ANSI HI-9.4-2000 pdf download
The purpose of this standard is to provide uniftorm test procedures for the measurement of airborne sound trom pumping equipment. This standard applies to centriugal, rotary, and recip- rocating pumping equipment and specifies procedures and operating conditions acceptable and expedient for use by non-specialists as well as by acoustic engi- neers. This standard does not apply to vertical submerged wet pit pumps. In this standard, a sound pressure level of 20 upascals (0002uBAR) is used as reference.
9.4.1 Instrumentation The instrumentation required for carrying out the tests herein is as follows:
9.4.1.1 Sound level meter and microphone system The sound level meter and microphone system shall meet the requirements of IEC 179 or shall be calibrated to meet the requirements of IEC 179 or ANSI S1.4, type 1.
9.4.1.2 Octave-band analyzer The octave-band analyzer shall meet the requirements of ANSI S1.11.
9.4.1.3 Acoustical calibration The entire instrumentation system including the microphone and cable shall be calibrated at a convenient frequency before and after each test series using a suitable calbrator. Annually, the frequency response of the system should be checked to verify its accuracy at all frequencies in the range of interest. This calibration should be traceable to the NIS T.
9.4.1.4 Recorders If a tape recorder or graphic level recorder is used, its stability and frequency response shall at least equal those of the sound level meter and microphone system over the frequency range of interest.
9.4.2 Operation of pumping equipment Whenever possible, sound tests shall be made with the pump operating at rated application conditions. If this operating condition cannot be obtained, then sound tests may be made at some other conditior mutually agreed upon by the parties concerned. TH test conditions shaill be clearly described in the test report.
9.4.3 Test environment It is desirable to conduct tests in a free field above a reflecting plane and not influenced by reflections from walls and nearby objects. A six (6) dB drop-off in sound pressure level in each octave band of interest in all directions around the machine, regardless of distance, indicates approximate free-field conditions and gives sufficient accuracy for the purposes of this test standard.
If a 6 dB drop-off cannot be obtained, the room can often be modifhed to meet this objective by covering the walls and other large surtaces near the measuring points with a sound absorptive material. Otherwise, room correction factors must be developed. The substitution method, using a calibrated reference sound source, is recommended for determining these factors. The reference sound source should have white noise” characteristics and its free-field sound pressure levels must be known. (A commonly used sound source is one manufactured by ILG Industries, Chicago, IL.) By the substitution method, the reference sound source is placed in the test area, in lieu of the test pump, with its acoustic center located at the same point in the room as that of the pump. While the reference sound source is operating, octave-band sound pressure levels and the A-weighted sound level are measured at exactly the same microphone locations that are used for measuring the pump’s sound levels. These measured levels, corrected for the background noise, are subtracted from the known free-field levels (for the particular source-to-microphone distance) of the reference sound source. The results are the room correction factors and are added to the pump’s sound levels to develop its free-field values.