The Relationship Between Truck Tire Vibration and Near and Far Field Sound Levels

1976 ◽  
Author(s):  
W. F. Reiter ◽  
A. C. Eberhardt
Keyword(s):  
Far Field ◽  
Sound Levels ◽  
Truck Tire ◽  
The Relationship ◽  
Field Sound

scholarly journals Impact of coherence decay on wavepacket models for broadband shock-associated noise in supersonic jets

2019 ◽  
Vol 863 ◽  
pp. 969-993 ◽  
Author(s):  
Marcus H. Wong ◽  
Peter Jordan ◽  
Damon R. Honnery ◽  
Daniel Edgington-Mitchell
Keyword(s):  
Dynamic Models ◽  
Critical Role ◽  
Coherence Function ◽  
Supersonic Jets ◽  
Far Field ◽  
Shock Cell ◽  
Acoustic Spectrum ◽  
Flow Mechanisms ◽  
The Relationship ◽  
Field Sound

Motivated by the success of wavepackets in modelling the noise from subsonic and perfectly expanded supersonic jets, we apply the wavepacket model to imperfectly expanded supersonic jets. Recent studies with subsonic jets have demonstrated the importance of capturing the ‘jitter’ of wavepackets in order to correctly predict the intensity of far-field sound. Wavepacket jitter may be statistically represented using a two-point coherence function; accurate prediction of noise requires identification of this coherence function. Following the analysis of Cavalieri & Agarwal (J. Fluid Mech., vol. 748, 2014. pp. 399–415), we extend their methodology to model the acoustic sources of broadband shock-associated noise in imperfectly expanded supersonic jets using cross-spectral densities of the turbulent and shock-cell quantities. The aim is to determine the relationship between wavepacket coherence-decay and far-field broadband shock-associated noise, using the model as a vehicle to explore the flow mechanisms at work. Unlike the subsonic case where inclusion of coherence decay amplifies the sound pressure level over the whole acoustic spectrum, we find that it does not play such a critical role in determining the peak sound amplitude for shock-cell noise. When higher-order shock-cell modes are used to reconstruct the acoustic spectrum at higher frequencies, however, the inclusion of a jittering wavepacket is necessary. These results suggest that the requirement for coherence decay identified in prior broadband shock-associated noise (BBSAN) models is in reality the statistical signature of jittering wavepackets. The results from this modelling approach suggest that nonlinear jittering effects of wavepackets need to be included in dynamic models for broadband shock-associated noise.

scholarly journals Snoring: a source of noise pollution and sleep apnea predictor

SLEEP ◽  
2019 ◽  
Vol 43 (6) ◽  
Author(s):  
Mudiaga Sowho ◽  
Francis Sgambati ◽  
Michelle Guzman ◽  
Hartmut Schneider ◽  
Alan Schwartz
Keyword(s):  
Sleep Apnea ◽  
Operating Characteristic ◽  
Area Under The Curve ◽  
Noise Pollution ◽  
Apnea Hypopnea Index ◽  
Sleep Study ◽  
Sound Levels ◽  
Obstructive Sleep ◽  
Single Night ◽  
The Relationship

Abstract Snoring is a highly prevalent condition associated with obstructive sleep apnea (OSA) and sleep disturbance in bed partners. Objective measurements of snoring in the community, however, are limited. The present study was designed to measure sound levels produced by self-reported habitual snorers in a single night. Snorers were excluded if they reported nocturnal gasping or had severe obesity (BMI > 35 kg/m2). Sound was measured by a monitor mounted 65 cm over the head of the bed on an overnight sleep study. Snoring was defined as sound ≥40 dB(A) during flow limited inspirations. The apnea hypopnea index (AHI) and breath-by-breath peak decibel levels were measured. Snore breaths were tallied to determine the frequency and intensity of snoring. Regression models were used to determine the relationship between objective measures of snoring and OSA (AHI ≥ 5 events/h). The area under the curve (AUC) for the receiver operating characteristic (ROC) was used to predict OSA. Snoring intensity exceeded 45 dB(A) in 66% of the 162 participants studied, with 14% surpassing the 53 dB(A) threshold for noise pollution. Snoring intensity and frequency were independent predictors of OSA. AUCs for snoring intensity and frequency were 77% and 81%, respectively, and increased to 87% and 89%, respectively, with the addition of age and sex as predictors. Snoring represents a source of noise pollution in the bedroom and constitutes an important target for mitigating sound and its adverse effects on bed partners. Precise breath-by-breath identification and quantification of snoring also offers a way to risk stratify otherwise healthy snorers for OSA.

scholarly journals Structural and Acoustic Responses of a Submerged Stiffened Conical Shell

