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At least 1,459 records · Page 81Linked to original sources
PubMed2006

Frontal cortex functional connectivity changes during sound categorization.

Using functional connectivity analysis of functional magnetic resonance imaging data, we investigated the role of the inferior frontal gyrus in categorization of simple sounds. We found stronger functional connectivity between left inferior frontal gyrus and auditory processing areas in the temporal cortex during categorization of speech (vowels, syllables) and nonspeech (tones, combinations of tones and sweeps) sounds relative to an auditory discrimination task; the hemispheric lateralization varied depending on the speech-like properties of the sounds. Our results attest to the importance of interactions between temporal cortex and left inferior frontal gyrus in sound categorization. Further, we found different functional connectivity patterns between left inferior frontal gyrus and other brain regions implicated in categorization of syllables compared with other stimuli, reflecting the greater facility for categorization of syllables.

Acoustic Stimulation↗
PubMedDate not supplied

Sound field audiometry: recommended stimuli and procedures.

Comprehensive recommendations are presented for conducting sound field audiometry with frequency specific stimuli. These recommendations are primarily based on a series of investigations by the authors. The rationale for each recommendation is presented, together with a brief overview of the supporting research. The preferred stimuli are frequency modulation tones, triangularly or sinusoidally modulated at a rate of about 20 Hz, or suitably generated narrow bands of noise. The optimal bandwidths of the stimuli, expressed in percentages of the center frequency, vary with frequency. Stimuli suitable for most purposes have bandwidths ranging from about 30% at 0.25 kHz to about 10% at 4 kHz. Stimuli having narrower or broader bandwidths are desirable for some special purposes. The test room should be as nonreverberant as possible and the subject should be seated on an adjustable height chair with headrest. The control microphone method of calibration is preferred but a method is also presented for carrying out the traditional precalibration procedure. The SPL of the complex stimulus should be taken as the peak deflections on a sound level meter set to "RMS-FAST." A conversion table is presented which allows thresholds obtained in the sound field to be expressed as dB HTL. With the materials and methods described here it is possible to achieve the same reliability for sound field testing as for audiometry under earphones.

Acoustic Stimulation↗
PubMed2001

The effect of the audallion BEAMformer noise reduction preprocessor on sound localization for cochlear implant users.

OBJECTIVE: To assess the effect of the Audallion BEAMformer noise reduction preprocessor on the sound localization ability of children fitted unilaterally with the Nucleus 22-channel cochlear implant. DESIGN: Eight children aged 11 to 14 yr participated. Using three arrays of six loudspeakers, each child was tested in a semi-reverberant sound proof booth representative of a small office environment. The six loudspeakers were positioned 30 degrees apart in the horizontal plane at a distance of 1 m, spanning 150 degrees either directly in front of or to the left or right of the subject. The stimulus to be localized was a 300 msec broadband noise with a rise/decay of 50 msec. Subjects were tested with the BEAMformer in four possible settings, including one single microphone control condition, with each of the three loudspeaker arrays. One block of 60 forced-choice speaker identification trials was presented for each of the 12 listening conditions. On each trial, the stimulus was emitted by one of the six loudspeakers, randomly selected. RESULTS: Results demonstrated that subjects were unable to discriminate among sound sources arrayed horizontally in space using the cochlear implant microphone alone, or in combination, with the BEAMformer microphone located on the other ear. Results also showed that using the BEAMformer did not bias the perception of spatial location. CONCLUSIONS: The localization of acoustic stimuli in pediatric cochlear implant users was unaffected by the use of the Audallion BEAMformer. The apparent origin of most sounds appears to be pulled toward the implanted ear. Further studies are needed to validate findings.

Acoustic Stimulation↗
PubMed2001

Alternative voice after laryngectomy using a sound-producing voice prosthesis.

