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At least 1,333 records · Page 74Linked to original sources
PubMed2004

Spirometry and forced oscillometry assisted optimal frequency band determination for the computerized analysis of tracheal lung sounds in asthma.

We analysed respiration sounds of individual asthmatic patients, in the scope of the development of a method for computerized recognition of the degree of airway obstruction. Respiration sounds were recorded during laboratory sessions of histamine-provoked airway obstruction. We applied an interpolation technique using supervised artificial neural networks to investigate the optimal frequency band required for studying tracheal asthmatic lung sounds. The optimal band was found to be 100-2300 Hz. The forced expiratory volume in 1 s (FEV1) and the respiratory resistance parameter Rrs(4) were used to describe the degree of airway obstruction that is associated with the lung sounds. By comparing the results obtained with the two parameters, we found that for parametrization of the associated degree of airway obstruction respiratory resistance measurements are preferable over forced expiratory volume measurements.

Adult↗
PubMed2005

Geographical variation in sound production in the anemonefish Amphiprion akallopisos.

Because of pelagic-larval dispersal, coral-reef fishes are distributed widely with minimal genetic differentiation between populations. Amphiprion akallopisos, a clownfish that uses sound production to defend its anemone territory, has a wide but disjunct distribution in the Indian Ocean. We compared sounds produced by these fishes from populations in Madagascar and Indonesia, a distance of 6500 km. Differentiation of agonistic calls into distinct types indicates a complexity not previously recorded in fishes' acoustic communication. Moreover, various acoustic parameters, including peak frequency, pulse duration, number of peaks per pulse, differed between the two populations. The geographic comparison is the first to demonstrate 'dialects' in a marine fish species, and these differences in sound parameters suggest genetic divergence between these two populations. These results highlight the possible approach for investigating the role of sounds in fish behaviour in reproductive divergence and speciation.

Agonistic Behavior↗
PubMed2006

Effects of diameter, length, and circuit pressure on sound conductance through endotracheal tubes.

We evaluated the acoustic frequency response of endotracheal tubes (ETs) to assess their effect on respiratory system sound transmission studies. White noise 150-3300 Hz was introduced into 4.0-, 6.0-, and 8.0-mm ETs and recorded at their proximal and distal ends. Four tubes of each size were studied at their original and normalized lengths, in straight and bent configurations, and at circuit pressures from 0 to 20 cmH2O. The characteristics of the sound transmission were compared using an analysis of variance for repeated measures. The average transmission amplitude varied directly with tube diameter. The position of peaks and troughs on the amplitude frequency distribution depended on tube length but not on tube diameter. The angle of the phase-frequency plot correlated well with the length of the tube and was independent of its diameter. A 90 degrees bend in the tube had no effect on its sound transmission. Increasing the circuit pressure above ambient modified the frequency response only if volume changes occurred in the test lung. When used to conduct sound into the respiratory system an ET affects the incident signal predictably depending on its length and diameter but not on its curvature or circuit pressure.

Animals↗
PubMed2004

Enhanced sound localization.

A new approach to sound localization, known as enhanced sound localization, is introduced, offering two major benefits over state-of-the-art algorithms. First, higher localization accuracy can be achieved compared to existing methods. Second, an estimate of the source orientation is obtained jointly, as a consequence of the proposed sound localization technique. The orientation estimates and improved localizations are a result of explicitly modeling the various factors that affect a microphone's level of access to different spatial positions and orientations in an acoustic environment. Three primary factors are accounted for, namely the source directivity, microphone directivity, and source-microphone distances. Using this model of the acoustic environment, several different enhanced sound localization algorithms are derived. Experiments are carried out in a real environment whose reverberation time is 0.1 seconds, with the average microphone SNR ranging between 10-20 dB. Using a 24-element microphone array, a weighted version of the SRP-PHAT algorithm is found to give an average localization error of 13.7 cm with 3.7% anomalies, compared to 14.7 cm and 7.8% anomalies with the standard SRP-PHAT technique.

Algorithms↗
PubMed2006

A probabilistic model for binaural sound localization.

