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PubMed2003

Tracheal and lung sounds repeatability in normal adults.

Tracheal and lung sounds measurements for clinical applications depends on their intrasubject repeatability. Our objectives were to characterize tracheal and lung sounds and to investigate the temporal variability in normal adults. Tracheal sounds were studied in 7 subjects and lung sounds in 10 adults. Acoustic measurements were done in five occasions over a month for tracheal sounds and on seven occasions over a year for lung sounds. Sounds were recorded using contact sensors on the suprasternal notch and on the posterior right lower lobe. Subjects breathed through a pneumotachograph at flows of 0.9-1.1 l/s. Signals were low-pass filtered, amplified and Fourier analysis was applied to sounds within a target flow range. We measured the frequencies below which 25% (F25), 50% (F median), 75% (F75) and 99% (SEF99) of the spectral power between 100 and 2000 Hz. There were no differences between the measurements obtained at different days comparing each subject (P = ns, ANOVA). Our results show that the spectral pattern of tracheal and lung sounds are stable with low intrasubject variability.

Adult↗
PubMed2002

A common cortical substrate activated by horizontal and vertical sound movement in the human brain.

Perception of movement in acoustic space depends on comparison of the sound waveforms reaching the two ears (binaural cues) as well as spectrotemporal analysis of the waveform at each ear (monaural cues). The relative importance of these two cues is different for perception of vertical or horizontal motion, with spectrotemporal analysis likely to be more important for perceiving vertical shifts. In humans, functional imaging studies have shown that sound movement in the horizontal plane activates brain areas distinct from the primary auditory cortex, in parietal and frontal lobes and in the planum temporale. However, no previous work has examined activations for vertical sound movement. It is therefore difficult to generalize previous imaging studies, based on horizontal movement only, to multidimensional auditory space perception. Using externalized virtual-space sounds in a functional magnetic resonance imaging (fMRI) paradigm to investigate this, we compared vertical and horizontal shifts in sound location. A common bilateral network of brain areas was activated in response to both horizontal and vertical sound movement. This included the planum temporale, superior parietal cortex, and premotor cortex. Sounds perceived laterally in virtual space were associated with contralateral activation of the auditory cortex. These results demonstrate that sound movement in vertical and horizontal dimensions engages a common processing network in the human cerebral cortex and show that multidimensional spatial properties of sounds are processed at this level.

Acoustic Stimulation↗
PubMed1995

The influence of onset sound level of test stimulus on reported magnitude of changing-loudness aftereffects.

An increasing-loudness aftereffect follows adaptation to a tone of decreasing sound level; a decreasing-loudness aftereffect follows adaptation to a tone of increasing sound level. Contrary to the belief that sensory processing contributes to these changing-loudness aftereffects, evidence suggests that onset sound level of test stimulus may have little influence on reported aftereffects. This was tested formally in the present study. Adapting stimuli and test stimuli all employed 1-kHz sinusoidal carriers: Three onset sound levels of test stimuli were well within the range of sound levels encompassed by adapting stimuli; a fourth was set at the highest value of this range. Consistent with previous evidence, substantial aftereffects were reported for all the midrange onset sound levels, with little difference across onset sound levels. However, for the high-range onset sound level, reported aftereffects were severely attenuated. Sensory processing can be invoked by supposing that aftereffect mechanisms "tap" neural activity that encodes adapting sound levels.

Humans↗
PubMed1996

Quantitative analysis of sound localization with ocular positioning.

We studied the capacity for sound localization in the horizontal plane with measurement of the ocular position of the listener. The eye position responses elicited by tonal sound were asymmetrical in all six subjects and there was individual variation of frequency dependence. The sound pressure level and the angle of the loudspeaker also affected the accuracy of localization. Sound localization was more accurate, and individual variation lower, when the sound pressure level and the angle of the sound source were in the range 50 dBSL and 30 degrees, respectively. In the monoaural condition, the ear on the occluded side consistently showed displacement of responses toward the side of the non-occluded ear. Sound localization on the non-occluded side, however, showed various patterns of change in the monaural condition relative to the binaural condition. Cues as to the sound localization thus seem to differ with the side of the sound source.

