explaining the observed frequency-dependent seismic effects in natural underground reservoirs.

The Krauklis wave is a slow dispersive wave mode that propagates in a fluid layer bounded by elastic media. The guided properties of this wave and its ability to generate very short wavelengths at seismic frequency range predict possibility of resonances in fluid-filled rock fractures. Study of Krauklis wave properties at laboratory scales requires evaluation of its propagation velocities in models with finite and thin elastic walls. Analysis of an exact solution for a fluid-filled trilayer with equal thickness plates reveals existence of the Krauklis waves in such a model, as well as another mode which propagates mostly in the solid part. Both propagation modes exist at all frequencies. We derived and verified various asymptotic solutions by comparing their dependencies on layer thicknesses and frequency with the exact numerical solution. Analytical and computational results demonstrate that in a 60-cmlong model, the first resonant frequency can be below 10 Hz. This result suggests that the Krauklis-wave effects can be studied in a laboratory at seismic range of frequencies avoiding a notorious problem of frequency downscaling. Strong dispersive properties of Krauklis waves and their dominant behavior in fluid-fracture systems are likely phenomena explaining the observed frequency-dependent seismic effects in natural underground reservoirs.

A novel hearing aid system based on bone-conducted ultrasonic (BCU) hearing is being developed for use by profoundly deaf people. However, the perception mechanisms involved in BCU hearing remain unclear. In this study, the way in which the mechanical frequency characteristics of human head vibration under BCU stimulation contribute to the hearing process was considered and examined in terms of the effects of the elasticity of the surface tissue that was in contact with a bone conduction vibrator. The results suggest that head vibration under BCU stimulation has low-pass filter-type characteristics with a cut-off frequency of between 30 and 40 kHz, which is attributed to the effects of the elasticity of living human skin. However, the issue of the psychoacoustic characteristics of the BCU hearing process not necessarily reflecting the mechanical frequency characteristics of head vibration remains. (C) 2014 The Japan Society of Applied Physics