OBJECTIVE: To improve the voice quality of female laryngectomees and/or laryngectomees with a hypotonic pharyngoesophageal (PE) segment by means of a pneumatic artificial source of voice incorporated in a regular tracheoesophageal (TE) shunt valve. STUDY DESIGN: Experimental, randomized, crossover trial. METHODS: The new sound source consists of a single silicone lip, which performs an oscillatory movement driven by expired pulmonary air flowing along the outward-striking lip through the TE shunt valve. A prototype of this pneumatic sound source is evaluated in vitro and in six laryngectomees. In vivo evaluation includes speech rate, maximal phonation time, perceptual voice evaluation of read-aloud prose by an expert listener, speech intelligibility measurements with 12 listeners, and self-assessment by the patients. Moreover, extensive acoustical and aerodynamic in vivo registrations are performed using a newly developed data acquisition system. RESULTS: The current prototype seems beneficial in female laryngectomees with a hypotonic PE segment only. For them the sound-producing voice prosthesis improves voice quality and increases the average pitch of voice, without decreasing intelligibility or necessitating other pressure and airflow rates than regular TE shunt speech. Pitch regulation of this prosthetic voice is possible, yet limited. CONCLUSIONS: The mechanism is feasible and does not result in unacceptable airflow resistance. For this new mechanism of alaryngeal voice to become an established technique for postlaryngectomy voice restoration, a voice suitably pitched for male laryngectomees has to be generated and a large part of the melodic and dynamic range of the sound source has to be attainable within physiological airflow rates.

Aged↗
PubMed2003

Reliability and validity of judgments of sound quality in elderly hearing aid wearers.

OBJECTIVE: The aim of the present study was to evaluate a particular sound-quality rating procedure, referred to here as the Judgments of Sound Quality (JSQ) test, for potential use as an outcome measure with elderly hearing aid wearers. The validity and reliability of the JSQ as an outcome measure were determined for unaided and aided listening conditions. DESIGN: A repeated-measures design was employed with two primary independent variables, each with two values: 1) aided condition (aided versus unaided listening); and 2) trial (test versus retest). Sixteen elderly, hearing-impaired hearing aid users participated in the study. The participants provided ratings on eight dimensions of sound quality (softness, brightness, clarity, fullness, nearness, loudness, spaciousness, and total impression) under four stimulus conditions (speech at 65 dB SPL with a +8 dB signal-to-noise ratio, speech at 65 dB SPL in quiet, music at 90 dB SPL, and music at 75 dB SPL). Test and retest ratings were obtained in both unaided and aided conditions. RESULTS: No significant differences were found between median test and retest scores on the JSQ. The median ratings for each sound-quality dimension were found to have moderate test-retest reliability, with test-retest correlations (r) ranging from 0.20 to 0.73 (median r value = 0.58) for the unaided listening condition, and from 0.23 to 0.85 (median r value = 0.51) for the aided listening condition. Test validity was established through significant differences in JSQ ratings for various stimulus pairs (e.g., speech in quiet versus speech in noise). In addition, significant differences were observed between unaided and aided ratings for the dimensions of clarity, nearness, loudness, and total impression with aided JSQ ratings approaching normative "ideal" values established previously. CONCLUSIONS: The JSQ appears to be a potentially useful measure of hearing aid outcome, especially when using group data to document the benefits of amplification. Additional efforts should be directed at improving the reliability of the JSQ, however, before application to hearing aid wearers on an individual basis.

Aged↗
PubMed2006

Requirement of the auditory association cortex for discrimination of vowel-like sounds in rats.

We investigated the roles of the auditory cortex in discrimination learning of vowel-like sounds consisting of multiple formants. Rats were trained to discriminate between synthetic sounds with four formants. Bilateral electrolytic lesions including the primary auditory cortex and the dorsal auditory association cortex impaired multiformant discrimination, whereas they did not significantly affect discrimination between sounds with a single formant or between pure tones. Local lesions restricted to the dorsal/rostral auditory association cortex were sufficient to attenuate multiformant discrimination learning, and lesions restricted to the primary auditory cortex had no significant effects. These findings indicate that the dorsal/rostral auditory association cortex but not the primary auditory cortex is required for discrimination learning of vowel-like sounds with multiple formants in rats.

Acoustic Stimulation↗
PubMed2004

Fast sound in expanded fluid Hg accompanying the metal-nonmetal transition.

