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At least 1,369 records · Page 76Linked to original sources
PubMed1998

[Peak sound pressure levels of gunshots from starter's pistols].

Starter's pistols are often bought for self-defense, but can also be used for criminal activities (e.g. assaults, etc.). When a starter's pistol is loaded with blank cartridges and is fired, a powerful shooting noise results. The level of the noise produced is high enough to cause acoustic trauma. For legal examinations and giving an expert opinion further information is needed about the power of such noise. We examined how high peak sound pressure levels were of the gunshots of blank cartridges and whether there existed any directional characteristics from the noise emissions. In all, 15 different models of starter's pistols of 8 different calibres were examined. In addition to blank cartridges, 8 mm tear gas cartridges were also examined. Four transducers were situated in the horizontal plane around the muzzle: 0 degree (shooting direction), 45 degrees, 90 degrees, and 180 degrees (towards the firer). The distances between the transducers and the muzzle were 25 cm, 50 cm, 100 cm, and 200 cm. At a distance of 1 m and in the 0 degree shooting direction the peak sound pressure levels of nearly all weapons tested exceeded 160 dB. At a shooting distance of 25 cm the peak sound pressure levels reached 181 dB. In addition, we observed a directional characteristic concerning the emission of noise: pistols produced higher peak sound pressure levels to the front than backwards towards the firer.

Equipment Design↗
PubMed2005

Sound strategy: acoustic aposematism in the bat-tiger moth arms race.

The night sky is the venue for an ancient arms race. Insectivorous bats with their ultrasonic sonar exert an enormous selective pressure on nocturnal insects. In response insects have evolved the ability to hear bat cries, to evade their hunting maneuvers, and some, the tiger moths (Arctiidae), to utter an ultrasonic reply. We here determine what it is that tiger moths "say" to bats. We chose four species of arctiid moths, Cycnia tenera, Euchaetes egle, Utetheisa ornatrix, and Apantesis nais, that naturally differ in their levels of unpalatability and their ability to produce sound. Moths were tethered and offered to free-flying naive big brown bats, Eptesicus fuscus. The ability of the bats to capture each species was compared to their ability to capture noctuid, geometrid, and wax moth controls over a learning period of 7 days. We repeated the experiment using the single arctiid species E. egle that through diet manipulation and simple surgery could be rendered palatable or unpalatable and sound producing or mute. We again compared the capture rates of these categories of E. egle to control moths. Using both novel learning approaches we have found that the bats only respond to the sounds of arctiids when they are paired with defensive chemistry. The sounds are in essence a warning to the bats that the moth is unpalatable-an aposematic signal.

Animals↗
PubMed2000

A gain-control mechanism for processing of chorus sounds in the afferent auditory pathway of the bushcricket Tettigonia viridissima (Orthoptera; Tettigoniidae).

The representation of alternative conspecific acoustic signals in the responses of a pair of local interneurons of the bushcricket Tettigonia viridissima was studied with variation in intensity and the direction of sound signals. The results suggest that the auditory world of the bushcricket is rather sharply divided into two azimuthal hemispheres, with signals arriving from any direction within one hemisphere being predominantly represented in the discharge of neurons of this side of the auditory pathway. In addition, each pathway also selects for the most intense of several alternative sounds. A low-intensity signal at 45 dB sound pressure level is quite effective when presented alone, but completely suppressed when given simultaneously with another signal at 60 dB sound pressure level. In a series of intracellular experiments the synaptic nature of the intensity-dependent suppression of competitive signals was investigated in a number of interneurons. The underlying synaptic mechanism is based on a membrane hyperpolarization with a time-constant in the order of 5-10 s. The significance of this mechanism for hearing in choruses, and for the evolution of acoustic signals and signalling behaviour is discussed.

Acoustic Stimulation↗
PubMed2001

Laser vibrometric studies of sound-induced motion of the body walls and lungs of salamanders and lizards: implications for lung-based hearing.

