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PubMed2003

Experimental setup for measurement of acoustic power dissipation in lined ducts for higher order modes propagation with air mean-flow conditions.

A flow duct acoustic facility was developed to measure liner efficiency in attenuating higher order acoustic duct modes propagation conditions with mean air flow. The method is based on measurement, upstream and downstream of a liner, of the acoustic power produced by a periodic source. Directly measured total or modal acoustic powers are deduced from the local measurement, in both cross sections, of acoustic pressure, axial acoustic particle velocity, and axial mean flow velocity which are supplied by a probe made of a microphone and a single hot film. In this paper, the equipment, signal processing, and the data treatment process of this facility are first described. Then, information on the accuracy of the methodology is provided by a validation test performed with a rigid wall duct section. Finally, the results of an experiment carried out with a locally reacting liner and a mean flow velocity of 20 m/s will be presented. Measurements of the main attenuation frequency and of the main total acoustic power dissipated agree with the values for which the liner was designed. These results point out the limitations of the method presented to sources with high-level periodic sounds to provide a sufficient signal-to-noise ratio, the noise being produced by fluctuations of the turbulent flow.

Journal Article↗

PubMed2004

Hybrid near-field acoustic holography.

Hybrid near-field acoustical holography (NAH) is developed for reconstructing acoustic radiation from an arbitrary object in a cost-effective manner. This hybrid NAH is derived from a modified Helmholtz equation least squares (HELS) formula that expands the acoustic pressure in terms of outgoing and incoming waves. The expansion coefficients are determined by solving an overdetermined linear system of equations obtained by matching the assumed-form solution to measured acoustic pressures through the least squares. Measurements are taken over a conformal surface around a source at close range so that the evanescent waves can be captured. Next, the modified HELS is utilized to regenerate as much acoustic pressures on the conformal surface as necessary and take them as input to the Helmholtz integral formulation implemented numerically by boundary element method (BEM). The acoustic pressures and normal velocities on the source surface are reconstructed by using a modified Tikhnov regularization (TR) with its regularization parameter determined by generalized cross validation (GCV) method. Results demonstrate that this hybrid NAH combines the advantages of HELS and inverse BEM. This is because a majority of the input data are regenerated but not measured, thus the efficiency of reconstruction is greatly enhanced. Meanwhile, the accuracy of reconstruction is ensured by the Helmholtz integral theory and modified TR together with GCV method, provided that HELS converges fast enough on the measurement surface. Numerical examples of reconstructing acoustic quantities on the surface of a simplified engine block are demonstrated. [Work supported by NSF.]

Journal Article↗

PubMed2004

Nonperturbing measurements of spatially distributed underwater acoustic fields using a scanning laser Doppler vibrometer.

Localized changes in the density of water induced by the presence of an acoustic field cause perturbations in the localized refractive index. This relationship has given rise to a number of nonperturbing optical metrology techniques for recording measurement parameters from underwater acoustic fields. A method that has been recently developed involves the use of a Laser Doppler Vibrometer (LDV) targeted at a fixed, nonvibrating, plate through an underwater acoustic field. Measurements of the rate of change of optical pathlength along a line section enable the identification of the temporal and frequency characteristics of the acoustic wave front. This approach has been extended through the use of a scanning LDV, which facilitates the measurement of a range of spatially distributed parameters. A mathematical model is presented that relates the distribution of pressure amplitude and phase in a planar wave front with the rate of change of optical pathlength measured by the LDV along a specifically orientated laser line section. Measurements of a 1 MHz acoustic tone burst generated by a focused transducer are described and the results presented. Graphical depictions of the acoustic power and phase distribution recorded by the LDV are shown, together with images representing time history during the acoustic wave propagation.

Journal Article↗

PubMed2005

Reconstruction of transient acoustic radiation from a sphere.

