Thin plate in a test facility

A transmission loss test facility consists of two rooms connected by an opening. The specimen to be measured is placed in the opening. One room has one or more sound sources and is called "source room". The other room is called "receiving room".

According to the norm DIN EN ISO 10140-2, the transmission loss (R) is calculated with the expression


L1 : mean pressure in source room

L2 : mean pressure in receiving room

S  : area of opening

A  : equivalent absorbing area in receiving room

The definition above requires that the sound field in both rooms are diffuse and that the sound in the receiving room is exclusively due to the sound coming through the test element.

To obtain accurate values, the source and microphone positions should be at certain distance away from the boundaries of the rooms and the partition as well.

Sound field in the rooms

To maintain the number of elements small, a boundary element method is selected for the numerical simulations.

The whole surface of the acoustic domain is subdivided in 4 surfaces S1-S4. S2corresponds to the surface of the thin plate and S3 to the rigid surface between the rooms. S1 and S4 are considered absorbing surfaces.

pI  : pressure in source room, pI=[pI1  pI2  pI3]T

pII : pressure in receiving room, pII=[pII2  pII3  pII4]T

w   : displacement of the plate

The sound transmission from source room to receiving room through the partition is the result of an acoustic-structure interaction.

Lp : operator for motion of the plate in vacuum

A   : matrix relating elements of S2 with S1-S4

HI, GI, HII, GII: operators relating p on S1-S4 with w

ps : pressure due to the source

The unknown quantities on the surface w, pI and pII are obtained by solving the coupled system of equations given by

Knowing the sound pressure on the surfaces S1-S4 and the plate displacement of the plate, the mean pressure in source and receiving rooms can be computed and the transmission loss determined.




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R. Piscoya, M. Ochmann, Transmission loss of corrugated plates, Proc. Forum Acusticum, Aalborg, 2011. [pdf]


R. Piscoya, M. Ochmann, Berechnung der Schalldämmung von dünnen Platten in einem Kanal, Proc. DAGA 2012, Darmstadt, 2012. [pdf]


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R. Piscoya, M. Ochmann, Calculation of the transmission loss of thin plates in a Kundt's tube, Proc. Euronoise 2012, Prague, 2012. [pdf]


R. Piscoya, M. Ochmann, Iterative approach for transmission loss simulations, Proc. DAGA 2013, Merano, 2013. [pdf]