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At least 1,513 records · Page 84Linked to original sources
PubMed2000

Sound transmission between 50 and 600 Hz in excised pig lungs filled with air and helium.

This study measured transit time (TT) and attenuation of sound transmitted through six pairs of excised pig lungs. Single-frequency sounds (50-600 Hz) were applied to the tracheal lumen, and the transmitted signals were monitored on the tracheal and lung surface using microphones. The effect of varying intrapulmonary pressure (Pip) between 5 and 25 cmH(2)O on TT and sound attenuation was studied using both air and helium (He) to inflate the lungs. From 50 to approximately 200 Hz, TT decreased from 4.5 ms at 50 Hz to 1 ms at 200 Hz (at 25 cmH(2)O). Between approximately 200 and 600 Hz, TT was relatively constant (1.1 ms at upper and 1.5 ms at lower sites). Gas density had very little effect on TT (air-to-He ratio of approximately 1.2 at upper sites and approximately 1 at lower sites at 25 cmH(2)O). Pip had marked effects (depending on gas and site) on TT between 50 and 200 Hz but no effect at higher frequencies. Attenuation was frequency dependent between 50 and 600 Hz, varying between -10 and -35 dB with air and -2 and -28 dB with He. Pip also had strong influence on attenuation, with a maximum sensitivity of 1.14 (air) and 0.64 dB/cmH(2)O (He) at 200 Hz. At 25 cmH(2)O and 200 Hz, attenuation with air was about three times higher than with He. This suggests that sound transmission through lungs may not be dominated by parenchyma but by the airways. The linear relationship between increasing Pip and increasing attenuation, which was found to be between 50 and approximately 100 Hz, was inverted above approximately 100 Hz. We suggest that this change is due to the transition of the parenchymal model from open to closed cell. These results indicate that acoustic propagation characteristics are a function of the density of the transmission media and, hence, may be used to locate collapsed lung tissue noninvasively.

Acoustics↗
PubMed2004

An upper airway resonator model of high-frequency inspiratory sounds in children with sleep-disordered breathing.

The goal of this study was to determine how high-frequency inspiratory sounds (HFIS) are generated by sleeping children with obstructive sleep-disordered breathing (OSDB). We hypothesized that HFIS are generated when a high-velocity jet of air, generated by a narrowed upper airway, induces the upper airway to act as a resonating chamber. We tested two predictions of this hypothesis: 1) the upper airway is narrowed in children who make HFIS and 2) the length of the upper airway, calculated from HFIS harmonic intervals, is similar to that calculated from magnetic resonance imaging (MRI) scans. The study was conducted in the setting of a sleep laboratory. Participants included 29 children between 6 and 12 yr of age with adenotonsillar hypertrophy suspected of having OSDB. Minimum cross-sectional airway area and airway long dimensions (lips to larynx or soft palate) were measured in awake children with MRIs. Later that night, sound was recorded with a microphone suspended above their bed while the children underwent polysomnography. Sounds were later analyzed with fast Fourier transforms. We found that sleeping children who generated HFIS had significantly narrower upper airways compared with children who did not make HFIS [minimum airway area 20.5 +/- 4.4 vs. 70.9 +/- 22.5 mm(2) (mean +/- SE), respectively; P = 0.02]. There was a significant inverse correlation between the log(10) of the narrowest airway area and the number of HFIS recorded per hour (r(2) = 0.55, P < 0.00001). The harmonics characteristics of HFIS predicted that they were generated by sound resonating in chamber whose length was 12.0 +/- 0.9 cm, which is similar to the MRI measured distance from the lips to the larynx of 12.8 +/- 0.4 cm. In conclusion, these data suggest that children generate HFIS when 1) they have a narrowed upper airway and 2) their upper airway acts as a resonating chamber.

Child↗
PubMed2005

Cortical representations of temporal structure in sound.

Pitch and spatial width are two sound attributes that can be coded by temporal acoustic structure. In this study, periodicity pitch was created by temporal iteration in a regular-interval noise, whereas spatial width was determined by the degree of interaural correlation. Previous results suggest that nonprimary auditory cortex, particularly lateral Heschl's gyrus (HG), plays an important role in the analysis of both acoustic properties. It has been argued that this role might reflect a common computational process. One proposed candidate is that of integrating the temporal pattern information across frequency channels. This paper reports the results of a systematic test for whether different classes of temporal structure do indeed engage a common neural architecture in the human auditory cortex by presenting both classes of sound stimuli to a single group of listeners. Activations related to the pitch and spatial width of the sound were partly co-localized in two distinct cortical regions: close to lateral HG and in planum temporale (PT). Lateral HG was more responsive to temporal pitch than to spatial width. This difference plus the variability across listeners for spatial width dispute the claim that the activity in lateral HG reflects a common neural computational step that encodes the temporal patterns associated with pitch and spatial width. Rather, the activity patterns are consistent with a role for lateral HG in perceptual analysis as opposed to temporal acoustic structure. In PT, the superadditive relationship between pitch and spatial width is also consistent with the concept that the auditory cortex plays an important role in integrating different classes of sound information to form auditory objects.

