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At least 613 records · Page 34Linked to original sources
PubMed1996

Characterization of sounds emanating from the human temporomandibular joints.

Sounds from the temporomandibular joint were recorded on audiotape from 238 individuals by placing microphones in both ears. The recordings were later digitized at a sample rate of 1.7 kHz with 10-bit resolution and stored on computer disk. At least two open-close cycles were assessed from each individual; 2707 different individual sounds were analysed in the time and frequency domains. The sounds were classified as: (a) single, short duration (clicks), (b) multiple, short-duration (creaks) and (c) long duration (crepitus). The sounds were further subclassified into either high or low amplitude by (i) the attack, which produced hard and soft categories and (ii) comparing the amplitude between sides-bilateral sounds were those with amplitudes differing by < 40 mV; the rest were unilateral. To establish the robustness of the classification 42 acoustic events were selected to be classified visually by three observers on two separate occasions. Intraobserver agreement was 82% (kappa = 0.75) while interobserver agreement was 60% (kappa = 0.71). Statistically significant differences were noted between all classifications of sound. These were most marked in the time domain. A simple, automated classification scheme was devised that was capable of categorizing the sounds with 82% agreement (kappa = 0.71) compared to a human observer.

Adolescent↗
PubMed2003

Tonotopic representation of missing fundamental complex sounds in the human auditory cortex.

The N1m component of the auditory evoked magnetic field in response to tones and complex sounds was examined in order to clarify whether the tonotopic representation in the human secondary auditory cortex is based on perceived pitch or the physical frequency spectrum of the sound. The investigated stimulus parameters were the fundamental frequencies (F0 = 250, 500 and 1000 Hz), the spectral composition of the higher harmonics of the missing fundamental sounds (2nd to 5th, 6th to 9th and 10th to 13th harmonic) and the frequencies of pure tones corresponding to F0 and to the lowest component of each complex sound. Tonotopic gradients showed that high frequencies were more medially located than low frequencies for the pure tones and for the centre frequency of the complex tones. Furthermore, in the superior-inferior direction, the tonotopic gradients were different between pure tones and complex sounds. The results were interpreted as reflecting different processing in the auditory cortex for pure tones and complex sounds. This hypothesis was supported by the result of evoked responses to complex sounds having longer latencies. A more pronounced tonotopic representation in the right hemisphere gave evidence for right hemispheric dominance in spectral processing.

Acoustic Stimulation↗
PubMed2003

[Sound localization cues of binaural hearing].

The ability to localize sound sources in space is of considerable importance to the human safety- and survival-system. Consequently the current scientific interest in improving the safety-standard i. e. in air-traffic control has provided a new momentum for investigating spatial hearing. This review deals with the nature and the relative salience of the localization cues. Localization refers to judgements of the direction and distance of a sound source but here we will deal with direction only. We begin with a short introduction into the so-called Duplex theory which dates back to John William Strutt (later Lord Rayleigh). The idea is that sound localization is based on interaural time differences (ITD) at low frequencies and interaural level differences (ILD) at high frequencies. If the head remains stationary neither a given ITD nor an ILD can sufficiently define the position of a sound source in space. On such a theoretical basis cones of confusion which open outward from each ear can be predicted ambiguously projecting any source on the surface of such a cone onto an interaural axis. Our restricted ability at localizing sound sources in the vertical median plane is another example of possible ambiguity. At the end of the 19th century scientists already realized that occlusion of the pinnae cavities decreases localization competence. As a result of later achievements in physics and signal-theory it became more obvious that the pinnae may provide an additional cue for spatial hearing and that the outer ear together with the head and the upper torso form a sophisticated direction-dependent filter. The action of such a filter is mathematically described by the so-called Anatomical Transfer Function (ATF). The spectral patterning of the sound produced by the pinnae and the head is most effective when the source has spectral energy over a wide range and contains frequencies above 6 kHz, that is it contains wavelengths short enough to interact with the anatomical characteristics of the outer ears. Scientific findings further suggest that spectral patterns like peaks and notches may also be exploited monaurally, albeit an a priori-knowledge at the central-auditive level concerning the corresponding transfer functions and relevant real-world sounds is required. Binaural spectral cues are more likely to play a major role in localization. They are derived from another transfer function, the so-called Interaural Transfer Function (ITF), being the ratio of the ATFs at the two ears. The contributions of all these cues may sometimes not be enough to prevent the listener from opting for the wrong direction. But things can be eased by allowing head-movements: More than 60 years ago science reasoned that small head movements could provide the information necessary to resolve most of the ambiguities. Recent studies have proved that these findings have been accurate all along.