The dynamic structure factor S(Q,omega) of expanded fluid Hg has been measured up to the metal-nonmetal transition region at 9.0 g cm(-3) (1723 K and 1940 bars) using high-resolution inelastic x-ray scattering, at momentum transfers, Q, from 0.2 to 4.8 A(-1). Analysis in the framework of generalized hydrodynamics reveals that the frequencies of the collective excitations increase faster with Q than estimated from the macroscopic speed of sound. The effective sound velocity at 9.0 g cm(-3) estimated from the dispersion relation is triple the ultrasonic sound velocity. The present result suggests the existence of fast sound in expanded fluid Hg accompanying the metal-nonmetal transition.

Mercury↗
PubMed1992

The synthesis of the aortic valve closure sound of the dog by the mean filter of forward and backward predictor.

The application of a new algorithm, the mean filter of forward and backward predictor, to synthesize the aortic component of the second heart sound (A2), according to an exponentially damped sinusoid model, is described. The resulting estimates of four modeling parameters composing each sinusoid of A2 (amplitude, damping factor, frequency, and phase) were used to synthesize the original aortic sounds. The synthesized sounds were then compared to the original sounds recorded on the thorax of six dogs and an error index was computed. The results show that the method is more precise than the forward predictor filter, the backward predictor filter, and the improved KT algorithm. The new algorithm is also highly stable and the error index between the original A2 and the synthesized waveforms is always less than 1%.

Algorithms↗
PubMed1989

Separation of fine crackles from vesicular sounds by a nonlinear digital filter.

Crackles are discontinuous adventitious sounds, and their separation is an important process in the analysis of lung sounds. In order to separate the crackles from vesicular sounds automatically, we used a nonlinear digital filter which was designed to separate nonstationary from stationary signals. We applied this filter to the lung sounds recorded from six patients with pulmonary fibrosis. The separation was satisfactory enough to make this method useful in clinical medicine.

Diagnosis, Computer-Assisted↗
PubMed1995

Distribution of aortic mechanical prosthetic valve closure sound model parameters on the surface of the chest.

It has been previously proposed that heart valve closure sounds can be modeled by a sum of decaying sinusoids, based on the hypothesis that the heart cavity, heart walls, major vessels, and other structures in the chest constitute a frequency selective linear acoustic system and this system is excited by the rapidly decelerating valve occluder. In this study, distribution of the parameters of this model for the second heart sound is investigated. For this purpose, heart sounds of 10 patients who have a St. Jude-type bileaflet mechanical heart valve prosthesis in aortic position are recorded. Recordings are performed at 12 different locations on the surface of the chest. To reliably assign representative parameters to each recording site, signal averaging, model order selection, and a special filtration technique are employed. The results of the analyses are discussed in relation to the above hypothesis on the heart sound generation mechanism. It is observed that site-to-site variation of frequencies of modes does not exceed the accuracy limit of proposed analysis method, but energies of these modes vary on the surface of the chest, and as a result of statistical analysis, it appears that energy of some modes are significantly different between two recording sites.

Adolescent↗
PubMed1996

Spectral composition of heart sounds before and after mechanical heart valve implantation using a modified forward-backward Prony's method.

This paper investigates the impact of the lung-thorax and heart-valve system on the overall spectral composition of the externally recorded heart sounds. The study concentrates in the case of the first and the second heart sounds for normal patients and patients before and after implantation of a mechanical valve in the mitral or aortic position. The analysis is performed using a modified forward-backward overdetermined Prony's method (MFBPM) which uses a forward-backward mean filter and a modified procedure for estimating the position of the signal poles. In terms of the normalized cross-correlation coefficient, this method has an average modeling accuracy of 99.62% for representing the first and second heart sounds and an average least square time-domain error of 0.43%. Results obtained from 40 subjects show that the condition of the native mitral or aortic valve affects mostly the distribution of the amplitudes of the spectral components, whereas the number of the spectral components or their respective relative energy remains more or less unchanged. It has been found that the amplitudes of frequency components in the range 120-250 Hz are more affected by abnormalities of native mitral valves. Furthermore, in the case of the second heart sound the region 250-400 Hz has been found to be more affected by abnormalities in the aortic valve. It has also been found that the mechanical prosthetic heart valve affects mostly the spectrum beyond 400 Hz. A clear difference has been observed in the frequency spectrum above 400 Hz between both normally and abnormally functioning native valves and normally functioning mechanical valves. Preliminary results in some malfunctioning cases of mechanical prosthesis suggest that spectral components beyond 400 Hz can be used to monitor the condition of these prostheses.

