Noise Transmission Through a Vehicle Side Window Due to Turbulent Boundary Layer Excitation

1997 ◽  
Vol 119 (4) ◽  
pp. 557-562 ◽  
Author(s):  
S. F. Wu ◽  
G. Wu ◽  
M. M. Puskarz ◽  
M. E. Gleason
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Random Vibration ◽  
Sound Pressure ◽  
Side Window ◽  
Reverberation Chamber ◽  
Vibration Excitation ◽  
Sound Pressure Levels ◽  
Noise Transmission ◽  
Acoustic Absorption Coefficient

This paper presents results of an investigation on noise transmission through an aluminum panel clamped to a greenhouse vehicle model subject to random acoustics, random vibration, and turbulent boundary layer excitations. Experiments on random acoustics and random vibration excitations were carried out in a reverberation chamber, and those on turbulent boundary layer excitation were conducted in the wind tunnel at the Chrysler Technology Center. The transmitted noise spectra were also calculated using a single computer program VibroAcoustic Payload Environment Prediction System (VAPEPS) based on Statistic Energy Analysis (SEA). The acoustic absorption coefficient (AAC) and the damping loss factor (DLF) for the vehicle were determined based on experimental data. Results showed that the largest differences between the measured and calculated sound pressure levels in any frequency band above 500 Hz were less than 2.5 dB for random acoustics excitation, 5.0 dB for random vibration excitation, and 5 dB for turbulent boundary layer excitation. In spite of the presence of differences in individual frequency bands, the calculated total sound pressure levels compared well with the measured ones. The differences between the calculated and measured total sound pressure levels were 0.7 dB for random acoustics excitation, 0.4 dB for random vibration excitation, and 1.8 dB for turbulent boundary layer excitation.

scholarly journals Prediction of Turbulent Boundary Layer Induced Noise in the Cabin of a BWB Aircraft

2012 ◽  
Vol 19 (4) ◽  
pp. 693-705 ◽  
Author(s):  
Joana Rocha ◽  
Afzal Suleman ◽  
Fernando Lau
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Sound Pressure ◽  
Pressure Level ◽  
Interior Noise ◽  
Analytical Models ◽  
Frequency Range ◽  
Noise Levels ◽  
Cabin Noise ◽  
Cabin Interior

This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). While, in previous works, the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is analyzed. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabin of a Blended Wing Body (BWB) aircraft, for the frequency range 0–1000 Hz. The results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. Additionally, the model is able to predict local SPL values, at specific locations in the cabin, which are also affected with by number of vibrating panels, and are different from the average values.

scholarly journals The Effect of Angle of Attack and Flow Conditions on Turbulent Boundary Layer Noise of Small Wind Turbines

2017 ◽  
Vol 42 (1) ◽  
pp. 83-91
Author(s):  
Nadiia Afanasieva
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Wind Turbines ◽  
Sound Pressure ◽  
Angle Of Attack ◽  
Noise Spectrum ◽  
Acoustic Spectrum ◽  
Small Wind Turbines ◽  
Local Angle ◽  
Broadband Frequency

Abstract The article aims to solve the problem of noise optimization of small wind turbines. The detailed analysis concentrates on accurate specification and prediction of the turbulent boundary layer noise spectrum of the blade airfoil. The angles of attack prediction for a horizontal axis wind turbine (HAWT) and the estimation based on literature data for a vertical axis one (VAWT), were conducted, and the influence on the noise spectrum was considered. The 1/3-octave sound pressure levels are obtained by semi-empirical model BPM. Resulting contour plots show a fundamental difference in the spectrum of HAWT and VAWT reflecting the two aerodynamic modes of flow that predefine the airfoil self-noise. Comparing the blade elements with a local radius of 0.875 m in the HAWT and VAWT conditions the predicted sound pressure levels are the 78.5 dB and 89.8 dB respectively. In case of the HAWT with predicted local angle of attack ranging from 2.98° to 4.63°, the acoustic spectrum will vary primarily within broadband frequency band 1.74-20 kHz. For the VAWT with the local angle of attack ranging from 4° to 20° the acoustic spectrum varies within low and broadband frequency bands 2 Hz - 20 kHz.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Personal Audio System: Hearing Symptoms, Habits, and Sound Pressure Levels Measured in Real Ear and a Manikin

2020 ◽  
Vol 63 (6) ◽  
pp. 2016-2026
Author(s):  
Tamara R. Almeida ◽  
Clayton H. Rocha ◽  
Camila M. Rabelo ◽  
Raquel F. Gomes ◽  
Ivone F. Neves-Lobo ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Daily Basis ◽  
Cross Sectional Study ◽  
Normal Hearing ◽  
Chi Square ◽  
Cross Sectional ◽  
The Real ◽  
Significant Difference ◽  
Sound Pressure Levels ◽  
Audio System

Purpose The aims of this study were to characterize hearing symptoms, habits, and sound pressure levels (SPLs) of personal audio system (PAS) used by young adults; estimate the risk of developing hearing loss and assess whether instructions given to users led to behavioral changes; and propose recommendations for PAS users. Method A cross-sectional study was performed in 50 subjects with normal hearing. Procedures included questionnaire and measurement of PAS SPLs (real ear and manikin) through the users' own headphones and devices while they listened to four songs. After 1 year, 30 subjects answered questions about their usage habits. For the statistical analysis, one-way analysis of variance, Tukey's post hoc test, Lin and Spearman coefficients, the chi-square test, and logistic regression were used. Results Most subjects listened to music every day, usually in noisy environments. Sixty percent of the subjects reported hearing symptoms after using a PAS. Substantial variability in the equivalent music listening level (Leq) was noted ( M = 84.7 dBA; min = 65.1 dBA, max = 97.5 dBA). A significant difference was found only in the 4-kHz band when comparing the real-ear and manikin techniques. Based on the Leq, 38% of the individuals exceeded the maximum daily time allowance. Comparison of the subjects according to the maximum allowed daily exposure time revealed a higher number of hearing complaints from people with greater exposure. After 1 year, 43% of the subjects reduced their usage time, and 70% reduced the volume. A volume not exceeding 80% was recommended, and at this volume, the maximum usage time should be 160 min. Conclusions The habit of listening to music at high intensities on a daily basis seems to cause hearing symptoms, even in individuals with normal hearing. The real-ear and manikin techniques produced similar results. Providing instructions on this topic combined with measuring PAS SPLs may be an appropriate strategy for raising the awareness of people who are at risk. Supplemental Material https://doi.org/10.23641/asha.12431435

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