Acoustic Stimulation↗
PubMed2006

Sound localization by barn owls in a simulated echoic environment.

We examined the accuracy and precision with which the barn owl (Tyto alba) turns its head toward sound sources under conditions that evoke the precedence effect (PE) in humans. Stimuli consisted of 25-ms noise bursts emitted from two sources, separated horizontally by 40 degrees, and temporally by 3-50 ms. At delays from 3 to 10 ms, head turns were always directed at the leading source, and were nearly as accurate and precise as turns toward single sources, indicating that the leading source dominates perception. This lead dominance is particularly remarkable, first, because on some trials, the lagging source was significantly higher in amplitude than the lead, arising from the directionality of the owl's ears, and second, because the temporal overlap of the two sounds can degrade the binaural cues with which the owl localizes sounds. With increasing delays, the influence of the lagging source became apparent as the head saccades became increasingly biased toward the lagging source. Furthermore, on some of the trials at delays > or = 20 ms, the owl turned its head, first, in the direction of one source, and then the other, suggesting that it was able to resolve two separately localizable sources. At all delays <50 ms, response latencies were longer for paired sources than for single sources. With the possible exception of response latency, these findings demonstrate that the owl exhibits precedence phenomena in sound localization similar to those in humans and cats, and provide a basis for comparison with neurophysiological data.

Acoustic Stimulation↗
PubMed2005

Processing of modulated sounds in the zebra finch auditory midbrain: responses to noise, frequency sweeps, and sinusoidal amplitude modulations.

The avian auditory midbrain nucleus, the mesencephalicus lateralis, dorsalis (MLd), is the first auditory processing stage in which multiple parallel inputs converge, and it provides the input to the auditory thalamus. We studied the responses of single MLd neurons to four types of modulated sounds: 1) white noise; 2) band-limited noise; 3) frequency modulated (FM) sweeps, and 4) sinusoidally amplitude-modulated tones (SAM) in adult male zebra finches. Responses were compared with the responses of the same neurons to pure tones in terms of temporal response patterns, thresholds, characteristic frequencies, frequency tuning bandwidths, tuning sharpness, and spike rate/intensity relationships. Most neurons responded well to noise. More than one-half of the neurons responded selectively to particular portions of the noise, suggesting that, unlike forebrain neurons, many MLd neurons can encode specific acoustic components of highly modulated sounds such as noise. Selectivity for FM sweep direction was found in only 13% of cells that responded to sweeps. Those cells also showed asymmetric tuning curves, suggesting that asymmetric inhibition plays a role in FM directional selectivity. Responses to SAM showed that MLd neurons code temporal modulation rates using both spike rate and synchronization. Nearly all cells showed low-pass or band-pass filtering properties for SAM. Best modulation frequencies matched the temporal modulations in zebra finch song. Results suggest that auditory midbrain neurons are well suited for encoding a wide range of complex sounds with a high degree of temporal accuracy rather than selectively responding to only some sounds.

Acoustic Stimulation↗
PubMed1985

Effects of medial geniculate lesions on sound localization by the rat.

Rats with bilateral lesions of the medial geniculate body were tested on a two-choice sound-localization task that required a directional response to a distant sound source. Stimuli included both broadband and filtered noise bursts presented singly or in repetitive trains. Separate tests were conducted with loudspeakers 180 and 60 degrees apart, centered around 0 degree azimuth. With complete bilateral destruction of the medial geniculate, rats could localize both trains and single bursts of noise and were capable of high levels of performance even at small angles of speaker separation. Some evidence of impaired performance was noted with high-frequency noise bursts, but generally the deficits were not severe. Animals with lesions that extended caudally into the brachium of the inferior colliculus and lateral tegmentum were severely impaired in their ability to localize sounds even at large angles of speaker separation. Three of the four animals in this group were incapable of localizing single bursts even with loudspeakers separated by 180 degrees, and the fourth was unable to perform above chance at 60 degrees. The effects of medial geniculate lesions were very similar to those reported previously for rats with lesions of the auditory cortex, but contrasted with reports of severe impairments in sound localization following damage to the auditory cortex in other mammalian species.

