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Results for “Acoustic Impedance Tests”

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At least 19 recordsLinked to original sources
PubMed2006

Modal decomposition method for acoustic impedance testing in square ducts.

Accurate duct acoustic propagation models are required to predict and reduce aircraft engine noise. These models ultimately rely on measurements of the acoustic impedance to characterize candidate engine nacelle liners. This research effort increases the frequency range of normal-incidence acoustic impedance testing in square ducts by extending the standard two-microphone method (TMM), which is limited to plane wave propagation, to include higher-order modes. The modal decomposition method (MDM) presented includes four normal modes in the model of the sound field, thus increasing the bandwidth from 6.7 to 13.5 kHz for a 25.4 mm square waveguide. The MDM characterizes the test specimen for normal- and oblique-incident acoustic impedance and mode scattering coefficients. The MDM is first formulated and then applied to the measurement of the reflection coefficient matrix for a ceramic tubular specimen. The experimental results are consistent with results from the TMM for the same specimen to within the 95% confidence intervals for the TMM. The MDM results show a series of resonances for the ceramic tubular material exhibiting a monotonic decrease in the resonant peaks of the acoustic resistance with increasing frequency, resembling a rigidly-terminated viscous tube, and also evidence of mode scattering is visible at the higher frequencies.

Acoustics↗
PubMed2005

Influence of environmental factors on the evolution of industrial noise-induced hearing loss.

The aim of the study is to investigate how environmental factors, associated with exposure to industrial noise, affect the development of chronic noise-induced hearing loss. The study was conducted on 186 male subjects working in two bottling plants, situated respectively in a small farming community, and in a medium-sized city with significant levels of noise pollution. Levels of occupational exposure were the same for the two groups. The subjects were selected by means of a preliminary medical examination, and exposed to tonal hearing tests and acoustic impedance tests. Statistical analysis was performed on hearing threshold values obtained at the frequencies of 500, 1000, 2000 and 4000 Hz. The comparison between the thresholds obtained in the two groups showed a statistically significant difference, especially at the frequency of 4000 Hz and for occupational exposure exceeding 17 yr. The results led us to conclude that environmental factors, and urban noise in particular, influence the onset and development of occupational acoustic trauma, and that those working in the country are significantly less affected than those in the city. Since occupational exposure was the same for both groups, their different responses must therefore be interpreted as due to differences in non-occupational exposure, in turn dependent on different opportunities for rest from noise and different levels of exposure to noise pollution.

Cities↗
PubMed1975

The application of acoustic impedance measurements to pediatric clinical practice.

This article provides background information on acoustic impedance testing and illustrates utilization of test results in pediatric clinical practice. Acoustic impedance measurement devices are presently being used successfully by hearing screening programs and by otorhinolaryngologists in clinical and hospital settings. As a diagnostic tool, the acoustic impedance bridge can have particular applicability in dealing withe young children and other difficult-to-test populations. Impedance measurements can provide physicians with objective information about the condition of the middle ear, oftentimes more accurately than either otoscopic examination or standard audiometry. The technique described can assist physicians in diagnosing middle-ear diseases and in monitoring the effects of otological treatment.

Acoustic Stimulation↗
PubMedDate not supplied

Otitis media and child development. Design factors in the identification and assessment of hearing loss.

Otitis media with effusion (OME) is the major cause of auditory dysfunction in preschool and early-grade schoolchildren. At especially high risk are children with cleft palate/lip; some groups of mentally retarded children; children from underprivileged communities and children with severe or profound sensorineural hearing loss. In neonates the major concern is to identify those with severe sensorineural hearing loss but awareness of the likelihood of OME is also vital. The hearing loss associated with OME in its early stages may be as small as 10--15 dB and in consequence conventional hearing tests employing pure tones are inadequate is screening procedures. Acoustic impedance testing has proved to be a practicable, acceptable, sensitive and efficient method of identification of OME in infants and children. Impedance measurement cannot, as yet, provide accurate assessment of hearing loss, but this is probably not a serious drawback. The primary requirement is to detect OME in order that swift and effective treatment can be instituted.

Acoustic Impedance Tests↗
PubMed1999

Mass hearing screening in kindergarten students.

OBJECTIVE: To determine the types of hearing losses identified by mass hearing screenings in the public school system. DESIGN: Prospective observational. PARTICIPANTS: Students enrolled in kindergarten in the public school system. SETTING: Major metropolitan area. MAIN OUTCOME MEASURES: (1) hearing screening tests performed by speech pathologists using an audiometer in a quiet room; (2) formal audiologic testing including pure tone audiometry, tympanograms, speech discrimination, and acoustic impedance testing in a sound proof booth. RESULTS: 140 students failed hearing screening on two separate occasions; 91(65%) underwent formal audiologic testing at Milwaukee Public School, 43% demonstrated conductive hearing losses, 14% demonstrated sensorineural losses and 43% demonstrated normal hearing. CONCLUSION: Mass hearing screening in the school system (1) is useful for detecting transient conductive hearing losses, (2) detects a significant number of sensorineural hearing losses and (3) has a very poor follow-through by the families of those students identified with hearing loss through the screening program.

Acoustic Impedance Tests↗
PubMed2005

[Patterns of hearing disorders in normal otoacoustic emissions].

