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At least 73 records · Page 4Linked to original sources
PubMed2000

Effects of spectral complexity and sound duration on automatic complex-sound pitch processing in humans - a mismatch negativity study.

The pitch of a spectrally rich sound is known to be more easily perceived than that of a sinusoidal tone. The present study compared the importance of spectral complexity and sound duration in facilitated pitch discrimination. The mismatch negativity (MMN), which reflects automatic neural discrimination, was recorded to a 2. 5% pitch change in pure tones with only one sinusoidal frequency component (500 Hz) and in spectrally rich tones with three (500-1500 Hz) and five (500-2500 Hz) harmonic partials. During the recordings, subjects concentrated on watching a silent movie. In separate blocks, stimuli were of 100 and 250 ms in duration. The MMN amplitude was enhanced with both spectrally rich sounds when compared with pure tones. The prolonged sound duration did not significantly enhance the MMN. This suggests that increased spectral rather than temporal information facilitates pitch processing of spectrally rich sounds.

Adult↗
PubMed1996

Spatial tuning of neurons in the inferior colliculus of the big brown bat: effects of sound level, stimulus type and multiple sound sources.

We examined factors that affect spatial receptive fields of single units in the central nucleus of the inferior colliculus of Eptesicus fuscus. Pure tones, frequency- or amplitude-modulated sounds, or noise bursts were presented in the free-field, and responses were recorded extracellularly. For 58 neurons that were tested over a 30 dB range of sound levels, 7 (12%) exhibited a change of less than 10 degrees in the center point and medical border of their receptive field. For 28 neurons that were tested with more than one stimulus type, 5 (18%) exhibited a change of less than 10 degrees in the center point and medial border of their receptive field. The azimuthal response ranges of 19 neurons were measured in the presence of a continuous broadband noise presented from a second loudspeaker set at different fixed azimuthal positions. For 3 neurons driven by a contralateral stimulus only, the effect of the noise was simple masking. For 11 neurons driven by sound at either side, 8 were unaffected by the noise and 1 showed a simple masking effect. For the remaining 2, as well as for 5 neurons that were excited by contralateral sound and inhibited by ipsilateral sound, the peak of the azimuthal response range shifted toward the direction of the noise.

Acoustic Stimulation↗
PubMed1999

Effects of sound-field frequency modulation amplification on reducing teachers' sound pressure level in the classroom.

Voice problems are a frequent difficulty that teachers experience. Common complaints by teachers include vocal fatigue and hoarseness. One possible explanation for these symptoms is prolonged elevations in vocal loudness within the classroom. This investigation examined the effectiveness of sound-field frequency modulation (FM) amplification on reducing the sound pressure level (SPL) of the teacher's voice during classroom instruction. Specifically, SPL was examined during speech produced in a classroom lecture by 10 teachers with and without the use of sound-field amplification. Results indicated a significant 2.42-dB decrease in SPL with the use of sound-field FM amplification. These data support the use of sound-field amplification in the vocal hygiene regimen recommended to teachers by speech-language pathologists.

Adult↗
PubMed1984

Sound localization in large mammals: localization of complex sounds by horses.

The idea that large mammals localize sounds more accurately than small mammals has been noted frequently and is usually explained by reference to their large interaural distance and the correspondingly broad binaural time (delta t) and spectral (delta fi) differences between their two ears. Sound-localization thresholds for single clicks and 100-ms noise bursts were determined for horses, and the magnitude of the binaural time (delta t) and spectral (delta fi) cues for sound direction were measured on a horse. Although horses have relatively large interaural distances and physically broad binaural-localization cues available to them, their sound direction thresholds were markedly poorer than those of other large mammals--averaging 22 degrees for noise and 30 degrees for clicks. It appears that sound-localization acuity is not determined simply by the physical availability of binaural cues.

Animals↗
PubMedDate not supplied

[Sound reception of marine mammales depending on parameters and sound-conducting tracks].

Underwater audiograms of a northern fur seal, a Caspic seal and a dolphin aphalina were measured under conditions of full or partial (the head above the water) submergence of animals using the method of instrumental conditioned reflexes with food reinforcement. The possibility and peculiarities of sound conduction through the body of marine mammals were investigated by isolating the auricle from the medium of sound spreading (under conditions of partial submergence). By the same technique, the hearing thresholds of Caspic seal were measured in the presence of broad- and narrow-band noises with different central frequencies depending on the medium (underwater or in air) the signal and the noise masker were presented and on the sound-conducting ways (under conditions of full or partial submergence of animals). It was found that aerial and underwater sound-conducting canals of the Caspic seal were functionally connected with each other. The level of hearing masking in the Caspic seal is determined by the tracts of signal and noise conduction, by the differences in sensitivity to the signal and masker, and by their spectral structure. Apparently, the tissues of the seal body considerably change the amplitude-frequency characteristics of the sound.