Cues↗
PubMed2000

Application of a finite-element model to low-frequency sound insulation in dwellings.

The sound transmission between adjacent rooms has been modeled using a finite-element method. Predicted sound-level difference gave good agreement with experimental data using a full-scale and a quarter-scale model. Results show that the sound insulation characteristics of a party wall at low frequencies strongly depend on the modal characteristics of the sound field of both rooms and of the partition. The effect of three edge conditions of the separating wall on the sound-level difference at low frequencies was examined: simply supported, clamped, and a combination of clamped and simply supported. It is demonstrated that a clamped partition provides greater sound-level difference at low frequencies than a simply supported. It also is confirmed that the sound-pressure level difference is lower in equal room than in unequal room configurations.

Acoustics↗
PubMed2005

Characteristics of the audio sound generated by ultrasound imaging systems.

Medical ultrasound scanners use high-energy pulses to probe the human body. The radiation force resulting from the impact of such pulses on an object can vibrate the object, producing a localized high-intensity sound in the audible range. Here, a theoretical model for the audio sound generated by ultrasound scanners is presented. This model describes the temporal and spectral characteristics of the sound. It has been shown that the sound has rich frequency components at the pulse repetition frequency and its harmonics. Experiments have been conducted in a water tank to measure the sound generated by a clinical ultrasound scanner in various operational modes. Results are in general agreement with the theory. It is shown that a typical ultrasound scanner with a typical spatial-peak pulse-average intensity value at 2 MHz may generate a localized sound-pressure level close to 100 dB relative to 20 microPa in the audible (< 20 kHz) range under laboratory conditions. These findings suggest that fetuses may become exposed to a high-intensity audio sound during maternal ultrasound examinations. Therefore, contrary to common beliefs, ultrasound may not be considered a passive tool in fetal imaging.

Acoustic Stimulation↗
PubMed1994

Repeatability of measurements of normal lung sounds.

The stability of lung sounds measurements over time may influence their clinical usefulness. In the present study we investigated the temporal variability of the spectral pattern of normal lung sounds. Breath sounds from five healthy men were recorded on the trachea and at four locations over the chest wall. Each subject was studied twice with a time interval of 1 wk. On each occasion, measurements were done in duplicate, with a 30-min interval between recordings. Sounds were amplified, band-pass filtered (75 to 2,000 Hz) and digitized into a computer, and the average spectra of the inspiratory, expiratory, and background sounds were calculated. The variability of corresponding spectra were calculated between the daily duplicate (same-day variability, SDV) and between the two recording sessions (between-day variability, BDV). SDV was 32.8 +/- 12.0% during inspiration and 40.8 +/- 12.6% during expiration (p = 0.005). BDV was 36.9 +/- 11.3% during inspiration and 42.7 +/- 12.7% during expiration. These values were not significantly different from SDV except for sounds recorded from the interscapular region (SR). At this location the SDV was 28.2 +/- 7.2% during inspiration and 40.8 +/- 14.2% during expiration, and the BDV was 48.2 +/- 18.7% during inspiration and 77.6 +/- 22.3% during expiration (p < 0.05). The increased BDV at SR was found to be a result of slight differences in microphone position from the first session to the next. Similar changes in microphone position at the other recording sites did not alter the variability of lung sounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2002

Spectral characteristics of mechanical heart valve closing sounds.

BACKGROUND AND AIMS OF THE STUDY: In-vivo evaluation of cavitation is based on the registration of high-frequency pressure fluctuations that represent a mixture of both cavitation and valve closing sounds, and are difficult to separate. In order to extract the cavitation signal, a high-pass filter removing the closing sound is applied. Importantly, the cut-off frequency should be chosen based on the valve's resonance pattern. This could be determined in a cavitation-free, air-operated set-up. As air and water/blood have different physical properties that could influence resonance frequencies, it is necessary to correlate the frequency content of the closing sounds recorded in air to represent expected findings in fluid. The study aim was to characterize the impact of the surrounding media on resonance frequency of a sound source, and to develop a method capable of evaluating the spectral characteristics of mechanical heart valves. METHODS: Five different valves were investigated. An in-vitro set-up was developed where the valves were operated in an airflow-controlled setting without cavitation. The valve closing sounds were recorded and a spectral analysis was performed. The resonance frequency of a simple sound source was also recorded in water and air in order to evaluate the impact of the surrounding media. RESULTS: Resonance frequencies from the sound source measured in air increased 14% compared with corresponding measurements in water. These data were used to correct findings from the five valves that showed different spectral characteristics in air. The frequency at which 97.5% of the signal energy was contained ranged from 40.9 to 65.8 kHz. CONCLUSION: Using an airflow in-vitro model, it was possible to determine the frequency signature of different mechanical heart valves. This might provide the information needed to design the optimal high-pass filter when evaluating cavitation.