OBJECTIVE: To analyze and outline patterns of hearing disorders in normal otoacoustic emissions. METHOD: Tests of pure tone audiometry, acoustic impedance test, auditory brainstem response (ABR), 40 Hz AERP,spontaneous otoacoustic emissions (SOAE), transient evoked otoacoustic emissions (TEOAE), distortion evoked otoacoustic emissions (DPEOAE)and imaging examinations of CT/MRI scan were performed on all 83 patients with hearing disorders. RESULT: Patterns of hearing disorders in normal otoacoustic emissions including (1) 68 patients with auditory neuropathy; (2) 2 patients with unilateral acoustic neuroma; (3) 3 patients with cortical deafness or central hearing loss; (4) 2 patients with hyperacusis; (5) 2 patients with functional deafness; (6) 6 patients with malingering. CONCLUSIONS: OAE tests play an important role in diagnosis and differential diagnosis of the patients with retrocochlear deafness, central hearing loss, nonorganic hearing loss and some other special hearing disorders.

Adolescent↗
PubMed1994

Measurements of the acoustic input impedance of cat ears: 10 Hz to 20 kHz.

The acoustic input impedence of the ear is a useful measure of the behavior of the middle ear and of its effect on the acoustics of the external ear. A high-impedance acoustic source with an integral microphone was designed for acoustic-impedance measurements. The source's Norton equivalent circuit was determined from measurements of the sound pressure it generated in known acoustic loads. Tests on simple acoustic configurations show errors in impedance measurements of less than 10% in magnitude and 7 degrees in angle over a frequency range from 10 Hz to 10 kHz with increasing errors at higher frequencies. Measurements at the tympanic membrane (TM) on five cat ears with widely opened middle-ear cavities show an impedance that is compliance-like below 0.3 kHz and approximately resistive above 2 kHz. With the cavities intact the impedance magnitude is somewhat larger for low frequencies, has a sharp maximum near 4 kHz, and at the highest frequencies is little affected by the state of the cavities. Impedance magnitude varies among ears by a factor of 3. The pressure reflection-coefficient that is determined from the impedance is frequency dependent with magnitude between 0.2 and 1. To characterize the motion transformation of the TM we calculate the ratio of tympanic-membrane volume velocity to the velocity of the mallear umbo, called here the kinematic area ATK. This complex quantity is constant with an angle of zero for frequencies below 0.6 kHz, but at higher frequencies both magnitude and angle of ATK vary with frequency.

Acoustic Impedance Tests↗
PubMed2005

[Influence of obstructive sleep apnea-hypopnea syndrome in children on hearing problem].

OBJECTIVE: To analyze the effects of obstructive sleep apnea hypopnea syndrome on hearing among children. METHODS: One hundred and forty three apnea children proved with overnight polysomnography received pure tone audiometry, acoustic impedance test, and lateral nasopharyngeal airway X-ray. Hearing threshold level and blood oxygen's saturation, apnea hypopnea index were analyzed. RESULTS: Among the 127 cases,63 cases had type C or B tympanograms, and 33 of them had lifted hearing threshold level. The remaining 64 cases had normal hearing and tympanograms. It was found correlation between the A/N ratio and blood oxygen's saturation, and no correlation between the A/N ratio and average of hearing threshold level. There was no correlation between AHI and average of hearing threshold level of each group. Hearing level can be improved after adenoidectomy or adenotonsillectomy. CONCLUSIONS: The upper airway obstruction due to adenotonsillar enlargement is common in children. It also affects the middle-ear impedance. Although short -term and mild degree of hypoxemia has few influence on hearing threshold level, it may affect cochlear function.

Acoustic Impedance Tests↗
PubMed1980

The neonatal acoustic reflex.

Probe tones from 220 Hz to 2 000 Hz were used to measure the static and dynamic acoustic impedance of 44 neonates. Acoustic reflex thresholds to broad band noise were obtained from every neonate tested when employing the higher frequency probe tones. The reflex threshold levels measured are similar to those of adults. The static impedance values are discussed to give a possible explanation of why reflex thresholds cannot be detected using conventional 220 Hz impedance bridges.

Acoustic Impedance Tests↗
PubMed1999

Acoustic reflex detection using wide-band acoustic reflectance, admittance, and power measurements.

The measurement of the acoustic reflex threshold is a basic component of the diagnostic audiological test battery that may subject patients to potentially harmful sound pressures. A wide-band acoustic impedance and reflectance system (D. H. Keefe, R. Ling, & J. C. Bulen, 1992) was investigated as a means of obtaining reflex thresholds at a reduced level and as a means of providing a more complete characterization of the reflex than current clinical methods provide. Reflex thresholds obtained by measuring changes in wide-band admittance, reflectance, and power were at least 8 dB lower than those obtained with the standard clinical technique. These reflex-induced changes were accounted for by a simple oscillator model of the middle ear, assuming that the acoustic reflex results in an increase in stiffness. The results support further investigation of reflectance-based measures of the acoustic reflex as a clinical tool and as a means of studying the reflex mechanism.

Acoustic Impedance Tests↗
PubMed1999

Topodiagnostic assessment of occupational noise-induced hearing loss using distortion-product otoacoustic emissions compared to the short increment sensitivity index test.

Because the efforts needed to produce an "automatic audiogram" by means of distortion-product otoacoustic emissions (DPOAE) are still experimental, their capacity to produce objective topodiagnostic information must still be defined. In the present study results of the short increment sensitivity index testing (SISI) test in 97 patients with noise-induced hearing loss (NIHL) were compared with those of a DP-gram. Pure tone, speech and impedance audiometry, SISI tests and DPOAE measurements were performed on all patients. SISI was measured in both ears of 93 patients and unilaterally in 4 patients. SISI was also determined at two frequencies in 46 patients. Six measurements were rejected because of conductive hearing losses in adjacent frequencies. In all, 230 measurements could be compared. After classifying topodiagnostic results of the SISI test and DP-gram into cochlear, inconclusive and retrocochlear lesions, statistically significant correlations were found and differences were noted in only 18% of cases. Findings demonstrated the superiority of DPOAE to the SISI test in obtaining topodiagnostic information about inner ear disease.

Acoustic Impedance Tests↗