Animals↗
PubMed1993

Sound direction influences the frequency-tuning characteristics of neurons in the frog inferior colliculus.

1. We investigated the influence of sound direction on the frequency-tuning characteristics of neurons in the frog inferior colliculus, the torus semicircularis. For each neuron, we used tone bursts to determine the frequency-threshold curves (FTCs) for three to seven loudspeaker azimuths. The loudspeaker was mounted on a rotatable arc and could be swung through the frontal field between positions opposite the ear that was contralateral to the recording site (C90 degrees) and the ear that was ipsilateral to the recording site (I90 degrees). 2. Frequency-tuning data from 83 units showed that the characteristic frequency (CF) shift through a 180 degrees change in loudspeaker azimuth was typically small, i.e., 85% of neurons showed maximum absolute changes in CF that were < 0.4 octaves. Paired comparisons of CFs for each neuron when the loudspeaker was located at C90 degrees, and the frontal midline position (0 degree) revealed no significant differences (P > 0.2) between azimuths. The magnitude of CF shift between different sound directions showed no systematic pattern. 3. In contrast to the CF, midbrain neurons showed distinct changes in the minimum threshold (MT) at CF across 180 degrees of azimuth. The maximum absolute change in MT ranged from 0 to 38 dB, with a mean of 10.9 dB. A pair-wise comparison of MTs, for each neuron, derived with the speakers at C90 degrees, 0 degree, and I90 degrees, revealed that the MT typically increased when the loudspeaker was rotated toward I90 degrees (P < 0.0001). 4. The most prominent effect of rotating the loudspeaker from C90 degrees to I90 degrees was a narrowing of the FTC. Sharpness of tuning in simple V-shaped FTCs was most directly shown by changes in the Q factors at 10, 20, and 30 dB above MT as a function of sound direction. A pair-wise comparison for individual neurons showed that all Q factors were significantly larger (sharper tuning) for I90 degrees compared with C90 degrees (P < 0.02). The Q20dB values were also significantly larger for I90 degrees compared with 0 degree (P < 0.05). For the majority of units, the maximum Q10dB and Q20 dB values were displayed when the loudspeaker was positioned at I90 degrees; however, the maximum Q30dB was distributed nearly equally for the three azimuths. These results suggest that a change in sound direction has the most robust effect on tuning properties of the FTCs nearest the MT.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1994

Processing of frequency-modulated sounds in the cat's anterior auditory field.

1. Single-neuron activity was recorded from the anterior auditory field (AAF) in the cortex of gas-anesthetized cats. 2. Tone bursts and broad-band complex sounds were used for auditory stimulation. Responses to frequency-modulated (FM) sounds, in particular, were studied systematically. 3. Linear FM sweeps were centered around the best frequency (BF) of a neuron and had an excursion large enough to cover its whole frequency tuning range. Rate and direction of change of the FM sweeps were varied. 4. In 69% of the FM responses, a peak was found at an instantaneous frequency that corresponded to the BF in the pure-tone response. Thirty-three percent of the units had multiple maxima in their FM response. These secondary maxima were not always reflected in the pure-tone response of the same neurons. 5. The vast majority of AAF neurons showed one of two types of selectivity for FM rate. Depending on the criterion, almost half of the cells (46%) preferred fast changes of > 200 Hz/ms (high-pass) in both FM directions. Forty-eight percent of all neurons showed band-pass behavior with a clear preference in the middle range of FM rates in one or both directions. Low-pass or all-pass neurons made up only a small proportion (4 and 1%, respectively) of AAF neurons. 6. When both directions of an FM sweep (low-to-high and high-to-low-frequency) were tested, 66% of the neurons clearly were selective for one direction. This selectivity was not present necessarily at the preferred FM rate. In general, FM direction selectivity was most pronounced at slower FM rates. 7. The selectivity of AAF neurons for the rate and direction of FM sounds makes these neurons suitable for the detection and analysis of communication sounds, which often contain FM components with a particular sweep rate and direction.

Animals↗
PubMed2001

Spatial attention modulates sound localization in barn owls.

Attentional influence on sound-localization behavior of barn owls was investigated in a cross-modal spatial cuing paradigm. After being cued to the most probable target side with a visual cuing stimulus, owls localized upcoming auditory target stimuli with a head turn toward the position of the sound source. In 80% of the trials, cuing stimuli pointed toward the side of the upcoming target stimulus (valid configuration), and in 20% they pointed toward the opposite side (invalid configuration). We found that owls initiated the head turns by a mean of 37.4 ms earlier in valid trials, i.e., mean response latencies of head turns were reduced by 16% after a valid cuing stimulus. Thus auditory stimuli appearing at the cued side were processed faster than stimuli appearing at the uncued side, indicating the influence of a spatial-selective attention mechanism. Turning angles were not different when owls turned their head toward a cued or an uncued location. Other types of attention influencing sound localization, e.g., a reduction of response latency as a function of the duration of cue-target delay, could not be observed. This study is the first attempt to investigate attentional influences on sound localization in an animal model.