Transient near-field acoustical holography (NAH) formulation is derived from the Helmholtz equation least squares (HELS) method to reconstruct acoustic radiation from a spherical surface subject to transient excitations in a free field. To facilitate derivations of temporal solutions, we make use of the Laplace transform and expansion in terms of the spherical Hankel functions and spherical harmonics, with their coefficients settled by solving a system of equations obtained by matching an assumed-form solution to the measured acoustic pressure. To derive a general form of solution for a temporal kernel, we replace the spherical Hankel functions and their derivatives by polynomials, recast infinite integrals in the inverse Laplace transform as contour integrals in a complex s-plane, and evaluate it via the residue theorem. The transient acoustic quantities anywhere including the source surface are then obtained by convoluting the temporal kernels with respect to the measured acoustic pressure. Numerical examples of reconstructing transient acoustic fields from explosively expanding, impulsively accelerating, and partially accelerating spheres, and that from a sphere subject to an arbitrarily time-dependent excitation are depicted. To illustrate the effectiveness of HELS-based transient NAH formulations, all input data are collected along an arbitrarily selected line segment and used to reconstruct transient acoustic quantities everywhere.

Journal Article↗

PubMed2006

Acoustic structures in the alarm calls of Gunnison's prairie dogs.

Acoustic structures of sound in Gunnison's prairie dog alarm calls are described, showing how these acoustic structures may encode information about three different predator species (red-tailed hawk-Buteo jamaicensis; domestic dog-Canis familaris; and coyote-Canis latrans). By dividing each alarm call into 25 equal-sized partitions and using resonant frequencies within each partition, commonly occurring acoustic structures were identified as components of alarm calls for the three predators. Although most of the acoustic structures appeared in alarm calls elicited by all three predator species, the frequency of occurrence of these acoustic structures varied among the alarm calls for the different predators, suggesting that these structures encode identifying information for each of the predators. A classification analysis of alarm calls elicited by each of the three predators showed that acoustic structures could correctly classify 67% of the calls elicited by domestic dogs, 73% of the calls elicited by coyotes, and 99% of the calls elicited by red-tailed hawks. The different distributions of acoustic structures associated with alarm calls for the three predator species suggest a duality of function, one of the design elements of language listed by Hockett [in Animal Sounds and Communication, edited by W. E. Lanyon and W. N. Tavolga (American Institute of Biological Sciences, Washington, DC, 1960), pp. 392-430].

Animals↗

PubMed1997

The acoustic features of vowel-like grunt calls in chacma baboons (Papio cyncephalus ursinus): implications for production processes and functions.

The acoustic features of 216 baboon grunts were investigated through analysis of field-recorded calls produced by identified females in known contexts. Analyses addressed two distinct questions: whether the acoustic features of these tonal sounds could be characterized using a source-filter approach and whether the acoustic features of grunts varied by individual caller and social context. Converging evidence indicated that grunts were produced through a combination of periodic laryngeal vibration and a stable vocal tract filter. Their acoustic properties closely resembled those of prototypical human vowel sounds. In general, variation in the acoustic features of the grunts was more strongly related to caller identity than to the social contexts of calling. However, two acoustic parameters, second formant frequency and overall spectral tilt, did vary consistently depending on whether the caller was interacting with an infant or participating in a group move. Nonetheless, in accordance with the general view that identity cueing is a compelling function in animal communication, it can be concluded that much of the observed variability in grunt acoustics is likely to be related to this aspect of signaling. Further, cues related to vocal tract filtering appear particularly likely to play an important role in identifying individual calling animals.

Animals↗

PubMed2006

Glucocorticoid receptor and nuclear factor-kappa B interactions in restraint stress-mediated protection against acoustic trauma.

