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PubMed2001

Algorithms for the generation of complex sounds for auditory physiology studies.

The pallid bat (Antrozous pallidus) is a member of a small class of bats known as gleaners. These bats use echolocation to avoid obstacles in flight while using passive listening to localize terrestrial prey. The echolocation pulses are 60-30 KHz downward frequency modulated sweeps that last 3-5 milliseconds. The prey-generated sounds are broadband noise transients in the 5-35 KHz range [1]. The frequency components of these sounds are beyond the range of commonly available sound cards, but the availability of fast, low-cost computers makes it possible to use host-based digital signal processing techniques to generate more complex sound patterns using existing equipment. The new capabilities allow new types and combinations of behaviorally relevant sounds to be generated, permitting the functions and topology of the auditory cortex to be mapped with increased detail. This paper describes the algorithms used to generate the amplitude and frequency modulated tones and band-pass filtered noise signals used as stimulus sounds.

Animals↗
PubMed2001

Temporal integration of sound pressure determines thresholds of auditory-nerve fibers.

Current propositions of the quantity of sound driving the central auditory system, specifically around threshold, are diverse and at variance with one another. They include sound pressure, sound power, or intensity, which are proportional to the square of pressure, and energy, i.e., the integral of sound power over time. Here we show that the relevant sound quantity and the nature of the threshold can be obtained from the timing of the first spike of auditory-nerve (AN) fibers after the onset of a stimulus. We reason that the first spike is triggered when the stimulus reaches threshold and occurs with fixed delay thereafter. By probing cat AN fibers with characteristic frequency tones of different sound pressure levels and rise times, we show that the differences in relative timing of the first spike (including latencies >100 msec of fibers with low spontaneous rates) can be well accounted for by essentially linear integration of pressure over time. The inclusion of a constant pressure loss or gain to the integrator improves the fit of the model and also accounts for most of the variation of spontaneous rates across fibers. In addition, there are tight correlations among delay, threshold, and spontaneous rate. First-spike timing cannot be explained by models based on a fixed pressure threshold, a fixed power or intensity threshold, or an energy threshold. This suggests that AN fiber thresholds are best measured in units of pressure by time. Possible mechanisms of pressure integration by the inner hair cell-AN fiber complex are discussed.

Acoustic Stimulation↗
PubMed2001

[Computer analysis of respiratory sounds in bronchial obstruction evaluation in small children that do not collaborate with spirometry tests].

BACKGROUND: There are changes in inspiratory breath sound intensity in patients with airway obstruction. Airway narrowing may change sound spectral characteristics. AIM: To define the characteristics of lung sounds at standardized air flow during methacholine challenge and to compare acoustic changes with transcutaneous oxygen tension (PtcO2) during induced airway narrowing. PATIENTS AND METHODS: Forty asthmatic children (20 male) aged 5.2 +/- 1 years and 40 normal children (18 male), aged 5.6 +/- 1 years were studied. All patients were free of respiratory tract infections one month before the study. A methacholine challenge from 0.06 to 8 mg/ml was performed; the test was ended when a fall in PtcO2 of > 20% from baseline was observed or if the final concentration was reached. Subjects breathed through a pneumotachograph aiming at flows of 0.4 to 0.6 l/s. Respiratory sounds were recorded using contact sensors at the suprasternal notch and at the posterior right lower lobe. From average spectra, power at low (100-200 Hz = P1) and high frequencies (400-2000 = P2) was calculated. Frequencies below which 50% (F50) and 99% (SEF90) of the spectral power between 100 and 2000 Hz was contained, were also calculated. RESULTS: In asthmatics, the metacholine concentration at which a 20% fall in PtcO2 was observed, was lower than in normal children (p < 0.05). There was an increase in P1 (p < 0.01) and a reduction in P2 (p < 0.01) during inspiration, in subjects that experienced a 20% reduction in PtcO2. Also, there was an increase in F50 and SEF99 during inspiration in lung sounds, but not over the trachea. CONCLUSIONS: Lung sounds analysis can be useful for the assessment of airway reactivity in asthmatic children.

Asthma↗
PubMed2005

[Sound transmission loss within the middle ear].