A laser Doppler vibrometer was used to measure the acoustic responses of different body surfaces of several species of salamanders and lizards. The lateral body wall over the lung displayed sound-induced motion up to 30 dB greater than the lateral head surface from 300-1,000 Hz in salamanders and from 200-2,500 Hz in lizards. The lateral body wall of lungless plethodontid salamanders showed no such enhanced motion to sound. The lateral body wall of lizards was more responsive than their tympanum to sound frequencies below about 1,250-2,000 Hz. The frequency of the peak response of lizard body walls matched the resonant frequency of a Helmholtz resonator with the volume and dimensions of their lungs. In contrast, the frequency of peak response of salamander body walls was well below the resonant frequencies calculated for both Helmholtz resonators and closed tubes with the dimensions and volumes of their lungs. Nonetheless, filling the lungs with saline dramatically reduced the responsiveness of the lateral body walls of both the lunged salamanders and the lizards. As previously demonstrated in anuran amphibians, the lateral body wall and lungs of salamanders and lizards may function in sound reception, especially at relatively low frequencies.

Acoustics↗
PubMed2001

Female-pitched sound-producing voice prostheses--initial experimental and clinical results.

In order to improve voice quality in female laryngectomees and/or laryngectomees with a hypotonic pharyngo-oesophageal segment, a sound-producing voice prosthesis was designed. The new source of voice consists of either one or two bent silicone lips which perform an oscillatory movement driven by the expired pulmonary air that flows along the outward-striking lips through the tracheo-oesophageal shunt valve. Four different prototypes of this pneumatic sound source were evaluated in vitro and in two female laryngectomees, testing the feasibility and characteristics of this new mechanism for alternative alaryngeal voice production. In vivo evaluation included acoustic analyses of both sustained vowels and read-aloud prose, videofluoroscopy, speech rate, and registration of tracheal phonatory pressure and vocal intensity. The mechanism proved feasible and did not result in unacceptable airflow resistance. The average pitch of voice increased and clarity improved in female laryngectomees. Pitch regulation of this prosthetic voice is possible with sufficient modulation to avoid monotony. The quality of voice attained through the sound-producing voice prostheses depends on a patient's ability to let pulmonary air flow easily through the pharyngo-oesophageal segment without evoking the low-frequency mucosal vibrations that form the regular tracheo-oesophageal shunt voice. These initial experimental and clinical results provide directions for the future development of sound-producing voice prostheses. A single relatively long lip in a container with a rectangular lumen that hardly protrudes from the voice prosthesis may have the most promising characteristics.

Aged↗
PubMed2000

The effect on sound generation of varying both gas flow rate and the viscosity of sputum-like gel in a simple tubular model.

Gas flows of 2, 3, and 4 L/min were directed through a sputum-like gel with viscosities of 100, 150, and 200 P and placed in a tube similar in diameter to a human segmental bronchus (4 mm), which was immersed in a bath of water. The sound produced by gas flow through the gel was recorded with a hydrophone. Sound data were subjected to time-expanded waveforms and fast Fourier transform (FFT) analysis. This study demonstrated that the number of crackles generated was directly related to the flow rate and inversely related to gel viscosity. The initial deflection width (IDW), two-cycle duration (2 CD), and peak-to-peak amplitude of crackles were significantly affected by the gas flow rate but not the viscosity of the gel. A lower gas flow rate generated crackles with longer IDW and 2 CD, but higher gas flow rates generated crackles with higher amplitude. Peak sound intensity measured from FFT increased as flow rate increased but decreased as the viscosity of the gel increased. At low gas flows, no gel-induced crackle sound was generated within the data capture window when the most viscous gel was examined. A digital video image of gas flow through the gel was captured, and this confirmed the absence of bubbles or slug formation at low flows through 200 P gel during the 3 seconds of data acquisition. This study describes some characteristics of crackles generated from different combinations of gas flow and gel viscosity and suggests that "coarse crackles" results from the explosion of gas bubbles in pulmonary secretions. Health care practitioners should consider the combined effect of rate of inspiratory gas flow and sputum viscosity during auscultation of patients' lungs.

Bronchi↗
PubMed2003

Distributed coding of sound locations in the auditory cortex.