Animals↗
PubMed1991

Sound field measurement tutorial. Working Group on Sound Field Calibration of the Committee on Audiologic Evaluation American Speech-Language-Hearing Association.

Although there are no standards or guidelines for sound field testing, it is recognized that such testing is an integral part of audiologic evaluation. This paper has reviewed some of the problems in sound field testing, as well as possible solutions to those problems. This review may be summarized as follows: 1. The environment in which sound field testing is conducted is an integral part of the test procedure; thus, the ambient noise and reverberation characteristics of the test room must be known. The test room must have ambient noise levels below the level at which the test signals will occur. 2. The listener must be seated so that the SPL of the test signal is known at that listener's pinna. Thus, care must be taken to exclude anything between the ear of the listener and the loudspeaker, and the height of the loudspeaker must be appropriate for the listener. (Note: If the loudspeakers are raised or lowered, it may be necessary to recalibrate.) The near/far field and direct/reverberant field boundaries should be identified and the listener positioned between those two boundaries. 3. The acoustic properties of the test signal must be defined clearly. An FM signal is best for assessing threshold of hearing. The examiner should measure the SPL and verify the spectral characteristics of the signal. The frequency of calibration measurements should be identical to that used for earphones, generally once every 3 months. Finally, it is important to understand the potential interaction between the test environment, the signal, and the listener when testing in the sound field. If the problems are understood and compensations are made it should be possible to obtain reliable and useful auditory information in the sound field.

Acoustics↗
PubMed2005

Non-contact sound speed measurement by optical probing of beam deflection due to sound wave.

We report a non-contact and non-invasive method of sound speed measurement by optical probing of deflected laser beam due to normally incident degenerated shock wave. In this study the shock wave from an exploding wire was degenerated to an ordinary sound wave at the distance exceeding 0.23 m. Temporal resolution of the deflected beam signal was improved by passing through an adequate electronic high-pass filter, as a result we obtained a better temporal resolution than that of the acoustic pressure detection by PZT transducer in terms of rising time. The spatial resolution was improved by passing the refracted beam signal into the edge of focusing lens to make a larger deflection angle. Sound speed was calculated by monitoring the time of flight of transient deflected signal at the predetermined position. Sound speed has been measured in air, distilled water and acryl, agreed well with the published values. The sound speed measured in the solution of glycerin, magnesium sulfate (MgSO4), and dimethylformamide with various mole fractions also agrees within 3% of relative error with those measured in the present work by ultrasonic pulse echo method. The results suggest that the method proposed is to be reliable and reproducible.

Journal Article↗
PubMed1997

Paradoxical lateral suppression in the dolphin's auditory system: weak sounds suppress response to strong sounds.

A paradoxical phenomenon was found in the auditory system of dolphins: weak sounds suppressed the brain responses to much stronger sounds. This occurred when the brain evoked potentials to rhythmic sound amplitude modulations were recorded. The response was markedly suppressed by addition of another sound of higher frequency and down to 40 dB lower intensity than the amplitude-modulated signal. Only the sustained rhythmic response was suppressed while transient on-response was not, thus indicating that the suppression influenced the ability of evoked potentials to follow rapid amplitude modulations. This prevents weak sounds from being masked by stronger ones. It may help a dolphin to perceive weaker echo-signals in the background of stronger emitted pulses.

Acoustic Stimulation↗
PubMed1999

Quantitative study of plasticity in the auditory nuclei of chick under conditions of prenatal sound attenuation and overstimulation with species specific and music sound stimuli.

Morphological effects of prenatal sound attenuation and sound overstimulation by species specific and music sounds on the brainstem auditory nuclei of chick have been evaluated quantitatively. Changes in length, volume, neuron number, size of neuronal nuclei and glial numbers of second and third order auditory nuclei, n. magnocellularis (NM) and n. laminaris (NL), were determined from thionine-stained serial sections of control and experimental groups on posthatch day 1 using stereological methods. Significant increase in volume of both auditory nuclei attributable to increase in length of nucleus, number and size of neurons, number of glia as well as neuropil was observed in response to both species specific and music overstimulation given during the critical period of development. The enhanced development of auditory nuclei in response to enriched environment prenatally indicates a positive effect of activity on neurons which may have clinical implications in addition to providing explanation for preference to auditory cues in the postnatal life. Reduction in neuron number with a small increase in proportion of cell nuclei of large size as well as an increase in glial numbers was seen in both NM and NL of the prenatally sound attenuated chicks. The increase in size of some neuronal nuclei may probably be evidence of enhanced synthesis of proteins involved in cell death or an attempt at recovery. The dissociated response of neurons and glia under sound attenuated and auditory stimulated conditions suggests that they are independently regulated by activity-dependent signals with glia also being under influence of other signals for a role in removal of dead cell debris.