OBJECTIVE: To assess the amount of sound transmission loss in order to deeply understand the mechanism of middle ear sound transmission for ossicular reconstruction and for guidance of crimping between prosthesis and stapes on sound transmission in stapes surgery. METHODS: In order to get a correcting magnetic field 2 temporal bone models was used first. Temporal bone models was developed using 17 human temporal bones from fresh cadavers. To measure the sound transmission properties in the middle ear, 15 temporal bone models were detected by scanning laser Doppler interferometry with acoustical stimulation and electromechanical stimulation. An algorithm was developed to simulate acoustical stimulation with electromechanical stimulation. A sound transmission loss within the incudostapedial joint was detected by electromechanical stimulation in 10 temporal bone models. RESULTS: The average transmission loss within the incudostapedial joint remained 3 dB over the frequencies detected. CONCLUSIONS: There was a sound transmission loss within the incudostapedial joint, which was a physiological and protection way.

Acoustic Stimulation↗
PubMed2006

Early detection of pulmonary hypertension with heart sounds analysis pilot study.

There are strong evidences to support that the modification of the characteristics of the second heart sound has a high correlation with the pulmonary arterial pressure (PAP). It is hence postulated that a specific heart sound spectrum for this disease group could be generated as a decision support system to help healthcare workers for the early detection of pulmonary hypertension. This paper described the design of a case-control study on identifying the heart sound pattern of people with pulmonary hypertension. In the proposed study, the heart sound of patients having pulmonary hypertension will be captured by an electronic stethoscope and processed into digital sound spectra which will be analysed to identify a specific heart sound pattern. In the future, an intelligent device will be developed based on the identified pattern to identify and diagnose early stage of pulmonary hypertension.

Decision Support Systems, Clinical↗
PubMed1991

Sound localization and sensitivity to interaural time differences in human infants.

The role of interaural time differences in infants' sound localization was investigated. One experiment on free-field sound localization corroborated previous findings that the minimum audible angle changes substantially toward the end of the first half year after birth, and 3 experiments explored interaural time discrimination in that age range. The first of these 3 experiments used an adaptive psychophysical procedure, showing that infants responded appropriately in a sound lateralization task that provides a direct measure of interaural time discrimination. The other 2 experiments improved on the psychophysical procedure by taking into account the ceiling level on performance in the task. Infants aged 16, 20, and 28 weeks had thresholds in the range of 50 to 75 microsec, with no apparent age difference. These thresholds were much lower than would be predicted from studies of free-field sound localization, indicating that sensitivity to interaural time differences is not a limiting factor for the precision of sound localization in this age range. Instead, age-related changes in free-field sound localization may reflect the need to integrate across different localization cues and to calibrate the changing values of cues due to head growth.

Acoustic Stimulation↗
PubMed1991

An evaluation of the relationship between temporomandibular joint sounds and mandibular movements.

Mandibular movements in 28 subjects with TMJ sounds (who were otherwise asymptomatic) were evaluated and compared to those of 28 control subjects with no signs or symptoms of TM disorders (including the absence of clinically detectable TMJ sounds). Mandibular movements were recorded using the Sirognathograph interfaced with a personal computer. The joint sounds were recorded with contact microphones. The variables used to measure mandibular movements were not statistically different between the two groups except for mean mandibular deviation in the frontal plane, which was greater in the study group (3.2 mm) than the control group (2.2 mm). All combinations of mandibular movements were found to occur in relation to joint sounds with no obvious pattern. The large variability in both the study and control subjects, combined with the frequent finding of joint sounds in normal subjects, indicates that caution should be exercised in interpreting the characteristics of electronically recorded mandibular movements and TMJ sounds.

Adolescent↗
PubMed1990

Distress, jaw habits, and connective tissue laxity as predisposing factors to TMJ sounds in adolescents.

Immediately before a craniomandibular examination and measurement of wrist laxity, 96 adolescents answered a questionnaire about jaw habits, jaw activities, symptoms of stress, facial trauma, and TMJ sounds. The sample was divided into five subgroups on the basis of history and stethoscopically detected TMJ sounds. Some groups with TMJ sounds had significantly more jaw habits, jaw activities, and symptoms of stress than the control group (without history and clinically detected TMJ sounds). No significant differences emerged in angular measurement of wrist laxity between groups with TMJ sounds and the control group. This preliminary study indicates that an adolescent's distress may be associated with TMJ sounds. Further studies on subgroups of adolescents with different TMJ-related symptoms and signs are urged.

Adolescent↗
PubMed1989

[The effect of stressfully loud sound on motor asymmetry in rats].