Culture Media↗
PubMed1990

[High-frequency components of occlusal sound in sliding movement].

We postulated that high-frequency components of the occlusal sound occurring due to the characteristic vibration of teeth can be useful data for confirmation of the stability in occlusion, and studied the high-frequency components in the cases both of an experimental sliding movement and a normal occlusion. The results obtained were as follows. 1. A study on high-frequency components of the occlusal sound in an experimental sliding movement. 1) A study on wave type of the occlusal sound revealed one damped oscillation in an impact form and two in a slide form. 2) Spectrum analysis of the damped oscillation showed a similar spectrum pattern with a peak existing between 16KHz or more and 17KHz or less in both impact and slide cases. 2. A study on high-frequency components of the occlusal sound in a normal occlusion case. 1) The wave type in occlusal sound we have observed in a normal occlusion group and in a prosthetic or operative group was as follows: One damped oscillation shown in an impact form and two damped oscillation in a slide form which were the same as those shown in the case where an interference device was attached. 2) Duration of the sliding movement was short in a normal occlusion group, but was prolonged in a prosthetic or operative group. 3) The incidence of the wave type in occlusal sound was 56.7% in a prosthetic or operative group as compared to 87.8% in a normal occlusion group in an impact form. In contrast, the incidence was 43.3% in a prosthetic or operative group as compared to 12.2% in a normal occlusion group in a slide form. Such difference in the incidence between the wave types suggested that high-frequency components of occlusal sound can be an index for judgement of the stability in occlusion.

Dental Occlusion↗
PubMedDate not supplied

Spectral analysis of breath sounds in normal newborn infants.

To determine whether breath sounds in newborns are different from those described in older subjects, fast Fourier transform and power spectra analysis were performed on recorded breath sounds from 14 normal newborns. A respiration-triggered sampling technique was applied to compare early, middle, and late phases of inspiration and expiration, using a thoracic impedance signal. Peak frequencies were found in the range described for normal breath sounds in older subjects, and the frequency range of breath sounds was similar to that reported for older children and adults. The difference in breath sound quality of normal newborns appears to depend on the sound intensity during expiration. In contrast to older subjects, newborns showed only slightly less sound intensity during expiration; in the late phases of inspiration and expiration this intensity was almost equal.

Female↗
PubMed1994

Representation of multiple sound sources in the owl's auditory space map.

The barn owl's inferior colliculus contains a retina-like map of space on which a sound generates a focus of activity whose position corresponds to the location of the sound source. When there is more than one source of sound, the sound waves sum and may generate spurious binaural cues that degrade the auditory image. We investigated the signal conditions under which neurons in the owl's auditory space map are able to resolve two simultaneously active sound sources. We recorded from space map neurons responding to sounds from a pair of speakers separated in azimuth by 45 degrees and mounted on a rotatable arm. Stimuli consisted of a sum of sinusoids or pseudorandom noise bursts emitted simultaneously and at equal overall levels. The characteristics of the sounds in each speaker were varied, and the neuron's response was plotted as a function of the speaker pair's position. When the speakers emitted different sets of summed sinusoids, the cells responded to each speaker separately; that is, the cells were able to resolve two separate targets. However, when the speakers emitted identical summed sinusoids generating binaural cues that were identical to those of a single phantom source between the two speakers, the neurons responded when the speakers were on either side of their receptive fields. By manipulating the amplitude at which each speaker emitted the various frequencies, we could control the position, number, and size of the phantom sources detected by the cell. The cells also resolved two separate sources when they emitted noise bursts that were statistically independent or temporally reversed versions of one another. Since the overall spectra of such waveforms are identical, we suggest that the space map relies on differences between noise bursts that exist over brief time spans.

Animals↗
PubMed1993

Rhythmic organization of the sound of infant crying.

The purpose of the present study was to examine the temporal morphology and rhythmic structure underlying the repeated bursts of expiratory sounds in a sustained bout of crying of twenty-three 1-month-old infants. Durations of expiratory sounds and bursts were determined from a 90-s bout of naturally occurring cries recorded in the home before feeding. Results indicated wide individual differences in temporal morphology between infants and within infant cry sounds. Binary spectrum analysis of the presence of expiratory sounds in the cry sound detected rhythms in temporal organization at a wide range of dominant frequencies. Spectral complexity (higher numbers of peaks in the power spectrum) was related to a longer time since infants were last fed and shorter expiratory sounds. Results emphasize the importance of viewing cries of young infants as dynamic signals. An ontogenetic history of the rhythms of infant cry sounds may contribute to understanding organismic and environmental experiences which contribute to development.