The role of glucocorticoid receptors (GRs) in the protective effect of restraint stress (RS) before acoustic trauma was studied in spiral ganglion neurons of CBA mice. RS increased corticosterone and protected against elevated auditory brain stem thresholds caused by acoustic trauma. This protection was inhibited by the pretreatment with a corticosterone synthesis inhibitor, metyrapone (MET), and a GR antagonist (RU486). RS followed by acoustic trauma caused an immediate increase in corticosterone that triggered nuclear translocation of GR, without a change in the expression of GR protein. RU486 + MET before RS and acoustic trauma caused an immediate increase in GR mRNA followed by increased GR protein expression (24 h after trauma). GR signaling was further characterized by analyzing nuclear factor-kappaB (NF kappaB) nuclear translocation and protein expression. NF kappaB nuclear translocation was reduced after acoustic trauma or pretreatment with RU486 + MET before RS and acoustic trauma. On the contrary, RS protected against the trauma-induced NF kappaB reduction of its nuclear translocation in inhibitory-kappaB (I kappaB)-dependent manner. RU486 + MET caused a simultaneous decreased I kappaB expression and NF kappaB nuclear translocation, demonstrating an interference with the I kappaB-mediated activation of NF kappaB. In summary, RS protects the cochlea from acoustic trauma by increasing corticosterone and activating GRs. These results emphasis how GR activity modulates hearing sensitivity and its importance for the rationale use of glucocorticoids in inner ear diseases.

Animals↗

PubMed1998

[The role of acoustic rhinometry in the evaluation of the volume of nasopharynx before and after adenoidectomy].

OBJECTIVE: To determine the type of acoustic rhinometry curve in different kinds of nasal and nasopharyngeal diseases and the role of acoustic rhinometry in the evaluation of the changes of the volume of nasopharynx before and after adenoidectomy. METHODS: One hundred and fifty-one patients with nasal and nasopharyngeal diseases, including rhinitis, nasal polyps, obstructive sleep apnea syndrome, palatoschisis, atrophic rhinitis, adenoid vegetation, perforation of nasal septum, carcinoma of nasopharynx, and stricture of nasal limen, were measured with acoustic rhinometry. Meanwhile, 15 patients with adenoid vegetation were measured before and after adenoidectomy, the changes in volume recorded by acoustic rhinometry were compared with the adenoid volume obtained by the method of displacement. RESULTS: Acoustic rhinometry curve can be divided into normal and abnormal curves and the abnormal curves can be divided into four types according to the site of changes. Acoustic rhinometry curve altered with the changes in character, degree and site of nasal and nasopharyngeal diseases and could return to normal after surgery or medical treatment. The volume of nasopharynx of adenoid vegetation patients was significantly smaller than that of the normal control and it rose significantly and became closed to normal after adenoidectomy. The volume of adenoid and the calculated changes in volume of the nasopharynx was found to be interrelated and highly significant(r = 0.87, P < 0.001). CONCLUSION: The results indicate that acoustic rhinometry curve is a useful method in the assistant diagnosis and judgment of therapeutic effectiveness of many kinds of nasal and nasopharyngeal diseases and can provide reference for the evaluation of the volume of adenoids.

Adenoidectomy↗

PubMed1992

[Acoustic frequency analysis of auscultation findings in neonates].

The authors analyzed 280 auscultation findings of 35 neonates with birth weights of 1800-4500 g and 65 pathological neonates with birth weights of 1150-3600 g. For recording of the auscultation findings an electronic phonendoscope EST 40 (Bosch) was used and the finding was recorded on a microtape recorder (Olympus). The frequency analysis was made on a Sonagraf analyzer (Kay Elemetric), using a 45 Hz filter a time range of 2.4 sec. From the results of the work ensues that in physiological neonates two basis types of sonagrams can be detected: 1. the record presenting itself as a continuous zone of noise with maximal cumulation of acoustic energy up to 500 Hz where the ratio of acoustic energy is equal in both stages of the respiratory cycle. The clinical correlate is "alveolar respiration". 2. a record with a discontinuous zone of noise with a more expressive ratio of acoustic energy up to 2500 Hz during inspiration. The clinical correlate is "sharper bronchoalveolar respiration". In the group of pathological neonates with different pneumopathies further sonagraphic phenomena were detected: a) "rales" as discontinuous acoustic phenomena persisting for 7-35 msec with a frequency range up to 3000 Hz, without a harmonious structure, present during inspiration as well as expiration, b) "transmitted phenomena"--discontinuous acoustic phenomena persisting for 75-150 msec with a frequency range up to 6000 Hz, without a harmonious structure, c) "wheezing"--continuous acoustic phenomena with a clearly marked harmonious acoustic structure lasting 540 +/- 240 msec with a frequency of the basic sound of 500 +/- 240 msec.(ABSTRACT TRUNCATED AT 250 WORDS)

Auscultation↗

PubMed2005

[Effectiveness of pharmacologic therapy combined with hyperbaric oxygen in sensorineural hearing loss following acute acoustic trauma. Preliminary report].

