Physiological evaluations of low-level impulsive sounds generated by an air conditioner.

Air conditioners are typically installed in buildings and vehicles to control thermal conditions for long periods of time. Air conditioners generate certain types of sounds while functioning, which are among the main noise sources in buildings and vehicles. Most sounds produced by the air conditioner do not change with time, and the sound quality of steady sounds has been investigated.

Induced brain magnetic activities related to salient birdsong under noisy conditions.

Objective: Birdsong sounds are often used to inform visually-challenged people about the presence of basic infrastructures, and therefore need to be salient in noisy urban environments. How salient sounds are processed in the brain could inform us about the optimal birdsong in such environments. However, brain activity related to birdsong salience is not yet known.

Subjective Salience of Birdsong and Insect Song with Equal Sound Pressure Level and Loudness.

Birdsong is used to communicate the position of stairwells to visually impaired people in train stations in Japan. However, more than 40% of visually impaired people reported that such sounds were difficult to identify. Train companies seek to present the sounds at a sound pressure level that is loud enough to be detected, but not so loud as to be annoying.

Spatiotemporal Characteristics of Cortical Activities Associated with Articulation of Speech Perception.

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.

Measurement of acoustic characteristics of Japanese Buddhist temples in relation to sound source location and direction.

Although temples are important buildings in the Buddhist community, the acoustic quality has not been examined in detail. Buddhist monks change the location and direction according to the ceremony, and associated acoustical changes have not yet been examined scientifically. To discuss the desired acoustics of temples, it is necessary to know the acoustic characteristics appropriate for each phase of a ceremony.

Listening level of music through headphones in train car noise environments.

Although portable music devices are useful for passing time on trains, exposure to music using headphones for long periods carries the risk of damaging hearing acuity. The aim of this study is to examine the listening level of music through headphones in the noisy environment of a train car. Eight subjects adjusted the volume to an optimum level (L(music)) in a simulated noisy train car environment.

Auditory evoked responses in human auditory cortex to the variation of sound intensity in an ongoing tone.

In daily life, variations of sound intensity, frequency, and other auditory parameters, can be perceived as transitions from one sound to another. The neural mechanisms underlying the processing of intensity change are currently unclear. The present study sought to clarify the effects of frequency and initial sound pressure level (SPL) on the auditory evoked response elicited by sounds of different SPL.

Effects of sound source location and direction on acoustic parameters in Japanese churches.

In 1965, the Catholic Church liturgy changed to allow priests to face the congregation. Whereas Church tradition, teaching, and participation have been much discussed with respect to priest orientation at Mass, the acoustical changes in this regard have not yet been examined scientifically. To discuss acoustic desired within churches, it is necessary to know the acoustical characteristics appropriate for each phase of the liturgy.

Temporal integration affects intensity change detection in human auditory cortex.

The aim of this paper was to clarify the effects of temporal integration on the auditory evoked response elicited by sounds of varying intensity. We measured auditory evoked fields in response to tones with different intervals of intensity change. The amplitude of the N1m', occurring approximately 100 ms after the intensity change, remained constant when the interval was longer than 250 ms.

Sound level-dependent growth of N1m amplitude with low and high-frequency tones.

The aim of this study was to determine whether the amplitude and/or latency of the N1m deflection of auditory-evoked magnetic fields are influenced by the level and frequency of sound. The results indicated that the amplitude of the N1m increased with sound level. The growth in amplitude with increasing sound level was almost constant with low frequencies (250-1000 Hz); however, this growth decreased with high frequencies (>2000 Hz).

Effects of center frequency on binaural auditory filter bandwidth in the human brain.

Effects of center frequency on the binaural auditory filter in the human auditory cortex were examined using auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli. Eight normal-hearing participants took part in the study.

The effects of pitch and pitch strength on an auditory-evoked N1m.

The aim of this paper was to determine whether the latency and/or amplitude of the N1m deflection of the auditory-evoked magnetic fields are influenced by the delay and number of iterations of iterated rippled noise, which are related to pitch and pitch strength, respectively. The results indicate that the N1m amplitude decreased sharply for delays between 16 and 32 ms, suggesting that the N1m amplitude reflects the lower limit of the audible pitch range. The N1m latency increases with increasing delay of up to 8-16 ms and then decreases again for delays longer than 16 ms.

Effects of the binaural auditory filter in the human brain.

