ASTM E90 Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements

Scope:

ASTM E90 test method covers the laboratory measurement of airborne sound transmission loss of building partitions such as walls of all kinds, operable partitions, floor-ceiling assemblies, doors, windows, roofs, panels, and other space-dividing elements.

Test Procedure:

In ASTM E90, two adjacent reverberation rooms are arranged with an opening between them in which the test partition is installed (Figure 1). The only significant sound transmission path between rooms is by way of the test partition. An approximately diffuse sound field is produced in one room – the source room. Sound incident on the test partition causes it to vibrate and create a sound field in the second room – the receiving room. The space- and time-averaged sound pressure levels in the two rooms are determined. In addition, with the test specimen in place, the sound absorption in the receiving room is determined. The sound pressure levels in the two rooms, the sound absorption in the receiving room, and the area of the specimen are used to calculate sound transmission loss. Because transmission loss is a function of frequency, measurements are made in a series of frequency bands.  

In theory, it is not important which room is designated as the source and which is the receiving room. In practice, different values of sound transmission loss may be measured when the roles are reversed. To compensate for this, the entire measurement may be repeated with the roles reversed; the source room becomes the receiving room and vice versa. The two sets of transmission loss values are then averaged to produce the final result for the ASTM E90 test.

Figure 1: Illustration Showing Conceptual Arrangement of a Wall Sound Transmission Loss Suite

Figure 2: Illustration Showing Filler Wall and Test Specimen that is Smaller Than the Test Opening

Specimen size:

The test specimen used in ASTM E90 testing may either be built into a suitable frame, which is then inserted in the test opening, or built into the opening itself. Specimens shall be built in accordance with usual construction practice except that extra control procedures may be necessary to ensure maintenance of the specified dimensions.

Data

In ASTM E90, the sound transmission loss at each frequency f is calculated using the formula:

TL (f) = L_S(f) – L_R (f) +10 log S/A_R(f) 

Where:

TL (f) = transmission loss, dB,

L_S (f) = average sound pressure level in the source room, dB,

L_R (f) = average sound pressure level in the receiving groom, dB,

S = area of the test specimen that is exposed to the receiving room, m2, and

A_R (f) = sound absorption of the receiving room with the test specimen in place, m2 

When measurements are made in both directions, the final value of transmission loss to be reported shall be calculated using:

TL (f) = (TL₁ (f) – TL₂ (f))/2 

Where TL₁ (f) and TL₂ (f) correspond to the two directions of measurement.

If TL₁ (f) or TL₂ (f) is invalid (for example, because of excessive background noise) then the remaining valid measurements shall be used for TL (f).

Conclusion:

ASTM E90 test method covers the laboratory measurement of airborne sound transmission loss of building partitions such as walls of all kinds, operable partitions, floor-ceiling assemblies, doors, windows, roofs, panels, and other space-dividing elements.