ASME PTC 36:2018 pdf free download – Measurement of Industrial Noise
While the test machine or facility is not operating, the background-sound level or sound-pressure level shall be measured at all the test microphone locations for all octave bands or one-third octave bands of interest. The back- ground-sound measurements shall include the operation of any ancillary equipment necessary for the operation of the equipment being tested. See para. 4-2.8. While the test machine is running, the sound-pressure level at each location should ideally exceed the background- soundlevelorsound-pressurelevelbyatleast10 dB foreachoctaveband. Sound-leveldifferencesless than10 dB maybe adjusted or corrected as provided in Mandatory Appendix I.
4-2.7 Microphone Positions
For measurements of near-field sound-pressure level, it is usually sufficient to select locations 3.3 ft (1 m) from the major vertical surfaces ofthe machine ata heightof5 ft± 1 ft(1.5 m ± 0.3 m) above the floor or walklevel. Measurement locations shall be established relative to an imaginary parallelepiped, which will justenclose the source, omitting minor projections.
4-2.8 Measurement Technique
The measurement techniques prescribed in the respective standards shall govern. If unique test conditions require departures fromprescribedtechniques, anexplanationofthe reasons forthe departures shall be giveninthe final report. Inanymeasurement, the observer’s bodyshallremainatleast1.6 ft(0.5 m) fromthe microphone. Theobservershallin no eventbe between the microphone and the sound source. The microphone should be oriented as recommended bythe manufacturer. NOTE: If strong discrete-frequency components are present, large fluctuations in sound-pressure levels may occur because of the interference between directsound waves and those from reflective surfaces such as the floor, the ground, ornearbywalls orbuildings. Atmospheric in-homogeneities exhibit similar influences on far-field measurements.
4-3.1.1 The data forms ofthe standards referenced in this Code may be used to prepare test reports for the measure- ments obtained using the procedures ofthis Code. The data obtained using the procedures ofthis Code may be used to define the near-field sound-pressure levels or to determine far-field sound-pressure levels at prescribed positions.
4-3.1.2 Refer to Nonmandatory
Appendix B of this Code for guidelines regarding the application of the referenced procedures to expected industrial sound measurement situations.
4-3.1.3 Distinguishing elements of the ANSI/ASA S12.18 procedure are as follows:
(a) ANSI/ASAS12.18 defines two methods formeasuringsound-pressure levels; however, these provisions are speci- fically intended for measurements outdoors. Therefore, caution is required ifthese procedures are applied to near-field measurements indoors.
(1) Method 1. The general method outlines conditions for routine measurements and is used if meteorological variables fall within broad but predetermined limits. No effort is made to control the acoustical environment, i.e., the environment is accepted “as is”. A hand-held sound-level meter, which provides a frequency-weighted and time-averaged sound level, is usually used for this method, but instruments for frequency band analysis may also be used.
(2) Method2. This method describes strictmeteorological, ground, and other conditions that, ifmaintained, enable accurate, reproducible measurements ofsound-pressure levels. The acoustical environmentmaybe left“as is,” or itmay be modified or controlled, per the method guidelines, for better accuracy. Procedures are suggested to adjust the measured sound-pressure levels to reference conditions. This precision method is suited for frequency band analysis, but also provides more accurate frequency-weighted sound-pressure levels, if required.
(b) Standardized receiver locations are not prescribed in ANSI/ASA S12.18.