Although the auditory cortex plays an important role in sound localization, that role is not well understood. In this paper, we examine the nature of spatial representation within the auditory cortex, focusing on three questions. First, are sound-source locations encoded by individual sharply tuned neurons or by activity distributed across larger neuronal populations? Second, do temporal features of neural responses carry information about sound-source location? Third, are any fields of the auditory cortex specialized for spatial processing? We present a brief review of recent work relevant to these questions along with the results of our investigations of spatial sensitivity in cat auditory cortex. Together, they strongly suggest that space is represented in a distributed manner, that response timing (notably first-spike latency) is a critical information-bearing feature of cortical responses, and that neurons in various cortical fields differ in both their degree of spatial sensitivity and their manner of spatial coding. The posterior auditory field (PAF), in particular, is well suited for the distributed coding of space and encodes sound-source locations partly by modulations of response latency. Studies of neurons recorded simultaneously from PAF and/or A1 reveal that spatial information can be decoded from the relative spike times of pairs of neurons - particularly when responses are compared between the two fields - thus partially compensating for the absence of an absolute reference to stimulus onset.

Acoustic Stimulation↗
PubMed2006

Stimulus and response repetition effects in the detection of sounds: evidence of obligatory retrieval and use of a prior event.

Three experiments were performed to examine the extent to which the time required to detect a probe sound is determined by the acoustic characteristics of a preceding prime sound and by the nature of the response made to the prime. The results of Experiment 1 revealed that the effect of frequency repetition was facilitative when a response was made to the occurrence of both the prime and the probe, but was inhibitory when a response was made only to the probe. In contrast, there was no significant effect of location repetition when responses were made to both prime and probe but there was a strongly inhibitory effect when a response was required only to the probe. These results suggest that the acoustic characteristics of the prime along with information about any response made to it, are used in preparing and executing a response to the probe. Experiment 2 was designed to disrupt the temporal link between prime and probe as a way to discourage such retrieval. The results of the experiment revealed that although a response was required to both the prime and probe, no significant effect of frequency repetition was apparent but a robust inhibitory effect of location repetition emerged. In the third experiment repetition effects both within a trial (i.e., prime to probe) and between trials (i.e., probe to prime) were examined. A facilitative effect of frequency repetition was apparent when the interval between sounds was brief, and an inhibitory effect of location repetition was apparent when the interval between sounds was relatively lengthy. Taken together these results suggest that even simple perceptual judgments may be influenced by retrieval of information about a previous processing episode and that effects of frequency repetition and location repetition may be mediated by different mechanisms.

Association Learning↗
PubMed2001

Differential effect of near-threshold stimulus intensities on sound localization performance in azimuth and elevation in normal human subjects.

The ability of humans to localize sounds remains relatively constant across a range of intensities well above detection threshold, and increasing the spectral content of the stimulus results in an improvement in localization ability. For broadband stimuli, intensities near detection threshold result in fewer and weaker binaural cues used in azimuth localization because the stimulus energy at the high- and low-frequency ends of the audible spectrum fall below detection threshold. Thus, the ability to localize broadband sounds in azimuth is predicted to be degraded at audible but near threshold stimulus intensities. The spectral cues for elevation localization (spectral peaks and notches generated by the head-related transfer function) span a narrower frequency range than those for azimuth. As the stimulus intensity decreases, the ability to detect the stimulus frequencies corresponding to the spectral notches will be more strongly affected than the ability to detect frequencies outside the range where these spectral cues are useful. Consequently, decreasing the stimulus intensity should degrade localization in both azimuth and elevation and create a greater deficit in elevation localization due to the narrower band of audible frequencies containing elevation cues compared to azimuth cues. The present study measured the ability of 11 normal human subjects to localize broadband noise stimuli along the midsagittal plane and horizontal meridian at stimulus intensities of 14, 22, and 30 dB above the subject's detection threshold using a go/no-go behavioral paradigm. Localization ability decreased in both azimuth and elevation with decreasing stimulus intensity, and this effect was greater on localization in elevation than on localization in azimuth. The differential effects of stimulus intensity on sound localization in azimuth and elevation found in the present study may provide a valuable tool in investigating the neural correlates of sound location perception.

Adult↗
PubMed2005

On the closing sounds of a mechanical heart valve.

