Several ASTM test methods to evaluate the sound-insulating properties of building elements require the measurement of room sound absorption as part of the procedure. The room sound absorption in these standards appears in an equation in the form 10 log (x/A), where x is a quantity with the same units as A, m². Room sound absorption is calculated from the decay rate using Eq 1.

The requirements of this standard have been chosen so the uncertainty associated with the measurement of room sound absorption will be acceptably small so long as the logarithm of the absorption is being used in calculations.

Other test methods should specify explicitly that they make use of this test method.

Where measurement requirements in the parent standard differ from those given here, the requirements in the parent standard shall be satisfied.

This test method shall not be used when room sound absorption or decay rate is to be used directly to satisfy some criterion, for example in a room that must not be overly reverberant so speech will be intelligible.

Note 1—The uncertainty of the room sound absorption obtained will usually be too high and additional measurements are necessary.

Any companion standard may specify the use of the procedures in this method for determining whether the decay rates in a room are slow enough to satisfy the requirements of the companion standard. The measured decay rates shall still be used only to calculate the logarithm of the room absorption.

1.1 This test method covers the measurement of sound decay rate in rooms and the calculation of the sound absorption of the room and its contents. The sound absorption so calculated may be used in calculations in sound insulation test methods.

1.2 The method shall be used only in conjunction with other test methods where the logarithm of the sound absorption is used in formulas. It is not sufficiently precise for use in situations where room sound absorption is to be used without taking logarithms.

1.3 For laboratory measurements of the sound absorption of materials and objects, Test Method C 423 should be used.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.