Shear layer effects on pure tone sound propagation in open jet wind tunnels using 1/3 octave analysis

1980 ◽  
Author(s):  
R. ROSS
Keyword(s):  
Shear Layer ◽  
Pure Tone ◽  
Sound Propagation ◽  
Wind Tunnels

Application of an inner expansion method to plane, inviscid, compressible flow stability studies

1974 ◽  
Vol 62 (2) ◽  
pp. 405-416 ◽  
Author(s):  
Roy J. Beckemeyer
Keyword(s):  
Shear Layer ◽  
Compressible Flow ◽  
Sound Propagation ◽  
Expansion Method ◽  
Shear Layers ◽  
Flow Stability ◽  
Mean Flow ◽  
Finite Shear ◽  
Flow Profiles ◽  
Inviscid Compressible Flow

The inviscid compressible flow stability problem is mathematically similar to that of sound propagation in a sheared flow field. This similarity has been exploited by applying an inner expansion technique to study the effect of finite shear gradients on free parallel flow instabilities. This technique had previously been used to investigate the effect of thin boundary layers on sound propagation in ducts. The expansion, which is applicable to flow profiles involving thin, but finite, shear layers separating regions of uniform flow, offers a significant computational advantage over the numerical methods commonly employed to determine the stability of continuous mean flow profiles. Although equally applicable to three-dimensional and to spatially growing hydrodynamic instabilities, the procedure is demonstrated by application to the eigenvalue problem for temporal instabilities of shear layers and jets in plane inviscid compressible flow.For the case of vanishingly thin shear layers, the eigenvalue equations derived here reduce to those obtained by Miles (1958) for parallel flows bounded by vortex sheets. The series solution of Graham & Graham (1969), valid for linear shear-layer profiles of arbitrary thickness, provides a basis of comparison for the expansion-method results. Unstable-mode eigenvalues obtained using the two methods are found to be in good agreement for a significant range of values of the ratio of shear-layer thickness to axial wavelength.

Practical considerations for ray casting shear layer corrections

2021 ◽  
pp. 1475472X2110526
Author(s):  
Todd Schultz
Keyword(s):  
Shear Layer ◽  
Ray Tracing ◽  
Acoustic Waves ◽  
Phased Arrays ◽  
Acoustic Propagation ◽  
Wind Tunnels ◽  
Computational Time ◽  
Propagation Time ◽  
Ray Casting ◽  
Casting Method

Aircraft noise reduction technology development has been aided by the use of acoustic phased arrays to identify component-level locations of noise sources. Acoustic phased arrays are commonly used in both closed-wall and open-jet wind tunnels, thus requiring accurate acoustic propagation models to focus the array. In particular, open-jet wind tunnels have complex flow fields including a free shear layer that the acoustic waves must propagate through. A method using ray tracing is reviewed and an enhancement proposed to reduce the computational time for cases requiring a large number of rays. The proposed reduced ray casting method uses ray tracing to the extreme edges of the region of interest and limits all casted acoustic rays to within that region. The results showed that a hemispherical spiral discretization had lower error in the estimated acoustic propagation time than uniform angular discretization. The proposed reduced ray casting method showed similar accuracy as the original ray casting method but with improvement in the computational times when the number of cast rays was greater than 3200 as needed for modeling acoustic propagation in larger industrial sized open-jet wind tunnels.

Real-ear Masking Calibration for Portable Pure-Tone Audiometers

1984 ◽  
Vol 15 (4) ◽  
pp. 289-294
Author(s):  
Martin S. Robinette ◽  
Robert H. Brey
Keyword(s):  
Pure Tone ◽  
Broad Band ◽  
Resistive Network ◽  
Many Instruments

A transformer mixing network is described which allows the calibration of broad-band masking for portable audiometers that lack a built-in mixing network. For many instruments the transformer network is preferable to the resistive network previously published.

