Extracting engine noise source levels from phased arrays with improved internal source models and evaluation against simulated and measured data

2012 ◽  
Author(s):  
Brian Tester ◽  
Tiphaine Recoup ◽  
Gwenael Gabard
Keyword(s):  
Phased Arrays ◽  
Noise Source ◽  
Measured Data ◽  
Internal Source ◽  
Engine Noise ◽  
Source Models

Acoustic Double Holography Method and its Application to Engine Noise Research

1997 ◽  
Author(s):  
Milsuo Nakano ◽  
Masao Nagamatsu ◽  
Kohei Suzuki ◽  
Takuya Yoshimura
Keyword(s):  
Noise Source ◽  
Near Field ◽  
Wave Length ◽  
Pressure Data ◽  
Acoustic Holography ◽  
Engine Noise ◽  
Simplified Approach ◽  
Noise Shielding ◽  
Full Load Operation ◽  
Control Work

Abstract The acoustic holography (AH) method with single measuring plane has been well known as the conventional method and can be implemented by far field measurement with simple instruments. However, the noise source resolution of the AH is not sufficient. In order to improve the resolution in the noise source identification, several kinds of the acoustic holography methods have been so far proposed. For example, the near field acoustic holography (NAH) can provide high and accurate resolution of the holography by the nearfield measurement. However, the nearfield measurement within one wave length is sometimes impossible in the actual circumstances. The Acoustic Double Holography (A D H) proposed in this paper is a simplified approach with higher resolution of the noise source locations than that of the conventional AH methods. The ADH method basically uses dual measuring planes and does not require nearfield measurement. The sound pressure data detected on the rear plane are transformed into the virtual pressure data on the front plane taking into account of the distance between the plane and the object. Comparing the virtual pressure data with the actual data measured on the front plane, resolution on holography can be improved significantly. Computer simulation and an experiment with two loud speakers were executed in order to confirm the fundamental feature of the proposed method. Several advantages on the method with respect to resolution over the conventional AH method were discussed. Furthermore, the ADH measurement was carried out on running engine under the full load operation. Through these results, the highly noise radiating areas on the engine surface were detected and reduced with noise shielding material. The overall engine noise level was reduced by 1.5dBA as the first stage in this noise control work.

Noise source models for fricative consonants

2000 ◽  
Vol 8 (3) ◽  
pp. 328-344 ◽  
Author(s):  
S. Narayanan ◽  
A. Alwan
Keyword(s):  
Noise Source ◽  
Source Models

The Prediction of Airflow Generated Noise in Ventilation Systems

1997 ◽  
Vol 4 (4) ◽  
pp. 275-294 ◽  
Author(s):  
C.M. Mak ◽  
D.C. Waddington ◽  
D.J. Oldham
Keyword(s):  
Data Collection ◽  
Large Scale ◽  
Noise Source ◽  
Ventilation System ◽  
Measured Data ◽  
Accurate Prediction ◽  
Long Period ◽  
Large Scale Data ◽  
Scale Data ◽  
Ventilation Systems

At long distances from the primary noise source (the fan) of a ventilation system, airflow generated noise from duct fittings can become the major noise problem. There exists only a limited amount of measured data on flow generated noise produced by some in-duct elements such as bends and transition pieces. This lack of data reflects the difficulty in obtaining such information from conventional measurements techniques. As an alternative to large scale data collection, attempts have been made to develop pressure-based techniques for predicting the flow generated noise in a duct. In this paper it is shown that the work of a number of investigators over a long period of time has resulted in the development of techniques for the accurate prediction of flow generated noise due to duct components.

Modified Shielding Jet Model for Twin-Jet Shielding Analysis

1984 ◽  
Vol 106 (3) ◽  
pp. 421-426
Author(s):  
C. H. Gerhold ◽  
J. Gilbride
Keyword(s):  
Cross Section ◽  
Slug Flow ◽  
Noise Source ◽  
Model Development ◽  
Realistic Model ◽  
Measured Data ◽  
Air Jet ◽  
Constant Radius ◽  
Flow Approximation ◽  
Subsonic Jet

An analytical model to estimate the shielding of noise emitted from a point noise source has been developed assuming the shielding jet to be a cylinder of constant radius with uniform flow across the cross section. Comparison to experiment indicated that the model overestimates diffraction of sound around the jet in the far downstream region. The shielding jet model is modified to include widening downstream of the nozzle exit. This not only represents a more realistic model of the jet, but is also expected to improve the shielding estimate downstream. The modified jet model incorporates a Mach number dependent widening rate, a corresponding decrease in flow velocity downstream and an equivalent slug flow evaluation to retain the locally parallel flow approximation of the model development. The shielding analysis with modified jet model is compared to measured data for a subsonic isothermal air jet and a simulated hot subsonic jet. Improvement of the shielding estimate is discussed.

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