Acoustic Stimulation↗
PubMedDate not supplied

A sound spectrogram analysis of children's crying after painful stimuli during the first year of life.

In a prospective study we tested the hypothesis that a cry from an infant can be used as part of an instrument to measure pain. Ten healthy newly born infants were subjected to painful stimuli on four occasions during their first year of life. The sound of the crying was analysed with regard to duration. With the help of a sound spectrogram, the fundamental frequencies of the first five crying sounds were analysed. The number of crying sounds decreased with age. There was a considerable difference between the 10 children, and also between the different pricking occasions for the respective children. We conclude that if crying is to be used as part of an instrument for measuring pain, the child's age has to be taken into account.

Age Factors↗
PubMed1995

Left-right discrimination of sound onset by the Mauthner system.

We present a neural model for how the Mauthner system could compute the direction of a transient sound stimulus originating on either the left or right side of a fish. This computation results in an initial orientation of an escape response away from the side of the stimulus. Our idea is based on the phase model of underwater sound localization by fishes. If the phase model is applicable to the Mauthner system, then the problem of sound localization can be reduced to a logical operator, the EXCLUSIVE-NOR (or XNOR). We show how this can be solved by the Mauthner system using afferents that convey separate inputs of sound pressure transduced by the swimbladder (rarefaction and compression) and particle displacement (left and right) from the inner ear. In our model, both pressure components are responsible for bringing the Mauthner cell to threshold. Mauthner firing is gated by the inhibitory PHP neurons receiving specific combinations of pressure and displacement that implement the XNOR logic. We refer to this as the XNOR model. This model is experimentally verifiable and makes specific predictions about the expected acoustic response characteristics of the Mauthner and PHP neurons. Our model places a component of PHP function into a new neuroethological context and may provide insights into the central neurophysiological mechanisms of directional hearing in fishes. In particular, we show how the XNOR model can be applied to predict the activity of diverse neural elements involved in acoustic localization by fishes.

Animals↗
PubMed1990

Presystolic tricuspid valve closure: an alternative mechanism of diastolic sound genesis.

We describe a previously unrecognised cause of an added diastolic heart sound. The patient had first-degree heart block and diastolic tricuspid regurgitation, leading to presystolic closure of the tricuspid valve and the production of a loud diastolic sound. Unlike previously described mechanisms for diastolic sounds, this sound was generated by the sudden acceleration of retrograde AV flow in late diastole.

Aged↗
PubMed1975

Echocardiographic observations on the mechanism of production of the second heart sound.

This investigation was designed to determine the echocardiographic correlates of the aortic and pulmonary components of the second heart sound. Simultaneous recordings of the ECG, phonocardiogram, carotid pulse tracing and the echocardiogram of the aortic valve were made in 54 patients. The tracings were recorded at a paper speed of 100 mm/sec, with 20 msec time lines. Aortic valve closure (AVC) on the echocardiogram occurred before the onset of the aortic component of the second heart sound (A2) in all but two patients. The mean AVC-to-A2 interval was 12 msec with a range of 5 to 25 msec. Simultaneous recordings of the pulmonary valve echocardiogram, ECG, phonocardiogram and carotid pulse tracing were made in 14 patients. Pulmonary valve closure (PVC) on the echocardiogram preceded the pulmonary component of the second sound (P2) in all patients. The mean PVC-2 interval was 60 msec with a range of 30 to 75 msec. We conclude that aortic valve closure and pulmonary valve closure are not directly responsible for the genesis of the second heart sound (S2). These observations are consonant with the theory that S2 is caused by deceleration of columns of blood resulting from semilunar valve closure, throwing the cardiohemic system into vibration.

Adolescent↗
PubMed1996

Lung sounds during allergen-induced asthmatic responses in patients with asthma.

