Passive subtractive beamformer for near-field sound sources

2005 ◽  
Author(s):  
M. Mizumachi ◽  
S. Nakamura
Keyword(s):  
Near Field ◽  
Sound Sources ◽  
Near Field Sound ◽  
Field Sound

Passive hybrid subtractive beamformer for near-field sound sources

2005 ◽  
Vol 26 (6) ◽  
pp. 495-501
Author(s):  
Mitsunori Mizumachi ◽  
Satoshi Nakamura
Keyword(s):  
Near Field ◽  
Sound Sources ◽  
Near Field Sound ◽  
Field Sound

Hydrodynamic Noise and Radiated Mechanism of 3D Cavity

2012 ◽  
Vol 217-219 ◽  
pp. 2590-2593 ◽  
Author(s):  
Yu Wang ◽  
Bai Zhou Li
Keyword(s):  
Sound Pressure ◽  
Near Field ◽  
Low Frequency ◽  
Dipole Source ◽  
Fluctuating Pressure ◽  
Common Structure ◽  
Hydrodynamic Noise ◽  
Near Field Sound ◽  
Equivalent Sources ◽  
Field Sound

The flow past 3D rigid cavity is a common structure on the surface of the underwater vehicle. The hydrodynamic noise generated by the structure has attracted considerable attention in recent years. Based on LES-Lighthill equivalent sources method, a 3D cavity is analyzed in this paper, when the Mach number is 0.0048. The hydrodynamic noise and the radiated mechanism of 3D cavity are investigated from the correlation between fluctuating pressure and frequency, the near-field sound pressure intensity, and the propagation directivity. It is found that the hydrodynamic noise is supported by the low frequency range, and fluctuating pressure of the trailing-edge is the largest, which is the main dipole source.

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.

A study of brake disc modal behaviour during squeal generation using high-speed electronic speckle pattern interferometry and near-field sound pressure measurements

2000 ◽  
Vol 214 (3) ◽  
pp. 285-296 ◽  
Author(s):  
M Reeves ◽  
N Taylor ◽  
C Edwards ◽  
D Williams ◽  
C. H. Buckberry
Keyword(s):  
High Speed ◽  
Sound Pressure ◽  
Surface Deformation ◽  
Speckle Pattern ◽  
Near Field ◽  
Electronic Speckle Pattern Interferometry ◽  
Brake Disc ◽  
Pressure Measurements ◽  
Near Field Sound ◽  
Field Sound

The out-of-plane surface vibration of a brake disc during naturally excited squeal has been investigated using a combination of high-speed electronic speckle pattern interferometry (ESPI) and near-field sound pressure measurements. Both techniques provide visualization and quantification of the time-resolved surface velocity. A mathematical description of disc brake squeal modal behaviour is proposed that predicts accurately all of the experimentally observed interferometry and sound field measurements. The complex mode description proposed here is in agreement with that proposed by others for drum brake squeal. This assumes that two identical diametral modes are excited simultaneously, identical except for a spatial and temporal phase shift. The use of a near-field microphone array provided a convenient multipoint, non-contacting vibration probe which may find use in the study of other vibrations characterized by high surface amplitudes and efficient sound radiation. The high-speed ESPI provided a real-time visualization of surface deformation analogous to double- pulsed holographic interferometry, with the benefit of giving a true time series of the surface deformation during a single vibration cycle.

An Experimental Investigation on the Bridge Effect in Sound Produced by Setar

2009 ◽  
Author(s):  
Hossein Mansour ◽  
Siamak Arzanpour ◽  
Hedayat Alghassi ◽  
Mehdi Behzad
Keyword(s):  
Experimental Investigation ◽  
Near Field ◽  
Musical Instruments ◽  
Minor Effect ◽  
The Third ◽  
Vibrating System ◽  
Novel Approach ◽  
Energy Transfers ◽  
Near Field Sound ◽  
Field Sound

This study aims to evaluate the amount of energy transfers through the bridge in Setar, a Persian long-necked lute. Stringed musical instruments are among the most complicated acoustical systems. When the string is plucked, its vibration distributes into the entire vibrating system (i.e. body, string, air enclosure) and produces sound. The resultant sound consists of three parts: the first is the string’s direct sound; the second is that part of sound-box vibration being excited by string’s direct sound, and the third is the part of sound-box vibration being excited by string force passing through bridge. The last part believed to have the major share and the others have minor effect. For this research, a specific fixture has been made and a precise plucking machine is installed to hold and pluck the instrument uniformly. Also, a novel approach is utilized to evaluate the share of each abovementioned part in the output near-field sound produced by Setar.

scholarly journals Near-field sound radiation of fan tones from an installed turbofan aero-engine

2015 ◽  
Vol 138 (3) ◽  
pp. 1313-1324 ◽  
Author(s):  
Alan McAlpine ◽  
James Gaffney ◽  
Michael J. Kingan
Keyword(s):  
Near Field ◽  
Sound Radiation ◽  
Aero Engine ◽  
Near Field Sound ◽  
Field Sound

Estimation of Plate Vibration and Its Far Field Sound by Means of Near Field Sound Measurement

1986 ◽  
Vol 29 (252) ◽  
pp. 1874-1880 ◽  
Author(s):  
Kiyohiko UMEZAWA ◽  
Haruo HOUJOH ◽  
Tadashi KITANO
Keyword(s):  
Near Field ◽  
Plate Vibration ◽  
Far Field ◽  
Sound Measurement ◽  
Near Field Sound ◽  
Field Sound
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