Acoustic Stimulation↗
PubMed2003

Modeling and measurement of flow effects on tracheal sounds.

The analysis of breathing sounds measured over the extrathoracic trachea offers a noninvasive technique to monitor obstructions of the respiratory tract. Essential to development of this technique is a quantitative understanding of how such tracheal sounds are related to the underlying tract anatomy, airflow, and disease-induced obstructions. In this study, the first dynamic acoustic model of the respiratory tract was developed that takes into consideration such factors as turbulent sound sources and varying glottal aperture. Model predictions were compared to tracheal sounds measured on four healthy subjects at target flow rates of 0.5, 1.0, 1.5, and 2.0 L/s, and also during nontargeted breathing. Both the simulation and measurement spectra depicted increasing sound power with increasing flow, with smaller incremental increases at the higher flow rates. A sound power increase of approximately 30 dB between a flow rate of 0.5 and 2.0 L/s was observed in both the simulated and measured spectra. Variations of as much as 15 dB over the 300-600 Hz frequency band were noted in the sound power produced during targeted and nontargeted breathing maneuvers at the same flow rates. We propose that this variability was in part due to changes in glottal aperture area, which is known to vary during normal respiration and has been observed as a method of flow control. Model simulations incorporating a turbulent source at the glottis with respiratory cycle variations in glottal aperture from 0.64 cm2 to 1.4 cm2 explained approximately 10 dB of the measured variation. This study provides the first links between spatially distributed sound sources due to turbulent flow in the respiratory tract and noninvasive tracheal sounds measurements.

Acoustics↗
PubMed2000

The single sonic muscle twitch model for the sound-production mechanism in the weakfish, Cynoscion regalis.

A model of the weakfish, Cynoscion regalis, sound-production mechanism based on damped driven oscillators is presented. The weakfish "purr" consists of several short pulses of sound separated by intervals of no sound. Each pulse is produced by an individual simultaneous twitch of each sonic muscle causing swimbladder oscillations that radiate sound into the surrounding water. The sonic muscles are modeled as a stretched string with a time-varying tension force. The swimbladder is modeled as a highly damped, driven oscillator undergoing radial oscillations. Although the swimbladder functions as an impedance-matching device between the sonic muscles and the surrounding fluid, its transient response to the sonic muscle pulses includes frequencies that are not a part of the spectrum of the sonic muscle excitations. Differential equations of motion for the sonic muscles and swimbladder are given and are numerically solved to produce predicted waveforms matching those of measured weakfish sounds. The model leads to better understanding of the weakfish sound-producing mechanism and the effects of environmental and physiological factors on sound production. This model may also lead to a better understanding of sound production in other species, particularly other members of Family Sciaenidae, with similar mechanisms for sound production.

Air Sacs↗
PubMed2002

Empirical refinements applicable to the recording of fish sounds in small tanks.

Many underwater bioacoustical recording experiments (e.g., fish sound production during courtship or agonistic encounters) are usually conducted in a controlled laboratory environment of small-sized tanks. The effects of reverberation, resonance, and tank size on the characteristics of sound recorded inside small tanks have never been fully addressed, although these factors are known to influence the recordings. In this work, 5-cycle tone bursts of 1-kHz sound were used as a test signal to investigate the sound recorded in a 170-l rectangular glass tank at various depths and distances from a transducer. The dominant frequency, sound-pressure level, and power spectrum recorded in small tanks were significantly distorted compared to the original tone bursts. Due to resonance, the dominant frequency varied with water depth, and power spectrum level of the projected frequency decreased exponentially with increased distance between the hydrophone and the sound source; however, the resonant component was nearly uniform throughout the tank. Based on the empirical findings and theoretical calculation, a working protocol is presented that minimizes distortion in fish sound recordings in small tanks. To validate this approach, sounds produced by the croaking gourami (Trichopsis vittata) during staged agonistic encounters were recorded according to the proposed protocol in an 1800-l circular tank and in a 37-l rectangular tank to compare differences in acoustic characteristics associated with tank size and recording position. The findings underscore pitfalls associated with recording fish sounds in small tanks. Herein, an empirical solution to correct these distortions is provided.

