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At least 199 records · Page 11Linked to original sources
PubMed1980

[Acoustic nerve adaptation in chronic acoustic trauma].

The adaptation phenomenon of the the cochlear nerve in the highest frequency region was studied by means of electrocochleography in the group of 32 persons exposed to prolonged noise and with noise-induced, mild hearing loss (in the 4--6 kHz region) and in 19 persons under the same conditions of noise-exposure but, without any evidence of the hearing loss. The same investigations were performed in the group of 27 normal-hearing persons and non-exposed to noise. In the whole group of persons exposed to prolonged noise, disregarding their hearing condition the amplitude-decrease of the action potential of the cochlear nerve due to the adaptation procedure, was twofold in comparison to the non-exposed persons. The latency of this potential was longer in the whole group of exposed to noise persons than in the intact persons. It was presumed that this type of auditory nerve adaptation results infinitial, ultrastructural noise-damage within the basal turn of the cochlea. Basing on the obtained results it was postulated that the adaptation phenomenon in the highest-frequency region can serve as an indicator of early noise-induced malfunction of the cochlea which probably precedes the highest-frequency threshold elevation in conventional audiometry.

Adaptation, Physiological↗
PubMed2000

Influence of circumferential partial coating on the acoustic radiation from a fluid-loaded shell

Acoustic compliant coatings are a common approach to mitigate the radiation and scattering of sound from fluid-loaded submerged structures. An acoustic compliant coating is a coating that decouples an acoustic source from the surrounding acoustic medium; that is, it provides an acoustic impedance mismatch (different density and speed of sound product). Such a coating is distinct from an ordinary compliant coating in that it may not be resilient in the sense of low stiffness, but still provides an acoustic impedance mismatch. Ideally, the acoustic coating is applied uniformly over the entire surface of the fluid-loaded structure to minimize the acoustic radiation and scattering. However, in certain instances, because of appendages, it may not be practically possible to completely cover the surface of a fluid-loaded structure to decouple it from the adjacent acoustic medium. Furthermore, there may be some inherent advantages to optimizing the distribution of the coating around areas from which the acoustic radiation appears to be dominant. This would be analogous to the application of damping treatment to a vibrating structure in areas where the vibration levels are highest. In the case of the acoustic radiation the problem is more complex because of the coupling between the acoustic fluid and the structure. In this paper, the influence of a partial coating on the acoustic radiation from a fluid-loaded, cylindrical shell of infinite extent and excited by either a line force or an incident plane acoustic wave is examined. The solution to the response and scattered pressure is developed following the procedure used by the authors in previous work on the scattering from fluid-loaded plates and shells. The coating is assumed to be normally reacting providing a decoupling layer between the acoustic medium and the structure; that is, it does not add mass or stiffness to the base structure. The influence of added mass or stiffness of the coating can be included as an added inhomogeneity and treated separately in the solution.

Journal Article↗
PubMed1996

Reductions in bone strength after fluoride treatment are not reflected in tissue-level acoustic measurements.

Acoustic velocity measurements are used to estimate tissue-level bone strength after fluoride therapy for osteoporosis. However, acoustic measurements provide information about elasticity, not strength, and bone elasticity does not necessarily correlate with bone strength at a tissue level. The current study was undertaken to evaluate the effects of fluoride treatment on tissue-level acoustic velocities, and to determine the relationship between acoustic velocity and bone strength measured in the femur, femoral neck, and spine. Young adult rabbits were treated with either 0 or 100 parts per million of fluoride in their drinking water for six months. After treatment, the bones were harvested for measurement of tissue fluoride, bone strength, and acoustic properties. Acoustic velocities were measured in the femoral midshaft using an acoustic microscope with a 50 MHz transducer. Both longitudinal and transverse velocities were measured. After the initial acoustic measurements the bone specimens were treated to remove either the organic matrix or mineral, and the acoustic measurements were repeated. Fluoride treatment increased bone fluoride levels 7-8 fold and reduced all biomechanical parameters. Most notably the fracture force of the femoral neck was reduced by 25% (p < 0.005), and the fracture stress of the L-5 vertebra was reduced by 19% (p < 0.05). Fluoride treatment had no significant effect on any of the measured acoustic velocities. The elastic anisotropy of the bone was decreased by demineralization (p < 0.0001) and increased by removal of the organic matrix (p < 0.0001), but unaffected by fluoride treatment. Acoustic measurements were not correlated with bone strength in the femoral neck or femoral midshaft. There was a positive correlation between the longitudinal velocity measured in the femur and the vertebral fracture stress, but this was the only positive association between acoustic velocities and strength measurements. These data cast doubt on the utility of high frequency (>2 MHz) acoustic measurements for evaluating the efficacy of fluoride therapy, especially in the hip.