This paper proposes a biologically inspired and technically implemented sound localization system to robustly estimate the position of a sound source in the frontal azimuthal half-plane. For localization, binaural cues are extracted using cochleagrams generated by a cochlear model that serve as input to the system. The basic idea of the model is to separately measure interaural time differences and interaural level differences for a number of frequencies and process these measurements as a whole. This leads to two-dimensional frequency versus time-delay representations of binaural cues, so-called activity maps. A probabilistic evaluation is presented to estimate the position of a sound source over time based on these activity maps. Learned reference maps for different azimuthal positions are integrated into the computation to gain time-dependent discrete conditional probabilities. At every timestep these probabilities are combined over frequencies and binaural cues to estimate the sound source position. In addition, they are propagated over time to improve position estimation. This leads to a system that is able to localize audible signals, for example human speech signals, even in reverberating environments.

Artificial Intelligence↗
PubMed2000

Localization of multiple sound sources with two microphones.

This paper presents a two-microphone technique for localization of multiple sound sources. Its fundamental structure is adopted from a binaural signal-processing scheme employed in biological systems for the localization of sources using interaural time differences (ITD). The two input signals are transformed to the frequency domain and analyzed for coincidences along left/right-channel delay-line pairs. The coincidence information is enhanced by a nonlinear operation followed by a temporal integration. The azimuths of the sound sources are estimated by integrating the coincidence locations across the broadband of frequencies in speech signals (the "direct" method). Further improvement is achieved by using a novel "stencil" filter pattern recognition procedure. This includes coincidences due to phase delays of greater than 2pi, which are generally regarded as ambiguous information. It is demonstrated that the stencil method can greatly enhance localization of lateral sources over the direct method. Also discussed and analyzed are two limitations involved in both methods, namely missed and artifactual sound sources. Anechoic chamber tests as well as computer simulation experiments showed that the signal-processing system generally worked well in detecting the spatial azimuths of four or six simultaneously competing sound sources.

Adult↗
PubMed2000

Localization of brief sounds: effects of level and background noise.

Listeners show systematic errors in vertical-plane localization of wide-band sounds when tested with brief-duration stimuli at high intensities, but long-duration sounds at any comfortable level do not produce such errors. Improvements in high-level sound localization associated with increased stimulus duration might result from temporal integration or from adaptation that might allow reliable processing of later portions of the stimulus. Free-field localization judgments were obtained for clicks and for 3- and 100-ms noise bursts presented at sensation levels from 30 to 55 dB. For the brief (clicks and 3-ms) stimuli, listeners showed compression of elevation judgments and increased rates and unusual patterns of front/back confusion at sensation levels higher than 40-45 dB. At lower sensation levels, brief sounds were localized accurately. The localization task was repeated using 3-ms noise burst targets in a background of spatially diffuse, wide-band noise intended to pre-adapt the system prior to the target onset. For high-level targets, the addition of background noise afforded mild release from the elevation compression effect. Finally, a train of identical, high-level, 3-ms bursts was found to be localized more accurately than a single burst. These results support the adaptation hypothesis.

Adolescent↗
PubMed2004

Contrasting monaural and interaural spectral cues for human sound localization.

A human psychoacoustical experiment is described that investigates the role of the monaural and interaural spectral cues in human sound localization. In particular, it focuses on the relative contribution of the monaural versus the interaural spectral cues towards resolving directions within a cone of confusion (i.e., directions with similar interaural time and level difference cues) in the auditory localization process. Broadband stimuli were presented in virtual space from 76 roughly equidistant locations around the listener. In the experimental conditions, a "false" flat spectrum was presented at the left eardrum. The sound spectrum at the right eardrum was then adjusted so that either the true right monaural spectrum or the true interaural spectrum was preserved. In both cases, the overall interaural time difference and overall interaural level difference were maintained at their natural values. With these virtual sound stimuli, the sound localization performance of four human subjects was examined. The localization performance results indicate that neither the preserved interaural spectral difference cue nor the preserved right monaural spectral cue was sufficient to maintain accurate elevation judgments in the presence of a flat monaural spectrum at the left eardrum. An explanation for the localization results is given in terms of the relative spectral information available for resolving directions within a cone of confusion.

Acoustic Stimulation↗
PubMed2006

Lefties get it "right" when hearing tool sounds.

