scope:

This American National Standard describes a method for the determination of sound power levels of noise sources that emit broadband sound and/or discrete frequency sounds/tones in reverberation rooms. The method described herein requires reverberation room pre-qualification through test and requires the use of the comparison method to determine sound power levels. This standard specifies the physical environment, procedures, and equipment used to qualify the reverberation room by test. Pre-qualifying the room ensures adequate modal density for the use of one source location to obtain acceptable accuracy and repeatability of results. The reference sound source (RSS) used for the comparison method relies on AHRI Standard 250 to accurately describe the performance and characterize the sound power of the RSS at all frequencies of interest. Sound rating values are often useful for applications and design; therefore, it is important to acquire data and qualify measurement rooms in one-third octave bands. The use of the comparison method reduces a number of potential sources of error. This standard contains information on instrumentation, installation, and operation of the source; procedures for determining the number of microphone positions or length of traverse; and procedures for the calculation of sound power level. Measurements made in conformity with this standard will, with very few exceptions, result in standard deviations equal to or less than specified in Table 1.

The frequencies covered in this standard range from the 50 Hz to the 10,000 Hz one-third octave bands (63 Hz to 8000 Hz octave bands). The 50 to 80 Hz one-third octave band sound frequently affects product applications and often cannot be ignored. The product-specific standards referring to this method should specify the frequency range of interest for qualification, calculation, and reporting. This standard is based on ANSI/ASA S12.51/ISO 3741 but provides additions, exceptions, and extensions.

This standard is intended to serve as a basic reference to be used in product-specific standards and for the guidance of the industry, including manufacturers, engineers, installers, contractors, and users.

The standard is appropriate for all noise sources but is especially appropriate when it is either undesirable or unfeasible to move the source to decrease the uncertainty of the measurement.

This standard applies to products where sound power is determined by measurement using the comparison method in a reverberation room that meets the qualification requirements of this standard.