In the 1994 Replacement Heart Valve Guidance of the U.S. Food and Drug Administration (FDA), in-vitro testing is required to evaluate the potential for cavitation damage of a mechanical heart valve (MHV). To fulfill this requirement, the stroboscopic high-speed imaging method is commonly used to visualize cavitation bubbles at the instant of valve closure. The procedure is expensive; it is also limited because not every cavitation event is detected, thus leaving the possibility of missing the whole cavitation process. As an alternative, some researchers have suggested an acoustic cavitation-detection method, based on the observation that cavitation noise has a broadband spectrum. In practice, however, it is difficult to differentiate between cavitation noise and the valve closing sound, which may also contain high-frequency components. In the present study, the frequency characteristics of the closing sound in air of a Björk-Shiley Convexo-Concave (BSCC) valve are investigated. The occluder closing speed is used as a control parameter, which is measured via a laser sweeping technique. It is found that for the BSCC valve tested, the distribution of the sound energy over its frequency domain changes at different valve closing speeds, but the cut-off frequency remains unchanged at 123.32 +/- 6.12 kHz. The resonant frequencies of the occluder are also identified from the valve closing sound.

Heart, Artificial↗
PubMed1976

"Presystolic" augmentation of diastolic heart sounds in atrial fibrillation.

In the presence of atrial fibrillation, the diastolic murmur of mitral stenosis can appear augmented during early systole before the mitral valve closure sound. This phenomenon has previously been thought to be due to increased blood flow velocity across the narrowing mitral valve orifice. We have observed patients in whom the third heart sound (S3) gallop, the diastolic flow murmur of atrial septal defect and mitral insufficiency and the initial muscular component of the first heart sound become more intense during this period with short, critically timed cycle lengths. This phenomenon appears to be neither peculiar to nor indicative of mitral stenosis and is probably a direct result of the initial muscular contraction of an underfilled ventricle. Either the contraction itself or the sudden deceleration of the rapidly moving flow of blood across the atrioventricular orifice may produce the sound.

Atrial Fibrillation↗
PubMed1979

Wide splitting of the first heart sound secondary to tricuspid valve endocarditis. A phonocardiographic-echocardiographic study.

A patient is described with tricuspid valve endocarditis in whom the vegetation interfered with valve closure resulting in marked wide splitting of the first heart sound. M-mode and two-dimensional echocardiographic studies detected the presence of a vegetation. Simultaneous phonocardiographic and echocardiographic studies documented the marked delay in tricuspid valve closure and differentiated wide splitting of the first heart sound from other causes of early and mid-systolic sounds. Following pulmonary embolization, the first heart sound returned to normal. Echocardiographic disappearance of the vegetation of the tricuspid valve was also noted. Regrowth of the vegetation again produced the abnormal phonocardiographic and echocardiographic findings.

Adult↗
PubMed1990

The intrauterine sound environment of the human fetus during labor.

Ten pregnant women near term with medical indications for internal monitoring during labor were studied to quantify the intrauterine sound environment. The intrauterine background noise was measured with a miniaturized hydrophone placed transcervically at the level of the fetal neck under ultrasonographic guidance. In eight women no cardiovascular noise was audible and the intrauterine noise consisted predominantly of low-frequency noise (less than 100 Hz) from 60 to 85 dB. Above 100 Hz, the sound pressure level was less than 60 dB, decreasing to 40 dB above 500 Hz. In only two women maternal cardiovascular sounds were audible during uterine relaxation and disappeared during uterine contraction. Maternal bowel sounds and maternal vocalization were well above the intrauterine background noise. Because of this relative quietness, we hypothesized that the fetal acoustic environment could be altered significantly during antenatal vibratory acoustic stimulation.

Acoustic Stimulation↗
PubMed1981

Single-unit activity in the auditory cortex of monkeys actively localizing sound sources: spatial tuning and behavioral dependency.

Single-unit recordings were made from the auditory cortex of unanesthetized rhesus monkeys which were trained to perform a second localization task. Recordings were made from 196 units in 4 animals. Five sound sources were located at 0 degrees (midline) and on either side at azimuths of 37.5 degrees and 75 degrees. Almost most units responded to each of the 5 sources, 49% of the units had peak firing rates for the source on the contralateral side at 75% azimuth. Another 26% of the units had peak firing rates at the 37.5 degrees contralateral location, while only 11% had peak rates for the ipsilateral locations. In order to determine whether the behavior of actively locating a sound source affected units in auditory cortex, response rates compared under two behavioral conditions: one which required the detection of a sound regardless of location and another condition which required identification of a sound's location. of the 196 units, 16 had different response rates for the two conditions, with 15 of the 16 units having higher evoked rates in the localization task. For the 16 units, the difference in firing rate was typically observed for a single speaker location. No correlation could be determined between a unit's location within the subdivisions of auditory cortex and its spatial tuning response properties or its dependency upon behavioral condition.

Animals↗
PubMed1987

The first heart sound during the isovolumetric contraction.

We make the first attempt to construct a qualitative theory covering the whole process of the major part of the first heart sound from an electrical activation to the phonocardiographic observations at the thorax. We calculate the amplitudes and frequencies of the radiated pressures during the isovolumetric contraction period generated by the muscular wall of the left ventricle and by the valves considered as a spherical shell and two-dimensional membranes, respectively. The analysis shows that both the hemodynamic and the valvular theory are able to explain most of the characteristic features of the first heart sound (linear relation between the amplitudes of the radiated pressure and the slope of the left ventricular pressure-time curve; directional polarity of the amplitudes; equidistant frequency peaks with a decline in amplitudes). However, existing magnitudes of the set of physiological parameters involved seems to favour the hemodynamic theory of the first heart sound. The aortic valve can be neglected as a source of sound. The initial conditions (like valve closure velocity), according to our theory, cannot be important. The predicted time-plot and frequency spectrum of the radiated pressure show a general resemblance with the recorded ones. It is essential to have considerably more quantitative acoustic data both for normal and diseased hearts for subsequent theoretical development.

Heart Auscultation↗
PubMed1991

Systematic sound preference in phonological disorders: a case study.

Systematic sound preference, where a group of sounds with the same manner of articulation is represented by one or two sounds in the production, is one of the characteristics of children with phonological disorders. This article examines the hypotheses advanced by Weiner (1981) for the phenomenon in the light of the data from a 7-year old Portuguese speaking child. The findings support some of the hypotheses, while providing counter evidence for one of them. They also point to the importance of word position and stress patterns in the systematicity of systematic sound preference.

Articulation Disorders↗
PubMed1984

Effects of sound frequency on behavioral and cardiac orienting in newborn and five-month-old infants.

Alert newborn and 5-month-old infants' responsivity to variations in spectral composition of a rattle sound was examined. Each child received four stimulus conditions: low-, mid-, and high-frequency bandpass-filtered rattles and an unfiltered broadband rattle. Stimuli were played through a single loudspeaker laterally positioned, and head orientation and cardiac responses to sound were recorded. Compared to other stimuli, the low-frequency sound elicited less head turning in both age groups, with this effect exaggerated in younger infants. Head orientation toward the mid-frequency, high-frequency, and broadband stimuli did not differ with age. For all conditions, latency and duration of newborns' head turning was longer than that of 5-month-olds. Newborns responded with cardiac deceleration only on trials when they failed to turn. When head turns occurred, an acceleratory cardiac response was obtained. Five-month-olds responded with reliable cardiac deceleration irrespective of head turning toward the sound. Heart rate change did not vary as a function of frequency at either age, suggesting that all stimuli were equally effective in eliciting the infant's attention.

Arousal↗
PubMed1993

Dental factors associated with temporomandibular joint sounds.

Dental factors commonly associated with signs and symptoms of temporomandibular disorders were investigated in a group of nonpatients. A highly sensitive technique was used to establish the presence of temporomandibular joint (TMJ) sounds. In a discriminant analysis nonworking side interferences, attrition, molar contacts, horizontal range of jaw movement, and morphologic occlusion contributed significantly to the prediction of sounds. Further study of morphologic aspects of the joint and stress-related parafunctions may contribute to the understanding of the development of TMJ sounds. We concluded that TMJ sounds are a fairly common sign associated with mild deviations in certain morphologic and functional aspects of the stomatognathic system.

Adult↗