Acoustics↗
PubMed1995

Significant differences in flow standardised breath sound spectra in patients with chronic obstructive pulmonary disease, stable asthma, and healthy lungs.

BACKGROUND: Spectral characteristics of breath sounds in asthma and chronic obstructive pulmonary disease (COPD) have not previously been compared, although the structural differences in these disorders might be reflected in breath sounds. METHODS: Flow standardised inspiratory breath sounds in patients with COPD (n = 17) and stable asthma (n = 10) with significant airways obstruction and in control patients without any respiratory disorders (n = 11) were compared in terms of estimates of the power spectrum. Breath sounds were recorded simultaneously at the chest and at the trachea. RESULTS: The median frequency (F50) of the mean (SD) breath sound spectra recorded at the chest was higher in asthmatics (239 (19) Hz) than in both the control patients (206 (14) Hz) and the patients with COPD (201 (21) Hz). The total spectral power of breath sounds recorded at the chest in terms of root mean square (RMS) was higher in asthmatics than in patients with COPD. In patients with COPD the spectral parameters were not statistically different from those of control patients. The F50 recorded at the trachea in the asthmatics was significantly related to forced expiratory volume in one second (FEV1) (r = -0.77), but this was not seen in the other groups. CONCLUSIONS: The observed differences in frequency content of breath sounds in patients with asthma and COPD may reflect altered sound generation or transmission due to structural changes of the bronchi and the surrounding lung tissue in these diseases. Spectral analysis of breath sounds may provide a new non-invasive method for differential diagnosis of obstructive pulmonary diseases.

Adult↗
PubMed1978

Accentuation of heart sounds in anemia: an effect of blood viscosity.

The effect of blood viscosity on the intensity of heart sounds was investigated in 25 anemic patients and 41 control subjects. Calibrated phonocardiograms showed that in anemic patients, the aortic component of the second sound was of greater amplitude (54 +/- 3 vs. 33 +/- 3 dyn/cm2) (P less than 0.001). The pulmonary component of the second sound and the first sound were also of higher amplitude in anemic patients (both P less than 0.001). The viscosity of blood of anemic patients was lower (0.029 +/- 0.001 vs. 0.045 +/- 0.001 poise) (P less than 0.001). Blood pressure was comparable among the two groups. Sound produced by closure of a normal porcine valve in an in vitro flow system also showed an accentuated sound with liquids of lower viscosity. Augmented diastolic vibrations of the closed valve, shown by high-speed motion pictures, accompanied the accentuated sound. These observations suggest that the accentuated second sound in anemic patients results from the lower blood viscosity, which reduces the damping forces that act upon the semilunar valve as it vibrates after closure. The reduced damping would allow augmented vibrations that result in an accentuated sound.

Anemia↗
PubMed1984

Measurement and theory of wheezing breath sounds.