UNLABELLED: Exposure to loud sounds can cause acute acoustic trauma and permanent sensorineural hearing loss. The aim of the study was to evaluate effectiveness of pharmacological treatment combined with the hyperbaric oxygen (HBO) in the treatment of sensorineural hearing loss following acute acoustic trauma for patients treated in the Department of Otolaryngology of Military Institute of Health Service and Warsaw Center for Hyperbaric Therapy and Wounds Treatment. MATERIAL AND METHODS: Group of 12 patients (22 damaged ears) with acute acoustic trauma (10 men and 2 women), 16-67 years of age, mean age 28 years, was involved in our study. Patients with tinnitus and sensorineural hearing loss of minimum 15 dB at 0.25-8 kHz were included in the treatment group. Hearing gain of minimum 10 dB at 0.25-8 kHz and decrease in the intensity of tinnitus was considered as an improvement. 4 days was the mean time interval between acoustic trauma and starting the pharmacological treatment, 7 days was the mean time interval for the hyperbaric oxygen therapy commencement. RESULTS: Statistically significant difference in Pure Tone Audiometry results obtained before and after the treatment was noted in 4 kHz when considering all damaging factors that caused acoustic trauma and in 6 kHz only for damage resulting form shooting. Statistically significant difference was noted in 6 kHz if the HBO therapy was continued over 10 days (p < 0.00001). Statistically significant difference was noted in 4, 6, 8 kHz when treatment was started within 5 days since the acoustic trauma (p < 0.000001). CONCLUSIONS: Hyperbaric oxygen therapy is the unique method of increasing concentration of oxygen in the inner ear fluids thus facilitates the regeneration process. Hyperbaric oxygen therapy combined with steroids is an effective method of sensorineural hearing loss treatment following acute acoustic trauma.

Adolescent↗

PubMed1988

Acute acoustic trauma: dynamics of hearing loss following cessation of exposure.

The natural history of individuals with acute acoustic trauma who ceased to be exposed to impact noise was examined. Retrospective follow-up was carried out for 4 years on patients who were qualified as disabled following acoustic trauma with permanent threshold shift. Eight hundred forty-one individuals (1682 ears) were examined, of which 1514 ears with acoustic trauma were included in the study group; 150 individuals (300 ears) who continued to be exposed to impact noise even after discovery of acoustic trauma comprised the control group. In the latter, as long as exposure to gunfire continued, the severity of acoustic trauma increased. In the study group, during the first year after injury, changes were observed in hearing, whether improvement or deterioration; after this period, hearing loss appeared to be final. We suggest that, after 1 year following acute acoustic trauma, the associated hearing loss be considered as final, provided there is no further exposure to noise. This finding holds great importance from the medicolegal standpoint, an aspect that is unclear in the literature. It clarifies that beyond the period of 1 year after initial exposure, the pathologic process ceases (as long as there is no additional exposure to noise or gunfire). Further hearing deterioration beyond this period is not related to the initial acoustic trauma but rather to other factors.

Acute Disease↗

PubMed1994

Cell division in the gerbil cochlea after acoustic trauma.