Adult↗
PubMed2000

Computerized classification of temporomandibular joint sounds.

Sounds, such as clicking and/or crepitation, evoked in the temporomandibular (jaw) joint during function may indicate pathology. Analysis of the reduced interference time-frequency distribution of these sounds is of diagnostic value. However, visual evaluation is expensive and error prone, and there is, thus, a need for automated analysis. The aim of this study was to find the optimal signal representation and pattern recognition method for computerized classification of temporomandibular joint sounds. Concepts of time-shift invariance with and without scale invariance were employed and mutually compared. The automated analysis methods provided classification results that were similar to previous visual classification of the sounds. It was found that the classifier performance was significantly improved when scale invariance was omitted. This behavior occurred because scale invariance interfered with the frequency content of the signal. Therefore, scale invariance should not be pursued in the classification scheme employed in this study.

Biomedical Engineering↗
PubMed2000

Asthmatic airways obstruction assessment based on detailed analysis of respiratory sound spectra.

This paper concerns the analysis of adventitious sounds produced by individual asthmatic patients, and relates the sounds to the degree of airways obstruction at the moment of sound recording. In this study, airways obstruction is represented by a parameter commonly used in clinical tests, the forced expiratory volume in one second. A nonrestrictive approach using spectral information in detail is followed, resulting in a fairly high resolution of respiration sounds with respect to airways obstruction. The beneficial effect of a power raising transformation is presented, together with an illumination of the background of this effect.

Acoustics↗
PubMed1990

The transmission of ambient noise and self-generated sound in the human body.

It is commonly understood that ambient noise and sounds produced by a pregnant woman herself are propagated into the body and reach the unborn child in the uterus. However, it would be unethical to study the propagation of sound to the fetus directly, so the present study, which aimed to clarify this process from an acoustical point of view, used the stomach as a model of the womb. The following points were demonstrated: For sound waves in the stomach, no interference such as occurs outside the body was observed. However, in the range 2 to 3 kHz, a resonance peak was visible, which was probably due to the gastric air space. Observing an average spectrum of songs showed that the sound pressure level (SPL(dB)) in the medium to lower range (below 3 kHz) tended to be higher in the stomach than outside.

Female↗
PubMed2005

Sound-guided shaping of the receptive field in the mouse auditory cortex by basal forebrain activation.

The mammalian auditory cortex undergoes continuous plasticity following auditory experience. This study demonstrates the instructive roles of sound frequency and amplitude in representational plasticity in the primary auditory cortex of the mouse. Electrical stimulation of the basal forebrain paired with a tone led to a pronounced shift in the receptive field of the cortical neurons in both frequency and amplitude domains, the shift being towards the frequency and amplitude of the tone. Importantly, the plasticity in the frequency tuning of cortical neurons appeared to be largely dependent upon frequency-specific decreases in the response threshold. The minimum threshold of cortical neurons could be reduced only if the amplitude of the presented tone was lower than the minimum threshold. This finding suggests that training with low-intensity sound can increase the sensitivity of cortical neurons. Furthermore, all of these effects evoked by basal forebrain activation could be eliminated by cortical application of atropine, the acetylcholine muscarinic receptor antagonist. The data suggest that cortical plasticity is guided by both sound frequency and amplitude. The basal forebrain promotes sound-guided cortical plasticity by facilitating neural mechanisms intrinsic to the auditory system.

Acoustic Stimulation↗
PubMed1998

Which Korotkoff sound should be used for the diastolic blood pressure in pregnancy?