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Meixia Chen ◽  
Cong Zhang ◽  
Xiangfan Tao ◽  
Naiqi Deng
Keyword(s):  
Conical Shell ◽  
Element Model ◽  
Analytical Models ◽  
Superposition Method ◽  
Far Field ◽  
Fluid Loading ◽  
Low Frequencies ◽  
Structural Responses ◽  
The Individual ◽  
Field Sound

This paper studies the vibrational behavior and far-field sound radiation of a submerged stiffened conical shell at low frequencies. The solution for the dynamic response of the conical shell is presented in the form of a power series. A smeared approach is used to model the ring stiffeners. Fluid loading is taken into account by dividing the conical shell into narrow strips which are considered to be local cylindrical shells. The far-field sound pressure is solved by the Element Radiation Superposition Method. Excitations in two directions are considered to simulate the loading on the surface of the conical shell. These excitations are applied along the generator and normal to the surface of the conical shell. The contributions from the individual circumferential modes on the structural responses of the conical shell are studied. The effects of the external fluid loading and stiffeners are discussed. The results from the analytical models are validated by numerical results from a fully coupled finite element/boundary element model.

Ground Attenuation Factor Based on Measurements

2021 ◽  
Vol 263 (3) ◽  
pp. 3436-3447
Author(s):  
Dan Lin ◽  
Andrew Eng
Keyword(s):  
Near Field ◽  
Attenuation Factor ◽  
Measurement Data ◽  
Low Frequency ◽  
Sound Sources ◽  
Frequency Sound ◽  
Sound Levels ◽  
Different Types ◽  
Noise Measurements ◽  
Field Sound

Assumptions made on the ground types between sound sources and receivers can significantly impact the accuracy of environmental outdoor noise prediction. A guideline is provided in ISO 9613-2 and the value of ground factor ranges from 0 to 1, depending on the coverage of porous ground. For example, a ground absorption factor of 1 is suggested for grass ground covers. However, it is unclear if the suggested values are validated. The purpose of this study is to determine the sound absorption of different types of ground by measurements. Field noise measurements were made using an omnidirectional loudspeaker and two microphones on three different types of ground in a quiet neighborhood. One microphone was located 3ft from the loudspeaker to record near field sound levels in 1/3 and 1 octave bands every second. The other microphone was located a few hundred feet away to record far field sound in the same fashion as the near field microphone. The types of ground tested were concrete, grass, and grass with trees. Based on the measurement data, it was found that grass and trees absorb high frequency sound well and a ground factor of 1 may be used for 500Hz and up when using ISO 9613-2 methodology. However, at lower frequencies (125 Hz octave band and below), grassy ground reflects sound the same as concrete surfaces. Trees absorb more low frequency sound than grass, but less than ISO 9613-2 suggested.

Compact acoustic metalens with sinusoidal sub-channels for directional far-field sound beams

2019 ◽  
Vol 12 (8) ◽  
pp. 087002
Author(s):  
Fuxi Zhang ◽  
Edmon Perkins ◽  
Shiming Wang ◽  
George T. Flowers ◽  
Robert N. Dean
Keyword(s):  
Far Field ◽  
Sound Beams ◽  
Field Sound

Attenuation Function Relationship for Far Field Earthquake Considered by Strike Slip Mechanism

2015 ◽  
Vol 754-755 ◽  
pp. 897-901
Author(s):  
Saffuan Wan Ahmad ◽  
Azlan Adnan ◽  
Rozaimi Mohd Noor ◽  
Khairunisa Muthusamy ◽  
Sk Muiz Sk Razak ◽  
...  
Keyword(s):  
Peak Ground Acceleration ◽  
Strike Slip ◽  
Far Field ◽  
Attenuation Relationship ◽  
Ground Acceleration ◽  
Slip Mechanism ◽  
Earthquake Sources ◽  
Peak Ground Accelerations ◽  
Function Relationship ◽  
The Relationship

An attenuation relationship for far field earthquakes considered by strike slip has been developed. The attenuation relationship function was develop using regression analysis. The database consisting of more than 130 peak ground accelerations from seven earthquake sources recorded by Seismology Station in Malaysia have been used to develop the relationship. This study aims to investigate the new relationship attenuation to gain exact peak ground acceleration at the location on site. Based on this study, the location is a structure located at Terengganu seaside.

On-axis and far-field sound radiation from resilient flat and dome-shaped radiators

2009 ◽  
Vol 125 (3) ◽  
pp. 1444-1455 ◽  
Author(s):  
Ronald M. Aarts ◽  
Augustus J. E. M. Janssen
Keyword(s):  
Sound Radiation ◽  
Far Field ◽  
Field Sound
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