Acoustic Stimulation↗
PubMed2003

A- and C-weighted sound levels as predictors of the annoyance caused by shooting sounds, for various façade attenuation types.

In a previous study on the annoyance caused by a great variety of shooting sounds [J. Acoust. Soc. Am. 109, 244-253 (2001)], it was shown that the annoyance, as rated indoors with the windows closed, could be adequately predicted from the outdoor A-weighted and C-weighted sound-exposure levels [ASEL (L(AE)) and CSEL (L(CE))] of the impulse sounds. The explained variance in the mean ratings by (outdoor) ASEL was significantly increased by adding the product (L(CE) - L(AE))(L(AE)) as a second variable. In the present study it was investigated to which extent the additional contribution of the second predictor is also relevant for façade attenuation types with lower and higher degrees of sound isolation than applied previously. Twenty subjects rated the indoor annoyance caused by 11 different impulse types produced by firearms ranging in caliber from 7.62 to 155 mm, at various levels and for five façade attenuation conditions. The effect of façade attenuation on the ratings was large and consistent. In all conditions, an optimal prediction of the annoyance was obtained with outdoor ASEL as the first, and (L(CE) - L(AE))(L(AE)) as the second predictor. The benefit of the second predictor, expressed as the increase in the explained variance, ranged from 2.5 to 55 percent points, and strongly increased with the degree of façade attenuation. It was concluded that for the determination of the rating sound level, the acoustic parameters ASEL and CSEL are very powerful. In addition, the results showed that for the whole set of impulses included, the annoyance could also be predicted very well by the weighted sum of indoor ASEL and the product (L(CE) - L(AE))(L(AE)).

Journal Article↗
PubMed2004

"The sound must seem an echo to the sense": Pope's use of sound to convey meaning in his translation of Homer's Iliad.

In his Essay on Criticism, Pope suggested that sound both could and should be used to convey meaning in poetry. To test his practice of this principle, the 52,000 sounds or phonemes in the first two Books of Pope's translation of the Iliad were scored with the help of Whissell's 2000 classification of sounds in terms of emotional meaning. A chi-squared contingency analysis indicated that there was a preferential and face valid use of Passive sounds in some passages and of Active sounds in others. There was also a significant difference between Books (Book I was more Active) and a distinct pattern of rise and then fall within each of them in the preferential use of Active phonemes.

Auditory Perception↗
PubMedDate not supplied

[Frequency discrimination by the bottle-nosed dolphin and the Northern fur seal depending on sound parameters and sound conduction pathways].

Underwater differential frequency hearing thresholds in the Black Sea bottle-nosed dolphin (Tursiops truncatus p.) and the northern fur seal (Callorhinus ursinus) were measured depending on signal frequency and sound conduction pathways. The measurements were performed by the method of instrumental conditioned reflexes with food reinforcement under conditions of full and partial (with heads out of water at sound conduction through body tissues) submergence of animals into water. It was shown that in a frequency range of 5-100 kHz, underwater differential frequency hearing thresholds of the bottle-nosed dolphin changed from 0.46-0.60% to 0.21-0.34% and depended little on sound conduction pathways. The minimum underwater differential frequency hearing thresholds of the northern fur seal corresponded to the frequencies of maximum hearing sensitivity, changed from 1.7% to 1-2.3% in a frequency range of 1-20 kHz, sharply increased at the edges of the frequency hearing perception range, and depended little (in a range of 5-40 kHz) on sound conduction pathways. Thus, underwater sounds propagating through the body tissues of dolphin and fur seal reach the inner ear.

Animals↗
PubMed1997

Adaptive reduction of heart sounds from lung sounds using fourth-order statistics.

When recording lung sounds, an incessant noise source occurs due to heart sounds. This noise source severely contaminates the breath sound signal and interferes in the analysis of lung sounds. In this paper, an adaptive heart-noise reduction method, based on fourth-order statistics (FOS) of the recorded signal, without requiring recorded "noise-only" reference signal, is presented. This algorithm uses adaptive filtering to preserve the entire spectrum. Furthermore, the proposed filter is independent of Gaussian uncorrelated noise and insensitive to the step-size parameter. It converges fast with small excess errors and, due to the narrow-band nature of heart noise (HN), it requires a very small number of taps. Results from experiments with healthy subjects indicate a local HN reduction equal to or greater than 90%.