The recent discovery of hair cell regeneration in the avian inner ear raises the possibility that hair cell regeneration might occur in the mammalian cochlea as well. The authors used 3H-thymidine labeling to detect mitotic activity in the cochleas of normal 3-week old gerbils exposed to acoustic trauma. Following an acoustic insult that caused progressively more severe damage in an apical to basal progression, 3H-thymidine was injected for 5 days. Control animals were not exposed to the acoustic insult. The gerbils' cochleas were sectioned and processed for autoradiography. In the control cochleas, there were extremely rare labeled cells in the stria, the spiral ligament, and the glial cells around the acoustic nerve fibers. In the damaged cochleas, no evidence of hair cell regeneration or of any cell division within the normal sensory epithelial structures was seen. Three labeled cells were seen in intercellular spaces within the sensory epithelium; they appeared to be macrophages. Frequent cell division was seen in numerous other regions of the damaged cochleas and among glial cells adjacent to the acoustic nerve fibers. It is concluded that there is no evidence for hair cell regeneration following acoustic trauma in the gerbil, but acoustic trauma does induce cell division in numerous other areas of the cochlea.

Animals↗

PubMedDate not supplied

Acoustic-reflex responses in patients with insulin-dependent diabetes mellitus.

PURPOSE: Patients with insulin-dependent diabetes mellitus (IDDM) are especially susceptible to microangiopathic complications such as nephropathy, retinopathy, and neuropathy. Microangiopathic changes are also the most important findings in histopathologic studies of the inner ear and central nervous systems in diabetic subjects. No previous studies have measured acoustic-reflex latencies (ARL) or amplitudes (ARA) in patients with IDDM. ARL and ARA reflect the function of the acoustic-reflex arch. Furthermore, possible changes in the tympanic membrane, ossicular chain, and stapedius muscle may affect the shape of acoustic-reflex. SUBJECTS AND METHODS: Acoustic-reflex thresholds, latencies, and amplitudes were studied in 53 patients with IDDM and 42 randomly selected nondiabetic control subjects, aged between 20 and 40 years, using the Madsen Model ZO 73 Impedance Bridge (Madsen Electronics, Copenhagen, Denmark). Subjects with an abnormal tympanic membrane, conductive hearing loss, and known cause for hearing impairment eg, noise damage, were excluded from the study. RESULTS: There were no differences between control and diabetic subjects in the contralateral acoustic-reflex thresholds. In contrast, patients with IDDM had longer ARLs and decreased ARAs compared with those of control subjects. ARA amplitude had linear correlation with the amplitude of tympanogram, whereas ARL had no linear correlation with auditory brainstem latencies in the same study subjects. Acoustic-reflex responses in insulin-dependent diabetic patients were not associated with the duration of diabetes, metabolic control, microangiopathy, or neuropathy. CONCLUSIONS: Prolonged ARLs and decreased ARAs in patients with insulin-dependent diabetes are probably caused more by the stiff middle ear system than disturbances in the brainstem.

Acoustic Impedance Tests↗

PubMed2026

Transient acoustic stimulation induces time-dependent synaptic remodeling and enhancement of auditory nerve output after threshold recovery.

BACKGROUND: Acoustic stress can alter cochlear function even in the absence of permanent threshold elevation; however, synaptic consequences of transient acoustic stimulation remain incompletely understood. OBJECTIVE: This study aimed to investigate whether transient acoustic stimulation induces changes in the auditory nerve output and cochlear ribbon synapse morphology following hearing threshold recovery. METHODS: Young adult CBA/CaJ mice were exposed to band-limited acoustic stimulation (45-2,000 Hz, 95 dB SPL, 2 h). Auditory brainstem responses (ABRs), hair cell and spiral ganglion neuron survival, and synaptic morphology were evaluated before exposure and up to 2 weeks post-exposure. RESULTS: ABR thresholds were transiently elevated immediately after exposure but largely recovered by 1 day post-exposure. In contrast, ABR wave I amplitudes significantly increased after threshold recovery across multiple test frequencies. Ribbon-associated puncta in both inner and outer hair cell regions exhibited biphasic temporal changes, with an initial decrease immediately after exposure followed by an increase at 1 day post-exposure. The ribbon-associated punctal area also increased after exposure and remained elevated at later post-exposure time points. No significant loss of hair cells or spiral ganglion neurons was observed. Exploratory genomic analysis suggested enrichment of pathways related to metabolic defense and cellular stress responses. CONCLUSIONS: Transient acoustic stimulation induces time-dependent synaptic remodeling and enhancement of peripheral auditory nerve output without overt cellular degeneration. These findings support a model in which early cochlear responses to acoustic perturbation include adaptive synaptic plasticity and gain regulation, extending current concepts of noise-induced cochlear change beyond irreversible synaptic loss.