In 43 female Wistar rats, a loud sound did not alter the asymmetry in behavioral tests even if is was loud enough to induce seizure. Under apomorphine test, the sound tended to decelerate the rotation, the asymmetry being preserved both in sound-activated and in sound-resistant subgroups. A shortening of the rotation onset latency occurred in sound-activated subgroup which may be associated with an increased permeability of the hemato-encephalic barrier following the sound-induced seizure.

Acoustic Stimulation↗
PubMed1989

Vision calibrates sound localization in developing barn owls.

This study demonstrates that continuous exposure of baby barn owls to a displaced visual field causes a shift in sound localization in the direction of the visual displacement. This implies an innate dominance of vision over audition in the development and maintenance of sound localization. Twelve owls were raised from the first day of eye opening wearing binocular prisms that displaced the visual field to the right by 11 degrees, 23 degrees, or 34 degrees. The prisms were worn for periods of up to 7 months. Consistent with previous results (Knudsen and Knudsen, 1989a), owls reared with displacing prisms did not adjust head orientation to visual stimuli. While wearing prisms, owls consistently oriented the head to the right of visual targets, and, as soon as the prisms were removed, they oriented the head directly at visual targets, as do normal owls. In contrast, prism-reared owls did change head orientation to sound sources even though auditory cues were not altered significantly. Birds reared wearing 11 degrees or 23 degrees prisms oriented the head to the right of acoustic targets by an amount approximately equal to the optical displacement induced by the prisms. Birds raised wearing 34 degrees prisms adjusted sound localization by only about 50% of the optical displacement. Thus, visually guided adjustment of sound localization appears to be limited to about 20 degrees in azimuth. The data indicate that when confronted with consistently discordant localization information from the auditory and visual systems, developing owls use vision to calibrate associations of auditory localization cues with locations in space in an attempt to bring into alignment the perceived locations of auditory and visual stimuli emanating from a common source. Vision exerts this instructive influence on sound localization whether or not visual information is accurate.

Animals↗
PubMed1989

[A digital filtering system for extracting crackles from lung sounds].

A nonlinear digital filter system is proposed for automatic extraction of crackles which are discontinuous adventitious sounds in lung sounds. This system is composed of two nonlinear digital filters; one is a stationary nonstationary separating filter, and the other is a width-discriminating filter. The former separates nonstationary signals from stationary ones in the lung sounds, using the prediction error to the input lung sound signal. If the prediction error is small enough, the lung sound is considered to be stationary, but if the error is large, a nonstationary signal is considered to occur and the nonstationary part is separated. The latter, the width-discriminating filter, performs signal extraction by considering the signal wave form of the crackles, simply realized by logical algebra. This filter extracts an impulsive signal, which is a small-width wave, and its succeeding waves; such wave form is typical of that of crackles. First, crackles are roughly separated by the stationary-nonstationary separating filter as nonstationary signals, and then are more precisely extracted from the nonstationary output by the width-discriminating filter. Some examples of processing actual lung sound data by this system show its high performance.

Filtration↗
PubMed1997

Spectrum analysis of respiratory sound: application to smokers and non-smokers.

Previous studies have indicated that respiratory sound signals may contain information useful in the detection of lung diseases. In this study, measurement and recordings of respiratory sound signal segments were obtained in normal subjects (non-smokers) and smokers in both inspiration and expiration phases. By using the autoregressive (AR) method, it is possible to produce power spectra of respiratory sound signals in inspiration and expiration phases for smokers and non-smokers of each group. The selection of the AR model order of the respiratory sound signals is achieved using Akaike criterion. The AR model order of 9 is required for completely described respiration sound signal segments in inspiration and expiration phases for both groups. The power spectra in the smoker group show larger distinct peaks at lower frequencies as well as more harmonics in both inspiration and expiration phases compared to the power spectra of the non-smoker group. Another diagnostic indicator was derived from the relative position of poles of the AR model of respiratory sound signals. In all smokers it was found that the first, third and fourth poles were closer to a unit circle than those in non-smokers (P < 0.01). It seems that the use of these indicators may be useful as early diagnostic tool for lung diseases.

Adult↗
PubMed1999

The effect of scanner sound in visual, motor, and auditory functional MRI.