Acoustics↗
PubMed2005

Influence of intensive coronary care acoustics on the quality of care and physiological state of patients.

AIM OF THE STUDY: To evaluate the possible role of room acoustics on patients with coronary artery disease and to test the hypothesis that a poor acoustics environment is likely to produce a bad work environment resulting in unwanted sound that could adversely affect the patients. METHODS AND RESULTS: A total of 94 patients admitted to the intensive coronary heart unit at Huddinge University Hospital for evaluation of chest pain were included in the study. Patient groups were recruited during bad and good acoustics, respectively. Acoustics were altered during the study period by changing the ceiling tiles throughout the CCU from sound-reflecting tiles (bad acoustics) to sound-absorbing tiles (good acoustics) of similar appearance. Patients were monitored with regard to blood pressure including pulse amplitude, heart rate and heart rate variability. The patients were asked to fill in a questionnaire about the quality of the care, and a follow-up of rehospitalization and mortality was made at 1 and 3 months, respectively. There were significant differences between good and bad acoustics with regard to pulse amplitude in the acute myocardial infarction and unstable angina pectoris groups, with lower values during the good acoustics period during the night. The incidence of rehospitalization was higher for the bad acoustics group. Patients treated during the good acoustics period considered the staff attitude to be much better than during the bad acoustics period. CONCLUSION: A bad acoustics environment during acute illness may have important detrimental physiological effects on rehabilitation.

Acoustics↗
PubMed2002

Acoustic and perceptual consequences of articulatory rate change in Parkinson disease.

This study sought to characterize the relationship among voluntary rate modification, vocal tract acoustic output, and perceptual impressions of speech for individuals with idiopathic Parkinson disease (PD). Healthy control speakers were studied for comparison purposes. Four research questions were addressed: (1) How is rate modification evidenced in acoustic measures of segmental and global timing? (2) What is the impact of rate modification on measures of acoustic working space for select vowels and consonants? (3) What is the impact of rate modification on perceptual impressions of severity? (4) Are rate-induced changes in measures of acoustic working space related to perceptual impressions of severity? Speakers read the Farm Passage at habitual, slow, and fast rates. The vowels /i/, /ae/, /u/, and /A/ and the fricatives /s/ and /S/ were of interest. Acoustic measures included articulatory rate, segment durations, vowel formant frequencies, and first moment coefficients. Measures of acoustic working space for vowels and fricatives also were derived. The results indicated that temporal acoustic measures changed in the expected direction across rate conditions, with a tendency toward slightly faster rates for the PD group. In addition, the relative rate change for the Fast and Slow conditions compared to the Habitual condition was similar across groups. Rate did not strongly affect measures of acoustic working space for the PD group as a whole, but there was a tendency for slower rates to be associated with larger measures of acoustic working space. Finally, there was not a strong relationship between perceived severity and measures of acoustic working space across the rate continuum for either group. Rather, the relationship between perceived severity and measures of acoustic working space was such that the PD group exhibited smaller measures of acoustic working space and more severe perceptual estimates than the control speakers, irrespective of rate condition.

Aged↗