Animals↗

PubMedDate not supplied

Sudden hearing loss as a presenting symptom of acoustic neuroma.

PURPOSE: Retrocochlear pathological findings may be suggested by findings on the brainstem response and acoustic sensorineural reflex (AR) tests. We describe the incidence of acoustic neuroma presenting as sudden hearing loss (SHL) and the effectiveness of the discrimination (DISC) test, the brainstem-evoked response, and AR test in predicting acoustic neuroma in patients with SHL. METHODS: We retrospectively reviewed the charts of all adult patients who presented to our center with sensorineural SHL between 1989 and 1995. Two groups were defined: those with cerebellopontine angle (CPA) tumor and those with negative imaging findings. Results of the brainstem-evoked response, AR, and DISC tests were compared. RESULTS: Forty patients were admitted with sensorineural SHL, of whom 19 (47.5%) had a CPA tumor. The latter group showed a significantly lower mean age and better results for the low frequencies on pure tone audiometry, as well as better brainstem-evoked response test results than the patients with negative imaging findings. There was also a significant difference between the groups for both the affected and unaffected ears on the discrimination test. CONCLUSION: Acoustic tumors may be a more common cause of sudden sensorineural hearing loss than previously suspected. The DISC test is a useful screening tool for acoustic tumor, whereas the brainstem-evoked response test shows poorer results in affected patients with sensorineural hearing loss than in other subgroups with different signs of acoustic neuroma. We recommend that young patients presenting with mild SHL who have normal results on the AR and brainstem-evoked response tests undergo magnetic resonance imaging to rule out CPA tumor.

Evoked Potentials, Auditory, Brain Stem↗

PubMed1983

The acoustic reflex threshold in aging ears.

This study investigates the controversy regarding the influence of age on the acoustic reflex threshold for broadband noise, 500-, 1000-, 2000-, and 4000-Hz activators between Jerger et al. [Mono. Contemp. Audiol. 1 (1978)] and Jerger [J. Acoust. Soc. Am. 66 (1979)] on the one hand and Silman [J. Acoust. Soc. Am. 66 (1979)] and others on the other. The acoustic reflex thresholds for broadband noise, 500-, 1000-, 2000-, and 4000-Hz activators were evaluated under two measurement conditions. Seventy-two normal-hearing ears were drawn from 72 subjects ranging in age from 20-69 years. The results revealed that age was correlated with the acoustic reflex threshold for BBN activator but not for any of the tonal activators; the correlation was stronger under the 1-dB than under the 5-dB measurement condition. Also, the mean acoustic reflex thresholds for broadband noise activator were essentially similar to those reported by Jerger et al. (1978) but differed from those obtained in this study under the 1-dB measurement condition.

Acoustic Stimulation↗

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↗

PubMed1987

Early development of the acoustic reflex.

Acoustic reflex testing was conducted on 2-day-old and on 6-week-old infants to determine how frequently, if at all, the acoustic reflex occurs, if it can be reliably observed, and also to determine what is the mean normal acoustic reflex threshold for pure tones and broad-band noise in these populations. Twenty normal infants were tested in each group. Each infant was considered to be normal by the following criteria: full term, normal pregnancy normal pregnancy and delivery, birth weight greater than 2500 g, 5-min Apgar of 7 or greater, and considered to be not at risk for hearing loss by the absence of any high risk factors. Subjects were tested following feedings. Acoustic reflexes were obtained from subjects with normal tympanograms (+/- 50 mm H2O) for 500, 1,000, 2,000, and 4,000 Hz and broad-band noise stimuli. Behavioral responses were common, requiring quieting pauses in testing and repeated stimulation for habituation of the behavioral component. Acoustic reflexes were observed, and normative reflex threshold data were obtained. The number of reflexes obtained and the mean acoustic reflex thresholds for these age-groups are reported.

Acoustic Impedance Tests↗