GB/T 3767-1996
Acoustics--Determination of sound power levels of noise sources using sound pressure--Engineering method in an essentially free field over a reflecting plane (English Version)

Standard No.

GB/T 3767-1996

Language

Chinese, Available in English version

Release Date

1996

Published By

General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China

Status

Be replaced 2016-09

Replace By

GB/T 3767-2016

Latest

GB/T 3767-2016

Replace

GB 3767-1983

Scope

General This standard specifies a method for calculating the sound power level of a noise source by measuring the sound pressure level on a measurement surface enveloping a sound source under approximately free-field conditions in the vicinity of one or more reflecting surfaces. At the same time, the test environment, the requirements of measuring instruments and the calculation methods of surface sound pressure level and sound power level are given. The accuracy level of the measurement results of the sound power level is level 2. For various types of equipment, it is very important to formulate and use its specific noise test specifications according to this standard. The noise test specification should give a detailed description of the installation, load, working conditions, measurement surface and microphone array selection of the sound source to be tested. Note 1 to entry: For a particular type of equipment, the noise test specification should give details of the specific measurement surface chosen, since the use of different shapes of measurement surfaces will result in different evaluations of the sound power level of the sound source. Types of noise and noise sources The methods specified in this standard are applicable to the measurement of various types of noise. Note 2: See GB/T 14529 for noise classification (recessive state, non-recessive state, quasi-steady state, pulse, etc.). This standard is applicable to all types and sizes of sound sources (equipment, machines, parts, assemblies, etc.). This standard does not apply to super high or long sound sources, such as chimneys, pipelines, conveying machinery, industrial equipment with multiple sound sources, etc. Test environment This standard applies to a test environment that is near a free field near one or more reflective surfaces indoors or outdoors. Measurement uncertainty According to the results measured in this standard, except for a few cases, the standard deviation of the reproducibility of the A-weighted sound power level is equal to or less than 1.5dB (see Table 1). There is likely to be a difference within the uncertainty range between the single value of the sound power level of the noise source measured according to this standard and its true value. The uncertainty of the sound power level measurement comes from the comprehensive influence of the environmental conditions of the measurement laboratory and the experimental technology. If the sound power level of a specific noise source is measured according to this standard in different laboratories, the measurement results will show dispersion. See GB/T 14573.4 for calculation of standard deviation of measurement results and is related to frequency. Except for individual cases, the above standard deviations do not exceed the values in Table 1. The reproducibility standard deviation qr given in Table 1 takes into account the cumulative effect of uncertainty in the measurement process, but does not include changes in sound power output caused by changes in operating conditions (speed, power supply, voltage) or installation conditions. Measurement uncertainty is not only related to the reproducibility standard deviation, but also to the required confidence level. For example, for a normally distributed sound power level, when the confidence level is 90%, the true value of the sound source sound power level is within the range of -1.645qr of the measured value, and when the confidence level is 95%, the true value is located within +- of the measured value 1.960qr range. See GB/T 14573 series and ISO 9296 for details. Table 1 Estimated value of standard deviation of sound power level reproducibility measured according to standard Octave band center frequency 1/3 octave band center reference rate reproducibility standard deviation qr Hz Hz dB 63 50～80 5¹⁾ 125 100～ 160 3 250 200~315 2 500~4 000 400~5 000 1.5 8 000 6 300~10 000 2.5 A-weighted 1.5²⁾ 1) Generally suitable for outdoor measurement, many rooms are not satisfied with this frequency band. 2) Applicable to sound sources whose radiated noise spectrum is relatively "flat" in the range of 100-10 000 Hz Note 3 The standard deviation listed in Table 1 is the comprehensive effect of the measurement conditions and methods defined in this standard, not including the sound source itself They are caused by variations between measurement sites, including outdoor environmental and climatic conditions, indoor room geometry and boundary sound absorption, acoustic properties of reflective surfaces; background noise; calibration form of instruments; and experimental technique Changes in the measurement surface, including the shape and size of the measurement surface, the number of measurement points and the positioning of the microphone, the position of the sound source, the integration time, the determination of the environmental correction (if any). The standard deviation is also affected by the error caused by the near-field measurement, which is related to the characteristics of the sound source. When the measurement distance is small and the involvement is low (below 250Hz), the error will generally increase. If several real

GB/T 3767-1996 history

• 2016 GB/T 3767-2016 Acoustics—Determination of sound power levels and sound energy levels of noise sources using sound pressure—Engineering methods for an essentially free field over a reflecting plane
• 1996 GB/T 3767-1996 Acoustics--Determination of sound power levels of noise sources using sound pressure--Engineering method in an essentially free field over a reflecting plane
• 0000 GB 3767-1983