Accession Number : ADA183348

Title :   Sound Power Measurements in Air in the Near Field of Sound Sources Using the Sound Intensity Method.

Descriptive Note : Final rept. 1 Mar-1 Oct 85,

Corporate Author : CHICAGO UNIV ILL MATERIALS RESEARCH LAB

Personal Author(s) : Polak,John R

PDF Url : ADA183348

Report Date : Oct 1986

Pagination or Media Count : 67

Abstract : Sound power is the acoustic energy output in watts of a sound-producing source. Sound power can be determined with an array of pressure sensing transducers placed around a source in an anechoic chamber, as specified in standard 3744-1981 (E). In contrast, sound intensity can be used to measure sound power by measuring the intensity output of the source in watts/sq. m. over a closed surface and using the definition of sound power (intensity X area) to find sound power. Advantages of the sound intensity method are that one measuring probe is used, which consists of two closely placed pressure sensing transducers: no anechoic chamber is needed; measurements can be done in the near field; and background noise can be present. Disadvantages are that: no standards exist yet; and the phase response between the two transducers in the probe must match closely, either through quality transducers or by careful calibration. The two methods of determining sound power were systematically compared. Tests showed that the sound power results from the sound intensity method, even in fairly adverse environments, were comparable to results obtained using the ISO method in most situations.

Descriptors :   *PRESSURE TRANSDUCERS, *ACOUSTIC MEASUREMENT, *POWER LEVELS, *SOUND PRESSURE, ACOUSTIC EMISSIONS, STANDARDS, ACOUSTIC DETECTION, EXPERIMENTAL DESIGN, TEST EQUIPMENT, ACOUSTIC WAVES, ADVERSE CONDITIONS, ANECHOIC CHAMBERS, BACKGROUND NOISE, CALIBRATION, INTENSITY, MEASUREMENT, NEAR FIELD, OUTPUT, POWER, PROBES, QUALITY, RESPONSE, SOUND, SOUND GENERATORS, TRANSDUCERS

Subject Categories : Acoustic Detection and Detectors
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE