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PubMedDate not supplied

MRI acoustic noise: sound pressure and frequency analysis.

The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The sound pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.

Calibration↗
PubMed1998

Matching of acoustic features during the vocal exchange of coo calls by Japanese macaques

A central issue in studies of vocalizations of non-human primates is the extent of their plasticity. Japanese macaques, Macaca fuscata, frequently utter coo calls and exchange these calls with other group members to maintain contact vocally. I conducted a playback experiment to examine whether monkeys that respond vocally match the acoustic features of their reply to those of the calls they have heard. Six to eight stimulus calls with different acoustic properties in terms of fundamental frequency components were played back to each of seven females, in an attempt to elicit replies from the subjects. There were significant positive regressions of the frequency range of stimuli with that of the replies. Japanese macaques thus matched some of the acoustic features of their replies to those of the preceding calls, suggesting that they might be able to modify the acoustic features of their calls according to the features of the prior calls of another group member.Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1991

Progressive hearing loss after single exposure to acute acoustic trauma.

Progressive hearing loss after single episodes of acute acoustic trauma (Knalltrauma) has been reported in only a few cases. Many authors dispute such a progressive evolution. Since this question is of obvious importance in cases evolving into lawsuits, its occurrence also arouses scientific interest. The present study reports 58 bilateral and 17 unilateral cases of acute acoustic trauma showing progression of more than 20 dB at least at one frequency. The mean follow-up time was more than 20 years. The incidence was estimated as less than 1% of cases involving acute acoustic trauma. The evolution of the progressive hearing loss did not show a specific pattern; in the unilateral group, there were no statistically significant differences between the progression in both ears. The findings clearly indicate that late progression of hearing loss due to single episodes of acute acoustic trauma does not exist unless the affected ear is exposed to additional damage not related to the initial trauma.

Adolescent↗
PubMed1993

Acoustic structure of vocalization and stapedius muscle activity during vocal development in chickens (Gallus gallus).

The link between stapedius muscle activity and acoustic structure of vocalization was analysed in cocks of age 20-30 to 90-100 days old. The results show that stapedius muscle activation depends on the acoustic structure of vocalization and changes during vocal development. This dependence was observed in spontaneous calls and in vocalizations elicited by stimulating the mesencephalic "calling area". In 30-day-old cocks stapedius muscle EMG response is never associated with vocalizations with an acoustic energy content which is always distributed at frequencies higher than 2000 Hz. The coupling between vocalization and stapedius muscle activity begins later, when birds produce vocalizations with acoustic energy shifted towards lower frequencies. Overall, stapedius muscle activity is related to a bird's production of high amplitude low frequencies. These results support the hypothesis that the primary role of the stapedius muscle during normal vocal development is to dampen the amplitude of low frequency energy that reaches the cochlea during vocalization.

Aging↗
PubMed1993

Enhancement of the acoustic startle response by stimulation of an excitatory pathway from the central amygdala/basal nucleus of Meynert to the pontine reticular formation.

The acoustic startle response (ASR) is a simple motor reaction to intense and sudden acoustic stimuli. The neural pathway underlying the ASR in rats is already fairly well understood. As the ASR is subject to a variety of modulations, this reaction can serve as a model for vertebrate neuroethologists to investigate the neural mechanisms mediating sensorimotor transfer and their extrinsic modulation. We report here on experiments in rats which were undertaken in order to investigate the neural mechanisms underlying the enhancement of the ASR. An increased amplitude of the ASR can be observed during states of conditioned and unconditioned fear. By employing neuroanatomical tract-tracing methods, we describe a pathway from neurons of the medial division of the central amygdaloid nucleus (cA) and the basal nucleus of Meynert (B) to the caudal pontine reticular nucleus (PnC), an important relay station in the acoustic startle pathway. Extracellular recordings from acoustically responsive neurons in the PnC showed that electrical stimulation of the cA/B facilitates the tone-evoked response of these neurons. Behavioural tests following chemical stimulation of the cA/B with NMDA (N-methyl-d-aspartate) in awake rats indicated that activation of this pathway increases the ASR. The lack of sufficient spatial resolution of our stimulation techniques did not allow us to differentiate the relative contributions of the cA and the B to this effect. As the amygdaloid complex has been implicated in emotional behaviour, particularly in the mediation of fear, these findings substantiate the concept that the amygdaloid complex plays a key role for the enhancement of the ASR by conditioned and unconditioned fear.

Amygdala↗
PubMed1995

GABA can improve acoustic contrast in the rat ventral cochlear nucleus.

The effect of microiontophoretically applied gamma-aminobutyric acid (GABA) and its agonists and antagonists on the response pattern of single units in the ventral cochlear nucleus (VCN) of the rat was examined in order to study GABA's physiological function in auditory processing. The effects of the drugs were judged by changes of spontaneous and sound-evoked activity in peristimulus-time histograms (PSTHs) of at least 20 consecutive presentations of acoustic stimuli. GABA inhibited the discharge activity of the majority of neurons. All response types found in the VCN except onset-I responders were sensitive to GABA. The GABAergic inhibition is most probably mediated by GABAA receptors, since the GABAA-receptor agonist muscimol, but not the GABAB-receptor agonist baclofen, mimicked the effect of GABA. The GABAA-receptor antagonists, bicuculline and picrotoxin, had an excitatory effect on the neurons' spontaneous activity, suggesting a tonic endogeneous release of GABA which exerts a permanent inhibition on VCN neurons. Although inhibitory, iontophoresis of GABA emphasized the response to stimulus onset in the PSTHs by means of a stronger inhibition of spontaneous activity. When using iontophoretical currents which did not suppress the neuronal activity completely, a strong inhibition of spontaneous activity was accompanied by only a small inhibition of tone-evoked activity. Under these conditions, the response to tone onset was frequently not inhibited at all. Therefore, GABA's physiological function is possibly to improve the contrast between transient acoustic signals and ongoing background activity. In order to test this hypothesis, the test tone was masked by continuous background noise. Indeed, GABA reduced the noise-evoked discharge more than the tone-evoked discharge, leaving the onset peak in the PSTHs almost unchanged. Thus, GABAergic input improves the signal-to-noise ratio for acoustic transients in VCN neurons. Our data suggest that a functional role of GABA in the VCN is to act as a transmitter within a descending inhibitory feedback loop of the auditory brainstem which serves to improve the transmission of relevant acoustic signals in constant background noise.

Animals↗
PubMed1977

Normal values of the ipsilateral acoustic stapedius reflex threshold.

It is frequently taken for granted that the acoustically evoked stapedius reflex is bilaterally symmetrical. Contrary to this, Møller described an asymmetry of the acoustic stapedius reflex with an ipsilaterally 2--14 dB lower threshold. The determination of normal values of the ipsilateral acoustic stapedius reflex threshold with a large number of patients is difficult as the intensity of the stimulus depends considerably on the position of the probe in the acoustic meatus and is therefore not defined with sufficient accuracy. For this reason we determined the values of the ipsilateral threshold by applying a stimulus sound of high intensity to the deaf ear of unilaterally completely deaf patients with a normal headphone, which can be calibrated much more accurately. After subtraction of the individual cross hearing loss, the exact ipsilateral intensity was obtained. By this method a stapedius reflex could be evoked with 49 of the 62 patients. By mathematical consideration of the data of the positive cases, as well as the maximum available intensities with the negative cases, determination of the median value of the ipsilateral threshold was possible: at 0.5 kHz 59 dB; at 1kHz 62.5 dB; at 2 kHz 67 dB; at 4 kHz approx. 67 dB. The difference between ipsilateral and contralateral stapedius reflex threshold was in the range of 15 dB. A new definition of the normal value for the ipsilateral measured Metz recruitment appears necessary.

Auditory Threshold↗
PubMed1992

Evidence for supporting cell mitosis in response to acoustic trauma in the avian inner ear.