The potentially important effect of gradient switching sound on brain function during functional magnetic resonance imaging (fMRI) was studied by comparing experiments with low and high scanner sound levels. To provide a low sound level experiment, a sparse scanning method was used, characterized by long, 9 sec, periods of scanner silence interspersed with 1 sec echoplanar imaging (EPI) bursts. For the condition with high sound levels, extra EPI gradient modules were inserted in the 9 sec inter-image intervals. Visual, motor, or auditory stimuli were presented in the interval between imaging. It was found that with the addition of gradient sounds, auditory activation was significantly decreased while motor and visual activation were not significantly altered. Other general factors relating to fMRI were also examined, such as experimental duration and fatigue. For example, motion of the subjects during the experiments was found to be related to the time spent in the scanner, rather than to the ambient sound level.

Acoustic Stimulation↗
PubMed2004

Auditory integration training and other sound therapies for autism spectrum disorders.

BACKGROUND: Autism spectrum disorders (ASD) are a heterogeneous group of disorders encompassing Autistic Disorder, Asperger's Disorder, Semantic-Pragmatic disorder and Pervasive Developmental Disorder Not Otherwise Specified. Auditory integration therapy (AIT) was developed as a technique for improving abnormal sound sensitivity in individuals with behavioural disorders including autism. Other sound therapies bearing similarities to AIT include the Tomatis Method and Samonas Sound Therapy. OBJECTIVES: To determine the effectiveness of AIT or other methods of sound therapy in individuals with ASD. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (Cochrane Library Issue 2, 2003), MEDLINE (1966 - February 2002), EMBASE (1980 - February 2002), CINAHL (1982 - December 2001), PsycINFO (1887 - February 2002), ERIC (1965 - December 2001) and LILACS (1982 - March 2002). Reference lists of articles identified electronically were searched for further relevant publications. SELECTION CRITERIA: Randomised controlled trials of adults or children with ASD. Treatment was auditory integration therapy (AIT) or other sound therapies involving listening to music modified by filtering and modulation. Control groups could be no treatment, waiting list, usual therapy or placebo equivalent. Outcomes sought were changes in core and associated features of ASD, auditory processing, quality of life and adverse events. DATA COLLECTION AND ANALYSIS: All outcome data reported in included papers were continuous. Initial intention was to undertake meta-analyses using mean difference and standard deviation to take into account differences between treatment and control groups at baseline. These data were not available. Instead, point estimates and standard errors were calculated from t-test scores and post intervention means. Meta-analysis was attempted but deemed inappropriate at present. MAIN RESULTS: No trials assessing sound therapies other than AIT were found. Six RCTs of AIT, including one cross-over trial, were identified with a total of 171 individuals aged 3-39 years. Four trials had fewer than 20 participants. Allocation concealment was inadequate for all of the studies. Seventeen different outcome measures were used. Only two outcomes were used by three or more studies: Aberrant Behaviour Checklist (ABC) (5) and Fisher's Auditory Problems Checklist (FAPC) (3). Meta-analysis was not possible due to very high heterogeneity (Aberrant Behaviour Checklist subscores), or presentation of data in unusable forms. Three studies (Bettison 1996, Zollweg 1997, Mudford 2000) did not demonstrate benefit of AIT over control conditions. The remaining trials (Veale 1993, Rimland 1995, Edelson 1999) reported improvements at 3 months for the AIT group based on improvements of total mean scores for the ABC, which is of questionable validity. Rimland 1995 also reported improvements at 3 months in the AIT group for ABC subgroup scores. No significant adverse effects of AIT were reported. REVIEWER'S CONCLUSIONS: More research is needed to inform parents', carers' and practitioners' decision making about this therapy for individuals with autism spectrum disorders.

Acoustic Stimulation↗
PubMed2000

Colony sound facilitates sexual and agonistic activities in royal penguins.

A unique playback system was used to exaggerate continuously the number of calls heard in royal penguin, Eudyptes schlegeli, colonies to determine whether social facilitation increases a female's exposure to both sexual and agonistic activities, a process that could influence the timing of reproduction in colonies. We also determined whether the source of colony sound or the phase of the breeding cycle influenced the facilitation of sexual or agonistic activities. The system recorded and then played a new 12-min colony sound sample every 24 min throughout the first four phases of the breeding cycle. Because each broadcast was unique, this playback system avoids the possibility of habituation and can modify the acoustic environment in social groups for extended periods of time. The activities of penguins in control colonies (with no playback) were compared with those in colonies that heard samples derived from either their own or a different colony. Colony sound facilitated both sexual and agonistic activities from male and female royal penguins during all four phases of the cycle that we examined. Playbacks from the perceiver's own colony facilitated a greater response than sound originating from a different colony. Studies comparing egg-laying dates in colonies exposed continuously to the sounds of agonistic activities with those in control colonies, or colonies exposed continuously to the sounds of sexual activities are now needed to determine whether the facilitation of agonistic activities opposes the effects of social stimulation on the hormonal changes leading to ovulation in colony-dwelling birds. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2001

Sound-localization experiments with barn owls in virtual space: influence of broadband interaural level different on head-turning behavior.