Misophonia: An Evidence-Based Case Report

2020 ◽  
Vol 29 (4) ◽  
pp. 685-690
Author(s):  
C. S. Vanaja ◽  
Miriam Soni Abigail
Keyword(s):  
Quality Of Life ◽  
Case Report ◽  
Case History ◽  
Pure Tone ◽  
Physiological Responses ◽  
Evidence Based ◽  
Management Option ◽  
Pure Tone Audiogram

Purpose Misophonia is a sound tolerance disorder condition in certain sounds that trigger intense emotional or physiological responses. While some persons may experience misophonia, a few patients suffer from misophonia. However, there is a dearth of literature on audiological assessment and management of persons with misophonia. The purpose of this report is to discuss the assessment of misophonia and highlight the management option that helped a patient with misophonia. Method A case study of a 26-year-old woman with the complaint of decreased tolerance to specific sounds affecting quality of life is reported. Audiological assessment differentiated misophonia from hyperacusis. Management included retraining counseling as well as desensitization and habituation therapy based on the principles described by P. J. Jastreboff and Jastreboff (2014). A misophonia questionnaire was administered at regular intervals to monitor the effectiveness of therapy. Results A detailed case history and audiological evaluations including pure-tone audiogram and Johnson Hyperacusis Index revealed the presence of misophonia. The patient benefitted from intervention, and the scores of the misophonia questionnaire indicated a decrease in the severity of the problem. Conclusions It is important to differentially diagnose misophonia and hyperacusis in persons with sound tolerance disorders. Retraining counseling as well as desensitization and habituation therapy can help patients who suffer from misophonia.

Evaluation of Efferent Auditory System and Hearing Quality in Parkinson's Disease: Is the Difficulty in Speech Understanding in Complex Listening Conditions Related to Neural Degeneration or Aging?

2020 ◽  
pp. 1-9
Author(s):  
Nuriye Yıldırım Gökay ◽  
Bülent Gündüz ◽  
Fatih Söke ◽  
Recep Karamert
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Auditory System ◽  
Otoacoustic Emissions ◽  
Pure Tone ◽  
Pure Tone Audiometry ◽  
Auditory Pathway ◽  
Normal Hearing ◽  
System Function ◽  
Distortion Product

Purpose The effects of neurological diseases on the auditory system have been a notable issue for investigators because the auditory pathway is closely associated with neural systems. The purposes of this study are to evaluate the efferent auditory system function and hearing quality in Parkinson's disease (PD) and to compare the findings with age-matched individuals without PD to present a perspective on aging. Method The study included 35 individuals with PD (mean age of 48.50 ± 8.00 years) and 35 normal-hearing peers (mean age of 49 ± 10 years). The following tests were administered for all participants: the first section of the Speech, Spatial and Qualities of Hearing Scale; pure-tone audiometry, speech audiometry, tympanometry, and acoustic reflexes; and distortion product otoacoustic emissions (DPOAEs) and contralateral suppression of DPOAEs. SPSS Version 25 was used for statistical analyses, and values of p < .05 were considered statistically significant. Results There were no statistically significant differences in the pure-tone audiometry thresholds and DPOAE responses between the individuals with PD and their normal-hearing peers ( p = .732). However, statistically significant differences were found between the groups in suppression levels of DPOAEs and hearing quality ( p < .05). In addition, a statistically significant and positive correlation was found between the amount of suppression at some frequencies and the Speech, Spatial and Qualities of Hearing Scale scores. Conclusions This study indicates that medial olivocochlear efferent system function and the hearing quality of individuals with PD were affected adversely due to the results of PD pathophysiology on the hearing system. For optimal intervention and follow-up, tasks related to hearing quality in daily life can also be added to therapies for PD.

Factors Influencing Electrophysiologic Responsivity in Normal Adults

1965 ◽  
Vol 8 (4) ◽  
pp. 323-347
Author(s):  
Robert Goldstein ◽  
Benjamin RosenblÜt
Keyword(s):  
Conditioned Stimulus ◽  
White Light ◽  
Pure Tone ◽  
Alpha Rhythm ◽  
White Women ◽  
White Men ◽  
Inverse Relation ◽  
Factors Influencing ◽  
Electrodermal Responses ◽  
Normal Adults

Electrodermal and electroencephalic responsivity to sound and to light was studied in 96 normal-hearing adults in three separate sessions. The subjects were subdivided into equal groups of white men, white women, colored men, and colored women. A 1 000 cps pure tone was the conditioned stimulus in two sessions and white light was used in a third session. Heat was the unconditioned stimulus in all sessions. Previously, an inverse relation had been found in white men between the prominence of alpha rhythm in the EEG and the ease with which electrodermal responses could be elicited. This relation did not hold true for white women. The main purpose of the present study was to answer the following questions: (1) are the previous findings on white subjects applicable to colored subjects? (2) are subjects who are most (or least) responsive electrophysiologically on one day equally responsive (or unresponsive) on another day? and (3) are subjects who are most (or least) responsive to sound equally responsive (or unresponsive) to light? In general, each question was answered affirmatively. Other factors influencing responsivity were also studied.

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