Child Behavior↗
PubMed1994

Sound localization in newborn human infants.

Newborns' localization of sounds was examined in two experiments that utilized different psychophysical procedures and imposed different task demands. The results of both experiments were consistent in indicating that neonates not only differentiate the hemifield of a sound source but have some capacity to localize a sound within the hemifields. Adjustment of their initial head turn angle following a within-hemifield shift in location of an ongoing sound indicated that head orientation in neonates is elicited not only by sound onset but also by changes in location of an ongoing sound. Thus, multiple stimulus parameters impact on this neonatal response. Results are related to research on sound localization in older infants, and discussed in light of early development of the central auditory system.

Arousal↗
PubMed2003

Tonotopic cortical representation of periodic complex sounds.

Most of the sounds that are biologically relevant are complex periodic sounds, i.e., they are made up of harmonics, whose frequencies are integer multiples of a fundamental frequency (Fo). The Fo of a complex sound can be varied by modifying its periodicity frequency; these variations are perceived as the pitch of the voice or as the note of a musical instrument. The center frequency (CF) of peaks occurring in the audio spectrum also carries information, which is essential, for instance, in vowel recognition. The aim of the present study was to establish whether the generators underlying the 100 m are tonotopically organized based on the Fo or CF of complex sounds. Auditory evoked neuromagnetic fields were recorded with a whole-head magnetoencephalography (MEG) system while 14 subjects listened to 9 different sounds (3 Fo x 3 CF) presented in random order. Equivalent current dipole (ECD) sources for the 100 m component show an orderly progression along the y-axis for both hemispheres, with higher CFs represented more medially. In the right hemisphere, sources for higher CFs were more posterior, while in the left hemisphere they were more inferior. ECD orientation also varied as a function of the sound CF. These results show that the spectral content CF of the complex sounds employed here predominates, at the latency of the 100 m component, over a concurrent mapping of their periodic frequency Fo. The effect was observed both on dipole placement and dipole orientation.

Acoustic Stimulation↗
PubMed2007

Hardness, elasticity, and ultrastructure of bonded sound and caries-affected primary tooth dentin.

Biomechanical properties of bonded dentin are important factors for resin restoration. We evaluated the hardness and elastic modulus of bonded sound and caries-affected primary tooth dentin using a one-step adhesive system, and observed the microstructure of the bonded interface. Six sound and six carious primary teeth were used. For sound teeth, flat occlusal dentin surfaces were prepared with a water-cooled high-speed diamond bur. For carious teeth, infected dentin was stained with a caries detector and removed with a water-cooled low-speed round steel bur and hand instruments. The prepared dentin was bonded with One-Up Bond F Plus (Tokuyama Dental Co., Tokyo, Japan). The resin-dentin interface and dentin beneath the interface were measured with a nano-indentation tester and observed with SEM and TEM. For both the carious and sound teeth, there was no significant difference between the hardness of the interfacial dentin and dentin 10-80 microm beneath the interface. However, the Young's modulus of the interfacial dentin was significantly lower than the dentin 40-80 microm (carious teeth) or 50-80 microm (sound teeth) beneath the interface. Both the hardness and Young's modulus of the interfacial dentin were not significantly different between the carious and sound teeth. Compared to the sound dentin, the hybrid layer on the caries-affected dentin was thicker and exhibited more complicated morphologic features. The thickness of the hybrid layers was generally less than 1 microm.

Dental Caries↗
PubMed1995

Sound production in Pituophis melanoleucus (Serpentes: Colubridae) with the first description of a vocal cord in snakes.

The pine, gopher, or bull snake (Pituophis melanoleucus) makes two different defensive sounds. Hisses are characterized by lack of frequency and amplitude modulation; bellows have a brief initial period of high-amplitude, broad-frequency sound followed by a longer period of lower-amplitude, constant-frequency sound. Both defensive sounds contain distinct harmonic elements. The modulation and harmonic nature of these sounds seems to be unique among snakes. The larynx of Pituophis is unusual in having an epiglottal keel, a dorsal expansion of the cricoid cartilage, previously proposed to contribute to sound production; however, this study shows that it plays only a small role in increasing the amplitude of bellows. Within the larynx of Pituophis is a "vocal cord," the laryngeal septum, which is a flexible, horizontal shelf of tissue that divides the anterior portion of the larynx. Removal of the laryngeal septum alters the defensive sounds and eliminates their harmonic elements. The laryngeal septum is unique among previously described vertebrate vocal cords or folds because it is supported by the cricoid (as opposed to arytenoid) cartilage and is a single (as opposed to bilaterally paired) structure.