Interaural level differences play an important role for elevational sound localization in barn owls. The changes of this cue with sound location are complex and frequency dependent. We exploited the opportunities offered by the virtual space technique to investigate the behavioral relevance of the overall interaural level difference by fixing this parameter in virtual stimuli to a constant value or introducing additional broadband level differences to normal virtual stimuli. Frequency-specific monaural cues in the stimuli were not manipulated. We observed an influence of the broadband interaural level differences on elevational, but not on azimuthal sound localization. Since results obtained with our manipulations explained only part of the variance in elevational turning angle, we conclude that frequency-specific cues are also important. The behavioral consequences of changes of the overall interaural level difference in a virtual sound depended on the combined interaural time difference contained in the stimulus, indicating an indirect influence of temporal cues on elevational sound localization as well. Thus, elevational sound localization is influenced by a combination of many spatial cues including frequency-dependent and temporal features.

Acoustics↗
PubMed1988

Prevalence and characteristics of the aortic ejection sound in adults.

A survey of 1,950 phonocardiograms recorded over a 6-year period revealed 170 (9%) with a distinct aortic ejection sound. All patients were men with a mean age of 61 years (range 29 to 88). Associated clinical features were: aortic stenosis in 28%, history of systemic hypertension in 10%, history of rheumatic fever in 4% and none of these features in 58% of patients. In 141 (83%) of 170 patients the aortic ejection sound occurred simultaneously with or 0.01 second before or after the onset of the rise of the externally recorded carotid pulse. In 37 (66%) of 56 patients who had simultaneous echocardiograms and phonocardiograms recorded, the aortic ejection sound occurred at 0.01 second before or after the maximal opening point of the aortic valve leaflets. Two-dimensional echocardiography was performed in all patients and a bicuspid aortic valve was identified in 38 patients (22%). In 83 patients (49%) 3 cusps were clearly seen. In 49 patients (29%) an accurate determination was not possible. Anatomic examination of 120 consecutive aortic valves at autopsy was performed to identify possible causes of the aortic ejection sound. In 18 (15%) of autopsies fusion of 2 aortic cusps extending greater than or equal to 5 mm from the attachment to the aorta was observed. This abnormality, aortic commissural fusion, may be congenital or acquired. It is concluded that aortic ejection sounds may occur in patients without bicuspid aortic valves and in a variety of clinical conditions. A moderate degree of cuspal fusion may be the cause of the sound.

Adult↗
PubMed1989

Increase in the activity of tryptophan hydroxylase from cortex and midbrain of male Fischer 344 rats in response to acute or repeated sound stress.

Exposure of male Fischer 344 rats to an acute sound stress consisting of 100 dB tones of 2-s duration presented at random 60-s intervals for 2 h, increased cortical and midbrain tryptophan hydroxylase activity, measured in vitro, 50% over that from sham-stressed animals. This increase in enzyme activity was observed when animals were killed immediately, but not 1 h, after termination of the sound stress. It was non-additive with the increase in activity induced by incubation of enzyme under phosphorylating conditions and could be reversed in vitro with alkaline phosphatase. Graded increases in enzyme activity were obtained with increments of sound intensity (90-120 dB). In contrast to acute stress, chronic sound stress (110 dB) repeated over a period of 1, 2 or 6 weeks (3 sessions per week each of 2-h duration) produced a 50% increase in cortical enzyme activity that persisted 24 h after the termination of the stress and was not reversed by alkaline phosphatase. However, a further increase in enzyme activity could be produced if the chronically stressed animals were exposed to an acute 2-h stress (110 dB) immediately before being killed. This additional increase in activity was reversible in vitro by alkaline phosphatase and non-additive with that produced by incubation under phosphorylating conditions. In summary, acute sound stress produced a prompt, reversible activation of tryptophan hydroxylase. Repeated exposure to sound stress induced a persistent increase in enzyme activity that was detected 24 h after the last stress.

Acoustic Stimulation↗