There is a gathering momentum favouring the adoption of the 5th Korotkoff sound to identify diastolic blood pressure in pregnancy. Our objective was to measure interobserver reliability for indirect blood pressure measurement in pregnancy for systolic and diastolic measurements and to calculate the difference in diastolic pressure measured by the 4th and 5th Korotkoff sounds. To minimize bias we used trained but previously inexperienced observers with proven, normal auditory acuity. The observers were paired in 4 teams and performed a series of 334 blinded, simultaneous observations of systolic and diastolic blood pressure measurements taken from pregnant women between 12-41 weeks' gestation. Reliability was measured by intraclass correlation coefficient for paired measures and kappa for the detection or nondetection of 4th (K4) and 5th (K5) Korotkoff sounds. K4 was undetected in 36% of observations and K5 was undetected in 2% of observations. Reliability for detection or nondetection of Korotkoff sounds was fair for K4 (kappa 0.36) and moderate for K5 (kappa 0.58). Reliability was good between observers for systolic, K4 and K5 diastolic measurements (intraclass correlation > or = 0.80). The mean difference between the diastolic pressure measured by K4 and K5 was 15 mmHg for all measurements and 8 mmHg for the top quartile of measurements (p <0.001). We found K5 to be more often and more reliably detected than K4. If units adopt K5 in preference to K4, consideration will need to be given to lowering treatment thresholds for women with borderline or mild hypertension.

Adult↗
PubMed2006

Estimation of early-stage malfunction using implantable artificial heart sound in animal experiments.

We have developed an automatic diagnosis system of an artificial heart in order to ensure the safety of the patient implanted with the artificial heart. The automatic diagnosis system is composed of an electro-stethoscope system, adaptive noise canceller (ANC), and artificial neural network (ANN). The ANC effectively eliminates ambient noise from the sound signal of the artificial heart detected by the electro-stethoscope, and a filtered sound signal is separated into each frequency components by fast Fourier transformation. Each frequency component of an artificial heart's acoustic signal is fed into the ANN in order to make a diagnosis of pump condition. The automatic diagnosis system was evaluated in mock circulatory tests and a long-term animal experiment using a goat implanted with an undulation pump ventricular assist device (UPVAD). In mock circulatory tests, the ANN was able to detect pump failing conditions, which were occlusion of inflow and outflow cannula and deterioration of the ball bearing. In a long-term animal experiment, after training the ANN using UPVAD's sound signal in normal condition, the diagnosis system continuously monitored UPVAD's sound signal detected by the electro-stethoscope placed on the surface of the left thoracic cavity of the goat. The UPVAD was stopped by rupture of a diaphragm in the pump on the ninth day of operation. We were able to identify initial signs of malfunction of the pump on the eighth day, while the UPVAD was able to operate normally. In conclusion, the automatic diagnosis system for malfunction of the artificial heart has enough performance to detect early stages of malfunction of the artificial heart, and it contributes to ensure the patient's safety.

Animals↗
PubMed2006

Mechanisms underlying the temporal precision of sound coding at the inner hair cell ribbon synapse.

Our auditory system is capable of perceiving the azimuthal location of a low frequency sound source with a precision of a few degrees. This requires the auditory system to detect time differences in sound arrival between the two ears down to tens of microseconds. The detection of these interaural time differences relies on network computation by auditory brainstem neurons sharpening the temporal precision of the afferent signals. Nevertheless, the system requires the hair cell synapse to encode sound with the highest possible temporal acuity. In mammals, each auditory nerve fibre receives input from only one inner hair cell (IHC) synapse. Hence, this single synapse determines the temporal precision of the fibre. As if this was not enough of a challenge, the auditory system is also capable of maintaining such high temporal fidelity with acoustic signals that vary greatly in their intensity. Recent research has started to uncover the cellular basis of sound coding. Functional and structural descriptions of synaptic vesicle pools and estimates for the number of Ca(2+) channels at the ribbon synapse have been obtained, as have insights into how the receptor potential couples to the release of synaptic vesicles. Here, we review current concepts about the mechanisms that control the timing of transmitter release in inner hair cells of the cochlea.

Afferent Pathways↗