1. This standard specifies a reflecting plane of the top eight for the free field testing environments. Envelope in a false measurement of the sound source sound pressure level measured on the surface. To calculate the sound power levels – Engineering method to determine the finished leather machinery (including tanning machinery, wool leather machinery, shoes machinery,leather cutting machine, leather machinery hereinafter) of the sound power level. The data obtained to evaluate or compare the acoustic performance of leather machinery products.
2.This standard applies to steady-state radiation, unsteady broadband or narrowband noise of all types of leather machinery. Does not apply to radiation pulses noise and leather machinery linear dimensions (length, width or height) exceeds 15m leather machinery.
3. This standard is based on the gb / t 3767 “sound power levels of noise sources – Determination of engineering works and quasi-Law” works of law principles. Reference is also made in the preparation of iso 3744 “Acoustics – voice sound source sound power level measurement – For a free field conditions over a reflecting plane Engineering method.” Standard terminology used, the amount and bit and symbols are in accordance gb / t 3947 “Acoustics terminology” and gb 3l02.7 “acoustic quantities and units” and other relevant provisions of national standards.
Second, the need to determine the amount and measurement uncertainty
1 Determination of the amount to be
a band sound power level or sound power level, other interest-weighted sound power level and directivity index determination without satin set. Selected according to the needs.
2. Measurement Uncertainty
To thousands of radiation in the frequency range 100 ~ 10000hz uniform spectral density leather machinery. A sound power level measurement standard deviation is not dry 2db. Measuring octave band and 1/3 octave band sound power standard deviation is less than the requirements in Table 1.
Main: ① standard deviation reflects a variety of factors caused by the cumulative effect of measurement uncertainty, including as a result of individual tests leather machinery installation and operating conditions may cause a change in the sound power level changes.
② In the outdoor measurements, the center frequency of 63hz octave band sound power level of the standard deviation of 5db.
Third, the testing environment
1. suitable for the standard test environment should be one having a reflecting plane (usually concrete or asphalt), a free sound field above a large room (such as assembly shop) or outdoor plaza.
2.measurement of the surface can not have any sound absorbing objects reflecting object (including personnel). The outer surface of the measurement should be possible without reflectors.
3. When the actual test environment deviate from the ideal free-field conditions, you should use a method to determine the environment in Appendix correction value k2, and the measurement results awakened corrected this environment correction value k2 (or a / s value) must satisfy k2 <2.2db (or a / s> 6).
Note: a / s between the definition and determination of the appendix a a2.
4 running low SPL 6db more responsible measure invalid. When the measured sound pressure level of the background noise level is less than or equal to 10db, should be amended.
5 When the test environment temperature, pressure deviation from standard ambient conditions (temperature t = 20 ℃, pressure po = 100kpa) caused by the correction value is equal to or greater than 0.5db, should be amended.
6.in the outdoor test, the customs should be <6m / s (equivalent to 4 winds), and use the wind shield.