Acoustic overstimulation can lead to sensory cell (hair cell) loss in the auditory epithelium. Damaged hair cells in the organ of Corti (the mammalian auditory end-organ) degenerate and are replaced by non-sensory cells (supporting cells) which construct an irreversible scar. In birds, however, auditory hair cells which are damaged by acoustic trauma or ototoxic drugs may be replaced by new hair cells. As first step in determining the mechanism of hair cell regeneration, we developed an assay for cell divisions in the auditory epithelium after acoustic trauma. The results of these experiments demonstrate that supporting cells in damaged regions of the auditory epithelium incorporate the DNA-specific marker bromodeoxyuridine as early as one day after noise exposure. We provide direct evidence that following acoustic insult to the avian inner ear, supporting cells which reside within the sensory epithelium divide near the luminal surface and repopulate the epithelium. These results suggest that supporting cells participate in scar formation during hair cell degeneration, and produce new cells for regeneration.

Animals↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 3. Effects of altering heart rate and P-R interval.

A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventricular pacemaker after destruction of the bundle of His to produce a chronic heart block. The heart rate and P-R interval were then varied independently and their influence on the spectra and acoustic transmission of the mitral M1 and aortic A2 valve closure sounds was studied. Results indicate that the major effects of varying the P-R interval are a strong change in the intensity of M1 and modifications of its acoustic transmission across the heart/thorax acoustic system. No similar influence is observed on the intensity and acoustic transmission of A2. Varying the heart rate has a small effect of the intensity of M1 but none on the intensity of A2. In addition, changes in either the P-R interval or the heart rate do not seem to modify the spectral profile of the intracardiac and thoracic M1 and A2 components.

Animals↗
PubMed1990

Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs. Part 2. Effects of neuromuscular blockade, sternotomy and pacemaker control, and a two-week recovery period.

The paper describes the effects of neuromuscular blockade, sternotomy and atrio-ventricular pacing, and a two-week recovery period on the spectra and acoustic transmission of mitral M1 and aortic A2 sound components in dogs. Results indicate that neuromuscular blockade does not affect the attenuation properties of the heart/thorax acoustic system even if it modifies the intensity of M1 and the phase of the transfer function. The immediate effect of sternotomy and cardiac pacing is an important increase in the attenuation of the heart/thorax acoustic system. This increased attenuation is different for both sounds (20 dB for M1 and 11 dB for A2) and disappears after a two-week recovery period. However, the resulting controlled dog model shows slightly different acoustic characteristics than those of the normal animal model.

Animals↗
PubMed1998

Development of a cardiac acoustic mapping system.

The authors describe a cardiac acoustic mapping system designed to acquire, analyse, and display the amplitude distribution of a phonocardiogram (PCG) recorded from 22 sites on the thorax. A new PCG envelope detection approach, implemented by analogue circuits, enables simultaneous sampling of PCG envelopes from the 22 sites at a rate of 250 Hz/channel. A calibration procedure removes channel-to-channel gain variations, and a coherent averaging of each PCG envelope over several cardiac cycles improves the signal-to-noise ratio. Time congruent samples from the 22 averaged PCG envelopes are then interpolated in 2D to generate the isoamplitude maps. Preliminary results show that the acoustic maps can help locate the source of heart sounds and murmurs, and characterise their radiation and propagation patterns. Cardiac acoustic mapping opens up new avenues for the study of the propagation of heart sounds and murmurs through the heart-thorax acoustic system. This technique could contribute to improvements in the diagnosis of valvular dysfunctions.

Calibration↗
PubMed1996

[Acoustic voice analysis. On documentation of voice rehabilitation after laser surgery laryngeal carcinoma resection].

Following curative minimal-invasive laser resection of T1-T3 laryngeal carcinomas, patients were subjected to an intensive voice rehabilitation. Therapy was effected twice a day for approximately 2 months, utilizing the concept of functional voice therapy. Before and after rehabilitation, acoustic analyses were made by using two different computer-supported measuring systems: (1) the "multidimensional voice program" (Kay Elementrics Corp.) and (2) a novel software program developed in Göttingen that includes a new voice quality parameter based on correlations between frequency bands. Acoustic analyses showed superiority of the glottal versus supraglottal compensatory phonation. Findings showed that not all acoustic parameters equally documented voice improvement after rehabilitation. The standard deviation of fundamental frequency was the only parameter showing a significant post-therapeutic improvement. A further suitable acoustic method proved to be the voice quality parameter that has been newly introduced by us. In contrast to analogous parameters of other methods, this approach is independent of the exact periodicity of the glottal excitation function, thus permitting reliable results to be obtained even with aphonic or heavily dysphonic voices.

Aged↗
PubMed2001

[Value of acoustic speech analysis for prognostic assessment of stuttering in children. Partial results of a prospective longitudinal study].

UNLABELLED: PRESENT STATE OF KNOWLEDGE: There are currently no known acoustic parameters by which stuttering children can be appraised which will predict their subsequent speech fluency. AIM: To explain the significance of factors which perpetuate stuttering by using computer-based speech analysis of fluent speech for a 1 1/2 year period and to relate acoustic analysis with clinical measurements of stuttering. Special attention was given to motor-oral and/or linguistic deficits. METHOD AND RESULTS: A prospective study of 58 pre-school children who stutter. Correlations were sought between acoustic variables in the severity and course of the stuttering with the influence of motor-oral and linguistic disturbances. 19 age-matched, normal-speaking children served as controls. A subdivision of the study group into different subgroups with particular motor-oral and/or linguistic problems showed that children whose stuttering coincides with a delayed speech development have a distinctly better prognosis for early remission. In most of these children the stuttering remitted to such a degree as the deficits causing the stuttering could be reappraised, which means simultaneous improvement of the linguistic competence. CONCLUSION: It was apparent that remission rate was much higher in those children who showed linguistic disturbances at the same time with stuttering. Within the stuttering group, subgroups showed a few correlations in several acoustic parameters, but these could not, as yet, be shown to give any prognostic markers in the routine diagnosis of children who stutter. If a child shows any danger-signs of acquiring stuttering on a more permanent basis, a careful diagnosis is necessary in order to find the individually underlying factors before any therapeutical procedure.

Child↗
PubMed2006

Acoustic microsensors--the challenge behind microgravimetry.

Acoustic microsensors are commonly known as high-resolution mass-sensitive devices. This is a restricted view in many chemical and biosensor applications, especially in liquids. Sensitivity to non-gravimetric effects is a challenging feature of acoustic sensors. In this review we give an overview of recent developments in resonant sensors including micromachined devices and also list recent activity relating to the (bio)chemical interface of acoustic sensors. Major results from theoretical analysis of quartz crystal resonators, descriptive for all acoustic microsensors are summarized, and non-gravimetric contributions to the sensor signal from viscoelasticity and interfacial effects are discussed. We finally conclude with some future perspectives.

Lab-On-A-Chip Devices↗
PubMed2000

Involvement of the human medial cerebellum in long-term habituation of the acoustic startle response.

Animal studies have shown an involvement of the cerebellar vermis in long-term habituation of the acoustic startle response, but not in short-term habituation. The aim of the present study was to investigate whether short-term and long-term habituation of the acoustic startle response are impaired in patients with medial cerebellar lesions. Five patients with midline cerebellar lesions due to surgery for astrocytoma and ten healthy, age- and sex-matched subjects were studied. Subjects received 40 acoustic startle stimuli each day on five successive days. Peak amplitudes of the startle response recorded at the orbicularis oculi and the sternomastoid muscles were obtained. Data were analyzed for response decrement within the training session of one day (short-term habituation) and for a decrease in the startle response across the five training days (long-term habituation). Short- and long-term habituation of the startle response recorded at the sternomastoid muscles could be achieved in controls and in cerebellar patients. However, long-term habituation of the blink component of the acoustic startle response recorded at the orbicularis oculi muscles was significantly impaired in patients with cerebellar lesions compared with control subjects, whereas short-term habituation was preserved in both groups. The present findings suggest that the medial cerebellum is involved in long-term habituation of the blink component of the startle response in humans.

Adolescent↗
PubMed1994

Measurement of left ventricular ejection fraction by acoustic quantification and comparison with radionuclide angiography.

Left ventricular (LV) ejection fraction (EF) is an important measure of systolic function, with radionuclide angiography being the accepted standard for its determination. Echocardiography is ideal for repeated measurements of EF, but most methods are either subject to error in the presence of regional wall abnormalities or require cumbersome off-line analysis. Acoustic quantification is a recently introduced method that allows for the continuous on-line display of LV cavity dimensions, but the on-line algorithm for the measurement of EF has not been validated against an independent standard in the clinical setting. This study attempted to validate acoustic quantification in the determination of EF by comparison with off-line echocardiographic analysis and radionuclide angiography in 54 patients referred for this latter procedure. Acoustic quantification correlated well with off-line analysis in both the apical 4-chamber (r = 0.89, n = 43) and 2-chamber (r = 0.86, n = 26) views. Similarly, it also correlated well with radionuclide angiography in the 4-chamber (r = 0.81, n = 44) and 2-chamber (r = 0.83, n = 26) views. The correlation between the 2 methods was further improved when only the last 30 patients were assessed (r = 0.91, n = 25 for 4-chamber views; r = 0.86, n = 16 for 2-chamber views). The correlation was worse in patients with regional asynergy (r = 0.69, n = 17 for 4-chamber views; r = 0.76, n = 10 for 2-chamber views). Moreover, acoustic quantification tended to underestimate EF when compared with radionuclide angiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Acoustic trauma in extracranial magnetic brain stimulation.

The effects of the magnetic coil acoustic artifact (MCAA) associated with extracranial magnetic field stimulation (EMFS) of the brain were studied in normal hearing rabbits. Spectral and intensity analyses showed that the MCAA is a high intensity transient signal with peak energy between 2 and 5 kHz, and peak amplitudes in the first 100-200 mu sec. At EMFS levels of 50-100% of maximum output (2.0 Tesla), the corresponding MCAA levels were 131-142 dB sound pressure level (peak hold) at the outer ear and amplified by the external meatus to reach 145-157 dB sound pressure level (SPL) at the position of the tympanic membrane in rabbits. Measurements of the acoustic middle ear muscle reflex (AMR) in non-anesthetized rabbits indicated that exposure to EMFS levels of 50-100% resulted in correspondingly increasing compound threshold shifts (CTS) and permanent threshold shifts (PTS) in the unprotected ears of the experimental animals. Auditory brain-stem responses (ABR) measures on the same and additional animals corroborated these findings. Morphological studies showed evidence of substantial cochlear trauma at EMFS levels as low as 50%, with increasing severity up to 100% EMFS. Morphological examination of inner ear structures following exposure to the MCAA in the acute preparation (fixed within hours after exposure) showed ruptures between pillar cells and a detached organ of Corti. Preparations examined 3 or more weeks after exposure showed damaged pillar cells, a widespread loss of outer hair cells, fused and fractured inner hair cell stereocilia, and kinocilium outgrowth on inner hair cells. Although this extremely short impulse contains approximately 2 orders of magnitude less acoustic energy than a continuous noise exposure of 131 dB for 15 min, it is substantially more injurious to the cochlea. The present findings suggest that the acoustic artifact produced by the EMFS coil in some clinical instruments may pose a potential risk for temporary and permanent hearing loss in patients and clinicians when held in close proximity to the unprotected ear. Initial studies suggest that the magnetic field alone did not appear to cause permanent hearing impairment. We recommend the use of ear protectors for the patient and clinician during EMFS as a precautionary measure to prevent possible hearing loss from the MCAA.

Animals↗
PubMed1975

Compound action potential and single acoustic nerve fibres activity generation: an equivalent neuron approach.

The peripheral acoustic system can be easily subdivided into three distinct subsystems: a mechanical one (middle ear and basilar membrane), the set of mechanical-to-neural transducers (the inner and outer hair cells) and the neural part. The functional behaviour of the external and middle ear is well known, but the processes concerned with the transduction of mechanical motion into neural activity are still under investigation. Actually the mechanism of transmission of information concerning acoustic stimuli to the central nervous pathways is not clearly known. On the basis of physiological knowledge, a mathematical model reproducing the pattern of activity of the acoustic nerve, in response to the most typical acoustic stimuli, is proposed. This has been simulated on a digital computer.

Action Potentials↗