Equivalent Sound Pressure Levels of Different Pressure‐Gradient Hydrophones at Low Frequencies due to Turbulent Flow

Several noise propagation models used to calculate the noise produced by wind turbines have been reported. However, these models do not accurately predict sound pressure levels. Most of them have been developed to estimate the noise produced by industries, in which wind speeds are less than 5 m/s, and conditions favor its spread. To date, very few models can be applied to evaluate the propagation of sound from wind turbines and most of these yield inaccurate results. This study presents a comparison between noise levels that were estimated using the prediction method established in ISO 9613 Part 2 and measured levels of noise from wind turbines that are part of a wind farm currently in operation. Differences of up to 56.5 dBZ, with a median of 29.6 dBZ, were found between the estimated sound pressure levels and measured levels. The residual sound pressure levels given by standard ISO 9613 Part 2 for the wind turbines is larger for high frequencies than those for low frequencies. When the wide band equivalent continuous sound pressure level is expressed in dBA, the residual varies between −4.4 dBA and 37.7 dBA, with a median of 20.5 dBA.

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Frequencies Rotation at High Sound Pressure Levels Toward Low Frequencies

Sound&Vibration ◽

10.32604/sv.2020.011086 ◽

2020 ◽

Vol 54 (4) ◽

pp. 237-246

Author(s):

Hadi Negahdari ◽

Sirus Javadpour ◽

Faramarz Moattar

Keyword(s):

Sound Pressure ◽

Low Frequencies ◽

Sound Pressure Levels ◽

High Sound

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The role of compressibility in computing noise generated at a cavitating orifice

International Journal of Aeroacoustics ◽

10.1177/1475472x18812801 ◽

2018 ◽

Vol 18 (1) ◽

pp. 73-91 ◽

Cited By ~ 1

Author(s):

Amir Bashirzadeh Tabrizi ◽

Binxin Wu

Keyword(s):

Mach Number ◽

Flow Field ◽

Sound Pressure ◽

Stokes Equations ◽

Navier Stokes ◽

Physical Situation ◽

Low Frequencies ◽

Sound Pressure Levels ◽

Dynamics Calculation

The computational fluid dynamics calculation can be accomplished by solving either compressible or incompressible Navier–Stokes equations to determine the flow-field variables of the noise source. The proper assumption depends on both the physical situation and the Mach number. Although in cavitating devices usually we are dealing with low Mach number flow, cavitation is an acoustic phenomenon that can be affected by compressibility. Cavitation behaves acoustically as a monopole and it is mentioned by some researchers that incompressible solution is sufficient to study the dipole sources. However, in order to study the monopole (and quadrupole) sources a compressible solution may be required. In this study, the role of compressibility in computing noise generated at a cavitating single-hole orifice was investigated using large eddy simulation and Ffowcs Williams–Hawkings formulation. The fluid zone downstream of the orifice where the cavitation occurs was evaluated as the acoustic source which generates sound. Time-accurate solutions of the flow-field variables on source surfaces were obtained from both compressible and incompressible flow simulations. Three cases of cavitation were studied and the sound pressure signals far downstream of the orifice were computed by the Ffowcs Williams–Hawkings formulation. For a developed cavitation regime at low frequencies, there is a big discrepancy between the computed values of sound pressure level from compressible and incompressible simulations, and at higher frequencies greater than 6 kHz, both simulation methods provide almost the same values for sound pressure levels. For a super cavitation regime, both compressible and incompressible simulations provide similar values for sound pressure levels at frequencies greater than 2 kHz. The results of this work demonstrate that the compressibility has a significant role in terms of computing noise generated at a cavitating orifice and cannot be ignored, especially when the noise generated by developed cavitation regimes at low frequencies is investigated.

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Thresholds and Acceptability of Low Frequency Pure Tones by Sufferers

Journal of Low Frequency Noise Vibration and Active Control ◽

10.1260/026309205775374433 ◽

2005 ◽

Vol 24 (3) ◽

pp. 163-169 ◽

Cited By ~ 5

Author(s):

Yukio Inukai ◽

Hideto Taya ◽

Shinji Yamada

Keyword(s):

Sound Pressure ◽

Low Frequency ◽

Psychophysical Method ◽

Psychophysical Experiment ◽

Living Room ◽

Sensory Thresholds ◽

Low Frequencies ◽

Sound Pressure Levels ◽

Measurement Experiment ◽

Pure Tones

In order to investigate sensory thresholds and to make subjective evaluations of low frequency pure tones in noise sufferers who complain of annoying environments in their everyday life, sound pressure levels of sensory thresholds and subjectively acceptable maximum SPL levels for a living room were measured in a low frequency chamber. These measurements involved a psychophysical experiment using eleven pure tones at low frequencies from 10Hz to 100 Hz as stimuli, and the psychophysical method of subject adjustment was used for the measurements. Twelve members of the noise-sufferer's society in Japan participated as subjects (referred to as participants in the measurement experiment). The results show that all the participants' acceptable maximum sound pressure levels were relatively low, and nearly equal to their sensory thresholds. These results are characteristic of the participants and differ from the previous results obtained from the other adults.

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

American Journal of Audiology ◽

10.1044/1059-0889.0104.52 ◽

1992 ◽

Vol 1 (4) ◽

pp. 52-55 ◽

Cited By ~ 4

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.

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

Journal of Speech Language and Hearing Research ◽

10.1044/2020_jslhr-19-00053 ◽

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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