We measured the time and frequency domain characteristics of breath sounds in seven asthmatic and three nonasthmatic wheezing patients. The power spectra of the wheezes were evaluated for frequency, amplitude, and timing of peaks of power and for the presence of an exponential decay of power with increasing frequency. Such decay is typical of normal vesicular breath sounds. Two patients who had the most severe asthma had no exponential decay pattern in their spectra. Other asthmatic patients had exponential patterns in some of their analyzed sound segments, with a range of slopes of the log power vs. log frequency curves from 5.7 to 17.3 dB/oct (normal range, 9.8-15.7 dB/oct). The nonasthmatic wheezing patients had normal exponential patterns in most of their analyzed sound segments. All patients had sharp peaks of power in many of the spectra of their expiratory and inspiratory lung sounds. The frequency range of the spectral peaks was 80-1,600 Hz, with some presenting constant frequency peaks throughout numerous inspiratory or expiratory sound segments recorded from one or more pickup locations. We compared the spectral shape, mode of appearance, and frequency range of wheezes with specific predictions of five theories of wheeze production: 1) turbulence-induced wall resonator, 2) turbulence-induced Helmholtz resonator, 3) acoustically stimulated vortex sound (whistle), 4) vortex-induced wall resonator, and 5) fluid dynamic flutter. We conclude that the predictions by 4 and 5 match the experimental observations better than the previously suggested mechanisms. Alterations in the exponential pattern are discussed in view of the mechanisms proposed as underlying the generation and transmission of normal lung sounds. The observed changes may reflect modified sound production in the airways or alterations in their attenuation when transmitted to the chest wall through the hyperinflated lung.

Adult↗
PubMed1998

Sensitivity to sound-source elevation in nontonotopic auditory cortex.

We have demonstrated that the spike patterns of auditory cortical neurons carry information about sound-source location in azimuth. The question arises as to whether those units integrate the multiple acoustical cues that signal the location of a sound source or whether they merely demonstrate sensitivity to a specific parameter that covaries with sound-source azimuth, such as interaural level difference. We addressed that issue by testing the sensitivity of cortical neurons to sound locations in the median vertical plane, where interaural difference cues are negligible. Auditory unit responses were recorded from 14 alpha-chloralose-anesthetized cats. We studied 113 units in the anterior ectosylvian auditory area and 82 units in auditory area A2. Broadband noise stimuli were presented in an anechoic room from 14 locations in the vertical midline in 20 degrees steps, from 60 degrees below the front horizon, up and over the head, to 20 degrees below the rear horizon, as well as from 18 locations in the horizontal plane. The spike counts of most units showed fairly broad elevation tuning. An artificial neural network was used to recognize spike patterns, which contain both the number and timing of spikes, and thereby estimate the locations of sound sources in elevation. For each unit, the median error of neural-network estimates was used as a measure of the network performance. For all 195 units, the average of the median errors was 46.4 +/- 9.1 degrees (mean +/- SD), compared with the expectation of 65 degrees based on chance performance. To address the question of whether sensitivity to sound pressure level (SPL) alone might account for the modest sensitivity to elevation of neurons, we measured SPLs from the cat's ear canal and compared the neural elevation sensitivity with the acoustical data. In many instances, the artificial neural network discriminated stimulus elevations even when the free-field sound produced identical SPLs in the ear canal. Conversely, two stimuli at the same elevation could produce the same network estimate of elevation, even when we varied sound-source SPL over a 20-dB range. There was a significant correlation between the accuracy of network performance in azimuth and in elevation. Most units that localized well in elevation also localized well in azimuth. Because the principal acoustic cues for localization in elevation differ from those for localization in azimuth, that positive correlation suggests that individual cortical neurons can integrate multiple cues for sound-source location.

Action Potentials↗
PubMed1976

Pseudoejection sound in hypertrophic subaortic stenosis: an echocardiographic correlative study.

Phonoechocardiographic studies were performed in 23 patients with hypertrophic subaortic stenosis. In ten patients a distinct systolic sound was recorded, usually along the lower left sternal border. In eight of these cases the sound was low or medium frequency. Unlike the ejection click of valvular aortic stenosis, the sound began 40-100 msec after the upstroke of the indirect carotid pulse and occurred close to the initial peak of the carotid pulse. This sound, termed pseudoejection sound, was associated with systolic anterior movement (SAM) of the anterior mitral leaflet on the echocardiogram. In all six patients studied with simultaneous phonoechocardiograms, the pseudoejection sound coincided with the sudden halting of SAM of the anterior mitral leaflet. Following provocative maneuvers the sound became louder, and its timing, as well as the sharp halting of SAM of the mitral leaflet, occurred earlier in systole. The pseudoejection sound probably results either from impact of the anterior mitral leaflet against the interventricular septum or more likely from deceleration of blood flow in the left ventricular outflow tract. The echo data support the association of the pseudoejection sound with significant left aventricular outflow obstruction,

Amyl Nitrite↗
PubMed2001

Auditory detection of simulated crackles in breath sounds.

BACKGROUND: Computerized analysis of breath sounds has relied on human auditory perception as the reference standard for identifying crackles. In this study, we tested the human audibility of crackles by superimposing artificial clicks on recorded breath sounds and having physicians listen to the recordings to see if they could identify the crackles. OBJECTIVES: To establish the audibility of simulated crackles introduced in breath sounds of different intensity, to study the effects of crackle characteristics on their audibility, and to investigate crackle detection within and between observers. METHODS: Fine, medium, and coarse crackles with large and small amplitude were synthesized by computer software. Waveform parameters were based on published characteristics of lung sound crackles. The amplitude for small crackles was defined as just above the threshold of audibility for simulated crackles inserted in sound recorded during breath hold. Simulated crackles were then superimposed on breath sounds recorded at 0 L/s (breath hold), 1 L/s, and 2 L/s airflow. Five physicians listened during playback on two separate occasions to determine if crackles could be heard and to calculate the interobserver and intraobserver variations. RESULTS: Failed detection of crackles was significantly more common in the following conditions: (1) background breath sounds had higher intensity (2 L/s airflow) compared to lower intensity (1 L/s), (2) crackle type was coarse or medium compared to fine, and (3) crackle amplitude was small compared to large. Both intraobserver and interobserver agreements were high (kappa > 0.6). RELEVANCE: The validation of automated techniques for crackle detection in lung sound analysis should not rely on auscultation as the only reference. Detection of crackles is facilitated when patients take slow, deep breaths that generate little breath sounds.

Auditory Perception↗
PubMed1984

The relationship between airflow and lung sound amplitude in normal subjects.

Few investigators have examined the relationship between airflow and lung sound amplitude; the available data are contradictory. I measured airflow at the mouth and compared the peak flow (Vmax) to mean and peak lung sound amplitude (mean AMP and peak AMP) at four sites on the chest wall (right and left anterior apices and posterior bases) in four healthy young adults. At each site, the sounds produced by 20 breaths at Vmax ranging between 1.5 and 4 L/s (Vvar) were measured by an automated technique. Ten breaths during nearly constant Vmax breathing (Vcon) also were measured at each site. The lung sound amplitudes at the four sites in each subject were grouped and compared to Vmax by linear regression analysis. The same sounds were also submitted to an automated V-correction procedure to evaluate its adequacy in automatically adjusting for the effect of variations in Vmax on lung sound amplitude. The data showed that lung sound amplitude (mean or peak) was linearly related to V in all subjects (r for mean AMP vs Vmax:0.77, 0.85, 0.69, 0.89; r for peak AMP vs Vmax:0.80, 0.83, 0.79, 0.88), p less than 1 X 10(-7) in all cases. The average mean AMP vs Vmax regression line slope was 0.42, and the average peak AMP vs Vmax regression line slope was 0.45. V-correction decreased the coefficient of variation of the Vvar sounds by 61 percent and flattened the average regression line slopes to 0.128. For the Vcon series, V-correction diminished the coefficient of variation from 12.2 to 10.0 percent. The relationship between lung sound amplitude and airflow appears to be substantially linear and this relationship can be used to adjust effectively for variations in airflow.

Adult↗
PubMedDate not supplied

[Application of the lateralization sound test in elderly individuals].

BACKGROUND: The ability to determine the direction of a sound source is based on the fact that sounds reach both cars at different times, phase, intensity and/or frequency. The perception of a sound source favors speech intelligibility in noisy environments. AIM: To identify the minimum time of interaural delay--produces lateralization to the car which the stimulus reached first--through ascendant and descendent techniques, using the Sound Lateralization Test in elderly individuals with normal hearing thresholds in the frequencies which are most important for speech comprehension. METHOD: The Lateralization Test was used in 30 individuals with ages above 60 years, who presented hearing thresholds up to 25 dBHL in 500, 1000 and 2000 Hz and with no air-bone gap. RESULTS: Mean times of interaural delay in sound lateralization were: a) ascending technique: 125.56 sec. (female) and 83.61 sec. (male); b) descending technique: 95.06 sec. (female) and 61.68 sec (male). CONCLUSION: There is no difference between the mean time of interaural delay in sound lateralization obtained with the ascending or descending technique regarding the variable initial tested ear (right or left ear); the mean time of interaural delay in sound lateralization is smaller in males, when considering both ascendant and descendent techniques; the mean time of interaural delay in sound lateralization obtained with the descendent technique is smaller than that obtained with the ascendant technique; individuals who present hearing losses beginning at 3000 Hz have smaller mean times of interaural delay in sound lateralization than normal hearing individuals in both techniques.

Aged↗
PubMedDate not supplied

Elevated sound levels within a busy NICU.

PURPOSE: Elevated sound levels in the NICU may contribute to undesirable physiologic and behavioral effects in preterm infants. This study describes sound levels in a busy NICU in the southeastern U.S. and compares the findings with recommended NICU noise level standards. DESIGN: NICU sound levels were recorded continuously at nine different locations within the NICU. Hourly measurements of loudness equivalent (Leq) sound level, sound level exceeded 10 percent of the time (L10), and maximum sound level (Lmax) were determined. SAMPLE: Sound levels were sampled from nine different locations within the NICU. MAIN OUTCOME VARIABLE: Sound levels are described using the hourly, A-weighted Leq, L10, and Lmax. RESULTS: The overall average hourly Leq (M = 60.44 dB, range = 55-68 dB), L10 (M = 59.26 dB, range = 55-66 dB), and Lmax (M = 78.39, range = 69-93 dB) were often above the recommended sound levels (hourly Leq <50 dB, L10 <55 dB, and 1-second Lmax <70 dB). In addition, certain times of day, such as 6-7 AM and 10 AM-12 noon, were noisier than other times of day.

Clinical Nursing Research↗
PubMed1979

The control of responding by sounds: unusual effect of reinforcement.

Naive rats were trained to respond on one lever in the presence of noise bursts from one speaker and on a second lever in the presence of noise bursts from a second speaker. The speakers were mounted behind the levers. When responding on the lever adjacent to the sounding speaker was reinforced, control developed within fewer than five trials. When responding on the nonadjacent lever was selectively reinforced, responding on the lever adjacent to the sounding speaker increased in probability for several sessions. Naive rats were trained to respond on the nonadjacent lever following preexposure to the sound. Responding on the lever adjacent to the sounding speaker increased in probability, showing that novelty was not responsible for the effect. Naive rats were run on automaintenance procedures in which there was no explicit pairing of sound and magazine operation, 100% pairing of sound and magazine operation, or magazine operation following 40% of sound presentations. None of the rats acquired the response of approaching and sniffing the sounding speaker, indicating that sound-magazine pairing was not responsible for the effect.

Acoustic Stimulation↗
PubMed2004

How to select stimuli for environmental sound research and where to find them.

A major methodological challenge in environmental sound research is to select appropriate stimuli. When an experiment involves a large number of sound sources, making custom recordings orproducing sounds live is frequently impractical or, for certain sounds, impossible. Existing databases of environmental sound recordings provide a researcher with a useful alternative. However, finding and selecting suitable sounds in such databases can be difficult because of the great variety of sounds present, poor documentation, questionable recording quality, and required purchasing costs. This article describes a number of practical issues to consider during the stimulus selection process, offers a preliminary compilation of existing resources for obtaining environmental sound recordings, provides some normative perceptual data that can be used as a reference for selecting stimuli and evaluating performance, and lists required characteristics and structural aspects of a research-oriented environmental sound database.

Adolescent↗