Adaptation, Physiological↗
PubMed1990

[A quantitative study of TMJ sounds. 1. A systematization on frequency analysis of clicking sounds].

TMJ clicking sound is a sign worth noticing as prodromal symptoms of TMJ dysfunction. Therefore, a solution of its characteristics is an important matter to grasp the diagnosis of stomatognathic function and progress of the disease. We try to systematize the procedure from picking-up TMJ sound to convertion of frequency and then investigate picking-up method and the measurement apparatus, because we need a quantitation of acoustical components of clicking sound to examine the influence of hearing ability due to TMJ dysfunction. The following were obtained: 1. Low frequency noise is reduced by using headgear with microphone located in a external ear. 2. We pick up continuous 30 TMJ sounds three times in separate days. The waveforms of each set are approximately similar. 3. Each peak frequency and pattern of power spectrum examined three times show high correspondence. 4. The range of maximum peak frequencies in all subjects are from 0 to 0.8 KHz.

Auscultation↗
PubMed1986

Role of the dog's auditory cortex in discrimination of sound signals simulating sound source movement.

The ability of seven dogs to discriminate signal simulating sound source movement was studied using the avoidance technique. It was found that dogs can differentiate moving and stationary sound sources, and also discern the direction of the sound source movement. In addition, this study has defined the limits of the conditions under which sound source movement perception occurs. In each dog, unilateral ablation of the auditory cortex was followed by a localization deficit on the side contralateral to the ablation. Bilateral cortical lesions led to complete absence of the ability to discriminate source movement, simulated by changing stimulus interaural time differences. However, the dogs' ability to discriminate the movement after unilateral ablation by detecting interaural intensity differences was preserved, although their discriminative ability was lower than that of intact dogs.

Acoustic Stimulation↗
PubMed1997

Separation of discontinuous adventitious sounds from vesicular sounds using a wavelet-based filter.

The separation of pathological discontinuous adventitious sounds (DAS) from vesicular sounds (VS) is of great importance to the analysis of lung sounds, since DAS are related to certain pulmonary pathologies. An automated way of revealing the diagnostic character of DAS by isolating them from VS, based on their nonstationarity, is presented in this paper. The proposed algorithm combines multiresolution analysis with hard thresholding in order to compose a wavelet transform-based stationary-nonstationary filter (WTST-NST). Applying the WTST-NST filter to fine/coarse crackles and squawks, selected from three lung sound databases, the coherent structure of DAS is revealed and they are separated from VS. When compared to other separation tools, the WTST-NST filter performed more accurately, objectively, and with lower computational cost. Due to its simple implementation it can easily be used in clinical medicine.

Algorithms↗
PubMed2004

From symbols to sounds: visual symbolic information activates sound representations.

Expectations on forthcoming sounds can speed up responding to environmental changes and can, thus, be a basis for successful adaptation. The present study investigated event-related brain potential (ERP) effects in situations where particular sounds were predicted on the basis of preceding visual information. Subjects had to map scorelike visual symbols to corresponding sounds. The sounds could be either congruent or occasionally incongruent with the corresponding symbol. When the auditory stimulation was incongruent with the visual information, a brain response was elicited starting as early as about 100 ms from the onset of the auditory stimulus. It had a bilateral frontal distribution and a polarity inversion at the mastoids compatible with the assumption of sources in auditory cortex. These results suggest that the auditory system can establish a representation of an expected stimulus on the basis of visual symbolic information.

Acoustic Stimulation↗
PubMed2006

Sound source localization in real sound fields based on empirical statistics of interaural parameters.

The role of temporal fluctuations and systematic variations of interaural parameters in localization of sound sources in spatially distributed, nonstationary noise conditions was investigated. For this, Bayesian estimation was applied to interaural parameters calculated with physiologically plausible time and frequency resolution. Probability density functions (PDFs) of the interaural level differences (ILDs) and phase differences (IPDs) were estimated by measuring histograms for a directional sound source perturbed by several types of interfering noise at signal-to-noise ratios (SNRs) between -5 and +30 dB. A moment analysis of the PDFs reveals that the expected values shift and the standard deviations increase considerably with decreasing SNR, and that the PDFs have non-Gaussian shape at medium SNRs. A d' analysis of the PDFs indicates that elevation discrimination is possible even at low SNRs in the median plane by integrating information across frequency. Absolute sound localization was simulated by a Bayesian maximum a posteriori (MAP) procedure. The simulation is based on frequency integration of broadly tuned "detectors." Confusion patterns of real and estimated sound source directions are similar to those of human listeners. The results indicate that robust processing strategies are needed to exploit interaural parameters successfully in noise conditions due to their strong temporal fluctuations.

Acoustic Stimulation↗