We postulated that the distinct pathophysiologic mechanisms of airway narrowing during the early (EAR) and the late (LAR) asthmatic responses to inhaled allergens are reflected by the generation or transmission of lung sounds in asthma. Therefore, we measured FEV1 and recorded lung sounds in eight mildly asthmatic subjects before a standardized allergen challenge (PRE), during the EAR, during the recovery phase at 2 h (MID), during the LAR at 7 h, and after inhalation of a bronchodilator (POST). The recordings were made during flow- and volume-standardized quiet breathing, and during maximal forced breathing maneuvers. Airflow-dependent power spectra were analyzed for lung sound intensity (LSI), quartile power points (Q25, Q50, Q75), and extent of wheezing (W). These sound characteristics were compared among the various stages of the challenge in the presence (EAR, LAR) and absence (PRE, MID, POST) of acute airway obstruction using ANOVA. LSI, Q25 - Q75, and W were all elevated during airway obstruction. When matched for percent fall in FEV1, during the EAR and the LAR (mean +/- SD: 26.7 +/- 4.0, and 28.9 +/- 5.7, respectively; p = 0.385), the increase in Q25, and Q50 with airflow during quiet expiration, as well as the extent of wheezing, were higher during the LAR than during the EAR (p < or = 0.042 and p < or = 0.012, respectively). At similar levels of FEV1 (p > or = 0.156), LSI on expiration was higher at POST than at PRE or MID (p < or = 0.067), whereas Q25 (p < or = 0.047) and Q50 (p < or = 0.064) were lower at POST than at PRE. During forced expiration W was higher at MID and POST than at PRE (p < or = 0.014). We conclude that LSI, frequency content, and the extent of wheezing vary during the subsequent stages of allergen-induced bronchoconstriction in asthma despite matched values of FEV1. This suggests that airflow-standardized phonopneumography is a sensitive method for detecting differences in the pathophysiology of airway narrowing in asthma.

Acoustics↗
PubMed2000

The relationship between normal lung sounds, age, and gender.

Auscultation is one of the most important noninvasive and feasible methods for the detection of lung diseases. Systematic changes in breathing sounds with increasing age are of diagnostic importance. To investigate these changes, we recorded lung sounds taken from four locations in the posterior thorax of 162 subjects, together with airflow. The data were analyzed according to age, sex, and smoking habit. In order to describe the power spectrum of the lung sounds, we calculated mean and median frequency, frequency with the highest power, and a ratio (Q) of relative power of the two frequency bands of 330 to 600 Hz and 60 to 330 Hz. Linear regression analysis was used as a measurement of age-dependence of these variables. Significant differences in Q were found in men versus women (p < 0.05), but not in smokers versus nonsmokers. Within the groups, a small but significant correlation existed between Q and age (r(2) </= 0.1, p < 0.05). For both men and women, a slight increase of the relative power in the frequency band of 330 to 600 Hz was recorded with increasing age. However, on the basis of large individual variations, these small changes (DeltaQ approximately 5%, SD(Q) >/= +/- 5%) have no clinical significance and need not to be considered in the automatic detection of lung diseases by analyzing lung sounds.

Adult↗
PubMed1988

Airflow and normal lung sounds.

The relationship between total air flow and normal breath sounds recorded at 2 sites on the chest was investigated. Sounds were measured during rhythmic breathing, during flow rate tracking, and during flow rate tracking against an external resistance by subjects seated and in the left lateral decubitus position. The sound amplitude during inspiration varied directly with the square of the air flow at the mouth. Changes in subject position and breathing pattern altered the gain between the square of the flow and the sound amplitude but not the functional relationship.

Adult↗
PubMed1980

Determination of the site of production of respiratory sounds by subtraction phonopneumography.

The site of origin of the vesicular lung sound has long been in question. A technique (subtraction phonopneumography) is described here for determining the relative distance of a sound source from the chest wall. This technique involves the simultaneous recording of lung sounds from two different sites on the chest wall, phase inversion of one of the signals, and then mixing the signals in a summing amplifier. The degree of cancellation that results is inversely proportional to the number of sources and the degree to which each source is detected by both microphones simultaneously. A study of six normal subjects revealed little or no cancellation of inspiratory vesicular sounds with microphones separated by 10 cm. During expiration, cancellation did occur at distances well beyond 10 cm and was detectable over several homologous segments of opposite lungs. This finding is consistent with an intrapulmonic and probably intralobar source for the inspiratory component and an upper airway source for at least some of the expiratory component.

Auscultation↗
PubMed1980

Use of laryngeal sound recordings to monitor apnea.

Laryngeal sounds are produced by air flow across the glottis. We found that apnea could be identified by the cessation of laryngeal sounds during continuous monitoring. We recorded laryngeal sounds using a microphone coupled to a stethoscope head taped to the subject's lateral neck. This signal was conditioned using a commercially available amplifier and displayed on a time-based recorder. Laryngeal sound monitoring of apnea could be useful in sleep studies.

Adult↗