Our ability to manipulate and understand the use of a wide range of tools is a feature that sets humans apart from other animals. In right-handers, we previously reported that hearing hand-manipulated tool sounds preferentially activates a left hemisphere network of motor-related brain regions hypothesized to be related to handedness. Using functional magnetic resonance imaging, we compared cortical activation in strongly right-handed versus left-handed listeners categorizing tool sounds relative to animal vocalizations. Here we show that tool sounds preferentially evoke activity predominantly in the hemisphere "opposite" the dominant hand, in specific high-level motor-related and multisensory cortical regions, as determined by a separate task involving pantomiming tool-use gestures. This organization presumably reflects the idea that we typically learn the "meaning" of tool sounds in the context of using them with our dominant hand, such that the networks underlying motor imagery or action schemas may be recruited to facilitate recognition.

Acoustic Stimulation↗
PubMed1982

Sound output of electronic laryngeal prostheses at room and body temperature.

An electronic laryngeal prosthesis, fully-implantable in the neck, is a desirable source of artificial voice. Emitted sound energy in a frequency range suitable for adult males and females must be of the correct period and intensity and rich in powerful harmonics. Any such device places severe demands on a bioencapsulant used to enclose the transducer. Location of the devices within the central neck demands a prosthesis-coating combination capable of passing sound energy at central body temperature. This study reports on four identical prostheses, coated with a polyvinylidene chloride, a copolyether polyurethane, a semi-rigid epoxy, or uncoated. Units were tested at room (72 degrees F) and body (100 degrees F) temperature in a sound-isolated chamber. Results indicated that performance of the uncoated unit was altered due to temperature effects. The presence of the polymer encapsulants did not have any differential effect on sound spectrum due to temperature differences.

Biocompatible Materials↗
PubMed2003

The influence of the acoustic context on vertical sound localization in the median plane.

The influence of background sounds (frames) on vertical localization of single sound sources (targets) was examined in four experiments. Loudspeakers (five targets and four frames) were positioned in the median plane, ranging from +30 degrees to -30 degrees above and below the subject's ear level. The subjects determined the vertical position of the targets by either verbal judgments or manual pointing. Frame and target sounds were presented concurrently or successively with a 1-sec interval; both consisted of (1) 300-Hz square waves, (2) noise, or (3) targets of noise and frames of 300-Hz square waves. Particularly in the second condition, the subjects consistently shifted the apparent target positions away from the frame locations. This contrast effect persisted even 1 sec after the offset of the frames. No effect was found with different waveforms for the frame and the target. Results are related to recent findings indicating a similar effect in the azimuthal dimension. Possibly the effect is based on a mechanism in which the auditory system adapts to recently heard sound source positions.

Acoustic Stimulation↗
PubMed1996

A simulated "cocktail party" with up to three sound sources.

Listeners identified spoken words, letters, and numbers and the spatial location of these utterances in three listening conditions as a function of the number of simultaneously presented utterances. The three listening conditions were a normal listening condition, in which the sounds were presented over seven possible loudspeakers to a listener seated in a sound-deadened listening room; a one-headphone listening condition, in which a single microphone that was placed in the listening room delivered the sounds to a single headphone worn by the listener in a remote room; and a stationary KEMAR listening condition, in which binaural recordings from an acoustic manikin placed in the listening room were delivered to a listener in the remote room. The listeners were presented one, two, or three simultaneous utterances. The results show that utterance identification was better in the normal listening condition than in the one-headphone condition, with the KEMAR listening condition yielding intermediate levels of performance. However, the differences between listening in the normal and in the one-headphone conditions were much smaller when two, rather than three, utterances were presented at a time. Localization performance was good for both the normal and the KEMAR listening conditions and at chance for the one-headphone condition. The results suggest that binaural processing is probably more important for solving the "cocktail party" problem when there are more than two concurrent sound sources.

Adolescent↗
PubMed2002

[Echolocation sound waves, morphological features and foraging strategies in Hipposideros pratti].

