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absorption coefficient

absorption coefficient

absorption coefficient

(OP)
while studying vibrations I constantly came across 2terms: transmissionloss factor and absorption coefficient.
Where excatly is the difference? Can one generaly say, that the transmissionlossfactor is for menachnical vibrations, whereas the other one is for acoustical purpose?
Thanks,
Aoife

RE: absorption coefficient

Sort of. You can have an acoustic TL, in an exhaust for example, or when measuring the sound transmitted through (as opposed to reflected off) a panel.

Cheers

Greg Locock

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RE: absorption coefficient

for a sound wave, when it encoutered a plate or some object, the energy (E) will be seperated into three parts. some of them (Er) will be reflect, the other part will enter into the structure. then some energy (Ea) will be absorbed by the struction because of damp and visuoelastic. finnally, the energy left (El) will be through the structure. So,
E=Er+Ea+El
for transmission loss, is E-El.
for aborption coefficient, is Ea/E.

RE: absorption coefficient

Note also that TL requires an anechoic termination.  It is the ratio of incident sound power to that transmitted downstream to an anechoic termination.

- Steve

RE: absorption coefficient

One (TL) is a measure of barrier material performance; the other (absorption coefficient) is a measure of absorber performance.  TL in acoustic usage describes an acoustic property,  not a mechanical one.
Just as the two types of  materials are fundamentally different,  so are these tests.

RE: absorption coefficient

"transmission loss factor and absorption coefficient"

When I lived in a 1960s side-by-side duplex apartment our neighbor had a teenaged daughter, and my outspoken wife is from the Bronx, New York . I bet we all were glad the "common" wall had a relatively high transmission loss, and it was sealed at the edges, so there were no flanking paths for sound to sabotage its performance.

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