The effects of the binaural auditory filter in the human auditory cortex were examined by auditory-evoked magnetic fields. Two tones with different frequency separations, which were presented dichotically to the left and right ears, were used as the sound stimuli, with all signals presented at sound pressure level of 60 dB. The results indicated that the N1m amplitudes were approximately constant when the frequency separation was less than 100 Hz; however, the N1m amplitudes increased with increasing frequency separation when the frequency separation was greater than 200 Hz.

Complex tone processing and critical band in the human auditory cortex.

Psychophysical experiments in humans have indicated that the auditory system has a well-defined bandwidth for resolution of complex stimuli. This bandwidth is known as the critical bandwidth (CBW). Physiological correlates of the CBW were examined in the human auditory cortex.

Auditory evoked magnetic fields in relation to interaural time delay and interaural correlation.

The detection of interaural time differences (ITD) for sound localization depends on the similarity between the left and right ear signals, namely interaural correlation (IAC). Human localization performance deteriorates with decreasing IACs. In order to examine activity related to localization performance in the human cortex, auditory evoked magnetic fields to the ITD of bandpass noises with different IACs were analyzed.

The effect of center frequency and bandwidth on the auditory evoked magnetic field.

Auditory evoked magnetic fields in relation to the center frequency of sound with a certain bandwidth were examined by magnetoencephalography (MEG). Octave band, 1/3 octave band, and 130 Hz bandwidth noises were used as the sound stimuli. All signals were presented at 60 dB SPL.

The optimal method for recording prosthetic heart valve sounds in clinical situations.

Background: Valve sounds are thought to be useful in evaluating the functioning of prosthetic heart valves. In previous reports, two recording instruments have mainly been used, a condenser microphone (instrument A) and an accelerometer (instrument B), respectively. This study aimed to investigate the applicability of these conventional devices in recording mechanical heart valve sounds in daily clinical situations.

Effects of the frequency of interaural time difference in the human brain.

The two cues to the horizontal location sound sources are interaural time differences and interaural level differences. For low-frequency tones, interaural time differences provide effective and unambiguous information. For higher frequency sounds, however, interaural time differences provide ambiguous cues.

Effects of the critical band on auditory-evoked magnetic fields.

Changes in the bandwidth affect the perceived loudness of a stimulus even when the level of the stimulus remains fixed. If the bandwidth of a sound is varied while maintaining the overall intensity, the loudness remains constant as long as the bandwidth is less than the critical bandwidth. If the bandwidth is increased beyond the critical bandwidth, the loudness increases with increasing bandwidth.

Effects of the degree of fluctuation on subjective preference for a 1 Hz flickering light.

Humans are believed to have a preferred amount of stimulus variation in their perceptual environment. Here, paired comparison tests were conducted to examine whether the fluctuation of a flickering light improves subjective preference. Sine-wave and bandpass noise acted as the light source.

Auditory evoked fields to variations of interaural time delay.

Auditory motion can be simulated by presenting binaural sounds with time-varying interaural time delays. Human cortical responses to the rate of auditory motion were studied by recording auditory evoked magnetic fields with a 122-channel whole-head magnetometer. Auditory motion from central to right and then to central was produced by varying interaural time differences between ears.

Auditory evoked magnetic fields in relation to iterated rippled noise.

Auditory evoked magnetic fields in relation to iterated rippled noise (IRN) were examined by magnetoencephalography (MEG). IRN was used as the sound stimulus to control the peak amplitude of the autocorrelation function of the sound. The IRN was produced by a delay-and-add algorithm applied to bandpass noise that was filtered using fourth-order Butterworth filters between 400-2200 Hz.

Auditory evoked magnetic fields in relation to bandwidth variations of bandpass noise.

Auditory evoked magnetic fields in relation to the bandwidth of bandpass noise were examined by magnetoencephalography (MEG). Pure tone and bandpass noises with center frequencies of 500, 1000 or 2000 Hz were used as the auditory signals. All source signals had the sound pressure level set at 74 dB.

Auditory evoked magnetic fields in relation to interaural cross-correlation of band-pass noise.

Auditory evoked magnetic fields of the human brain were analyzed in relation to the magnitude of the inter-aural cross-correlation (IACC). IACC of the stimuli was controlled by mixing diotic bandpass and dichotic independent bandpass noise in appropriate ratios. The auditory stimuli were binaurally delivered through plastic tubes and earpieces inserted into ear canals of the nine volunteers with normal hearing who took part in this study.