Studies on the echolocation sound waves in different states (flying and hanging), morphological features and ecological processes (foraging strategies, foraging habitat and diet type) of Hipposideros pratti showed that H. pratti had CF (constant frequency)-FM (frequency modulated) echolocation sounds. There were some differences in dominant frequency (caused by Doppler compensating effect), pulse repetition rate, pulse duration and interpulse interval between the bats at flying and hanging. The dominant frequency, FM bandwidth, pulse duration and interpulse interval were lower, while the pulse repetition rate and duty cycle were higher at flying than at hanging. All the differences indicated that H. pratti could adopt specific echolocation sounds to adapt to specific environments and conditions to detect, approach and capture their preys successfully. On the basis of echolocation sound and field observation, it was concluded that H. pratti might search the preys at flying in the period of insect fastigium, and after the period, it might search the targets at hanging. The foraging habitat was near the tree crowns, and the preys consisted mainly of relatively large insects, such as beetles.

Animals↗
PubMed2005

[Measurement technique for the cracking sounds during spinal manipulation].

OBJECTIVE: To design a set of equipment to collect, locate and analyze the cracking sounds during spinal manipulation. METHODS: On the basis of reviewing the current techniques for cracking sound measurement, we designed a cracking measurement system consisting of a pulse generator, transmission/reception interface, calibrating wave generator, compound sensors, computer, analytical software, and output components. RESULTS: Preliminary experiments demonstrated that the cracking sounds could be detected at a distance of 40 cm, suggesting that this system was technically feasible with some improvements to be made. CONCLUSION: This device can be used for collecting, locating and analyzing the cracking sounds during spinal manipulation.

Equipment Design↗
PubMed1991

Measurement of sound.

The measurement of sound involves the analysis of frequency, intensity, and temporal dimensions of acoustic signals. Each dimension of sound can be related directly to clinically observed phenomena. Frequency information, measured in Hz, can be extracted from pure-tone and complex stimuli. Intensity represents the physical energy of a signal and is described by using the decibel scale--a logarithmic scale of ratios. Temporal characteristics of sound include duration, phase, and repetition rate. In the analysis of human hearing sensitivity, the middle ear system and its impedance characteristics also must be considered. In this article, we have reviewed some major principles of sound and have presented a series of practical clinical applications. Such principles as these help to predict and explain frequency of laryngeal tones, middle ear mechanics, ear canal resonance, real-ear measurements of hearing aids, the Articulation Index, hearing loss, understanding of speech in quiet and in noise, and the relation between hearing and speech.

Acoustic Stimulation↗
PubMed1991

Vibroacoustic stimulation and intrauterine sound pressure levels.

The sound pressure level in amniotic fluid generated by vibroacoustic stimulation, assessed with a hydrophone placed close to the fetal head, was studied in 16 subjects. The mean recorded sound pressure level was 115 dB and the highest level was 129 dB. The range of the background noise was 63.5-80.5 dB. There was no obvious relationship between the distance from the stimulator to the hydrophone and the intrauterine sound pressure level. Although sound pressure levels are high, they are probably reduced before reaching the cochlea of the fetus because of the surrounding amniotic fluid and the fluid in the middle ear.

Acoustic Stimulation↗
PubMed1988

Dynamic auditory localization: perceived position of a moving sound source.

Experiments are presented in which a sound source was moved at 15.2 cm/s over a horizontal path of 60 cm length, positioned at a 57 cm distance in front of the observer, symmetrically relative to the median plane. The subjects had to localize the sound at different moments of time. The sound source was predominantly mislocated in the direction of the movement; the mislocation increased at the end of the movement by up to 10-11 deg. In another condition the sound source was localized when it was stationary. In this case the mislocation was directed towards the median plane. The differences between the static and dynamic auditory localization are discussed.

Auditory Perception↗
PubMed1984

Alteration in the low frequency lung sounds in respiratory disorders associated with crackles.

Lung sounds were recorded in three groups of 5 subjects, 2 conditions associated with pulmonary crackling (asbestosis and pulmonary oedema), and in normal non-smoking males. A technique was used which permitted extraction and analysis of the low-frequency sounds. Differences were evident in the 5-50 Hz range of the frequency spectra which allowed separation of all 3 groups. A prominent feature was the close similarity of the low-frequency sounds within the asbestos group when plotted on a scattergram. The findings suggest that alteration in low-frequency breath sound occurs in parenchymal lung disease and that its potential merits further investigation.

Asbestosis↗