Observations on the Systematic Deviations between Two Methods of Measuring Sound Transmission Loss

1996 ◽  
Vol 3 (1) ◽  
pp. 1-11 ◽  
Author(s):  
F. Jacobsen ◽  
H. Ding

The paper examines and discusses possible explanations of the systematic deviations between conventional and intensity-based sound transmission loss measurements frequently reported in the literature. Both the conventional diffuse-field method and the method based on the sound intensity technique are subject to several systematic errors of comparable size. The sources of error include non-linear decay functions, the absorption of the partition itself, and intensity measurement errors, which are aggravated by the fact that the sound field conditions are usually fairly difficult. It is concluded that with very careful measurement procedures there are no systematic deviations.

2021 ◽  
Vol 263 (5) ◽  
pp. 1539-1547
Author(s):  
Xiaolong LI ◽  
Shiu Keung Tang ◽  
Shiu-Keung, Tang

In present study, a 1:4 scaled down model was used to explore the noise reduction across the plenum window with add-in dual staggered scatterer arrays (sonic-crystal). Reverberation time inside the model space was measured firstly to eliminate the effect of the possible reverberation variation on the sound transmission loss of the plenum window. Two sonic-crystal arrays, the two-by-two and two-by-three scatterer arrangements, were adopted for measurement. A total of four arrays was thus tested after the staggering. Computational simulation was conducted for the sound field inside the plenum chamber to study the noise reduction mechanism of the present window system. Results show that the noise reduction of the plenum window was improved by varying degrees due to the placement of the dual staggered sonic-crystal. The Installation of the dual staggered sonic-crystal increased the sound energy reflections out of the plenum window inlet and decreased the sound energy that passed through the plenum window cavity. At the same time, the resonances inside the window cavity also contributed to the sound transmission loss of the plenum window. The noise reduction across the plenum window was enhanced. The improvement was between ~2 to ~2.7 dBA.


2001 ◽  
Vol 8 (1) ◽  
pp. 41-56 ◽  
Author(s):  
K. T. Chen ◽  
S. H. Jan

A study is reported of the sound transmission loss of perforated panels. The study includes a theoretical analysis and measurement by means of sound intensity. The predicted transmission loss is similar to that measured above 630 Hz. The maximum discrepancy is less than 2 dB. The perforation in a thick panel is found to reduce the coincidence effect at the critical frequency.


2013 ◽  
Vol 380-384 ◽  
pp. 73-76
Author(s):  
Xiu Feng Wang ◽  
Jie Shi

The sound transmission loss (STL) of the acoustic parts in the vehicle was proposed to be computed using the Sound Pressure Level measured at the several locations inside the vehicle and the transmitted Sound Intensity Level on the vehicles exterior panel, which the acoustic treated vehicle passenger compartment is assumed as a small reverberation room. The necessary parts retrofits and acoustic treatments for Sound transmission loss tests of the acoustic parts in the vehicle were listed. The values of the appropriate number and positions of the loud speakers, microphones and sound intensity probes for Sound transmission loss of the acoustic parts in the vehicle were recommended. The in vehicle sound transmission loss tests of the acoustic parts such as the doors, carpets, wheel house etc. were achieved in the semi-anechoic room. Based on the door system, the correlation work has been done among the methods of the proposed in vehicle STL test, the reverberation - semi-anechoic chamber buck STL test and SEA analysis.


2005 ◽  
Vol 12 (4) ◽  
pp. 225-235 ◽  
Author(s):  
Jeremy W. Trevathan ◽  
John R. Pearse

Results are presented for the numerically predicted sound transmission loss of a finite panel excited by plane wave sources at various angles of incidence. It is shown that the limitation commonly imposed upon the integration of the ‘mass law’ is not arbitrary. Rather, it is the upper integration limit at which a function dependent on cos2 (the ‘mass law’), when integrated, becomes equal to a function dependent on cos (the method used in this study, the ISO 140 experimental method) which has been integrated from zero to 90 degrees. The current definition of sound transmission loss implicitly assumes that a plane wave sound source at normal incidence to the panel surface will produce the highest level of excitation in the panel, and as the angle of incidence is increased the panel will experience decreasing levels of excitation. However, it is shown here that the excitation experienced by a panel due to a plane wave source is almost independent of the angle of incidence.


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