Animals↗
PubMed1994

Frequency distribution of breath sounds as an indicator of bronchoconstriction during histamine challenge test in asthmatic children.

In order to study changes in respiratory sounds associated with acute bronchoconstriction and -dilatation, breath sounds of 11 children with asthma (age range, 10-14 years) were recorded at the chest and at the trachea during histamine challenge test and after subsequent bronchodilatation. The changes in frequency spectra of breath sounds were compared with simultaneous changes in forced expiratory volume in 1 second (FEV1). In seven children who responded to histamine with a decrease in FEV1 of more than 15%, there was a significant relationship between percentage change in FEV1 (delta FEV1) and percentage change in median frequency (delta F50) of expiratory breath sounds recorded at the chest (r = 0.865; beta = -0.706, P = 0.0001) and at the trachea (r = 0.888; beta = -1.12, P = 0.0001). The association between breath sound intensity and FEV1 was weaker. Based on ANOVA, the increase of F50 during the challenge test was significantly larger in children who responded to histamine than in those who were non-responsive (P = 0.0016). At the chest, a decrease of 15% in FEV1 corresponded to an increase of 8% in expiratory F50. The provocative dose of histamine inducing a decrease of 15% in FEV1 (PD15FEV1) and the provocative dose causing an increase of 8% in F50 (PD8F50) were significantly related (r = 0.927, P = 0.003). We conclude that spectral analysis of breath sounds can be used to indicate airway obstruction during bronchial challenge tests in children, and may be adapted for tests in pre-school children. The results suggest that the same mechanisms that induce airflow limitation due to inhaled histamine may generate an increase in frequency content of breath sounds in children with asthma.

Adolescent↗
PubMed1999

Effect of ambient respiratory noise on the measurement of lung sounds.

The effect of ambient sounds, generated during breathing, that may reach a sensor at the chest surface by transmission from mouth and nose through air in the room, rather than through the airways, lungs and chest wall, is studied. Five healthy male non-smokers, aged from 11 to 51 years, are seated in a sound-proof acoustic chamber. Ambient respiratory noise levels are modified by directing expiratory flow outside the recording chamber. Low-density gas (HeO2 = 80% helium, 20% oxygen) is used to modify airway resonances. Spectral analysis is applied to ambient noise and to respiratory sounds measured on the chest and neck. Flow-gated average sound spectra are compared statistically. A prominent spectral peak around 960 Hz appears in ambient noise and over the chest and neck during expiration in all subjects. Ambient noise reduction decreases the amplitude of this peak by 20 +/- 4 dB in the room and by 6 +/- 3.6 dB over the chest. Another prominent spectral peak, around 700 Hz in adults and 880 Hz in children, shows insignificant change, i.e. a maximum reduction of 3 dB, during modifications of ambient respiratory noise. HeO2 causes an upward shift in tracheal resonances that is also seen in the anterior chest recordings. Ambient respiratory noise explains some, but not all, peaks in the spectra of expiratory lung sounds. Resonance peaks in the spectra of expiratory tracheal sounds are also apparent in the spectra of expiratory lung sounds at the anterior chest.

Adolescent↗
PubMed2003

Sensory cues for sound localization in the cricket Teleogryllus oceanicus: interaural difference in response strength versus interaural latency difference.

Two potential sensory cues for sound location are interaural difference in response strength (firing rate and/or spike count) and in response latency of auditory receptor neurons. Previous experiments showed that these two cues are affected differently by intense prior stimulation; the difference in response strength declines and may even reverse in sign, but the difference in latency is unaffected. Here, I use an intense, constant tone to disrupt localization cues generated by a subsequent train of sound pulses. Recordings from the auditory nerve confirm that tone stimulation reduces, and sometimes reverses, the interaural difference in response strength to subsequent sound pulses, but that it enhances the interaural latency difference. If sound location is determined mainly from latency comparison, then behavioral responses to a pulse train following tone stimulation should be normal, but if the main cue for sound location is interaural difference in response strength, then post-tone behavioral responses should sometimes be misdirected. Initial phonotactic responses to the post-tone pulse train were frequently directed away from, rather than towards, the sound source, indicating that the dominant sensory cue for sound location is interaural difference in response strength.

Acoustic Stimulation↗