GB/T 10894-2023Determination method of separation machinery noise (English PDF)

5.2 Calibration

5.2.1 Before and after each measurement, the entire test instrument system shall be calibrated at one or more frequencies using a sound calibrator that meets the Level 1 accuracy requirements of GB/T 15173-2010.If the difference between the calibration values before and after the measurement exceeds

0.5 dB, the measurement is invalid.

5.2.2 Sound calibrators shall be calibrated regularly in accordance with JJG 176, and sound level meters and other test instruments shall be calibrated regularly in accordance with JJG 188 to ensure the accuracy of the test instruments.

6.1 Installation

6.1.1 The installation of separation machinery shall comply with the relevant product standards and technical requirements. All accessories shall be installed completely, but no additional sound insulation and sound absorption components shall be added.

6.1.2 Generally, the separation machinery shall be placed directly on the ground or on a test platform for noise measurement. It can also be measured according to the actual installation position, which shall be stated in the test report.

6.2 Operation

6.2.1 The separation machinery shall be started and operated under the operating conditions specified in the relevant product standards or technical documents, and the noise measurement shall be carried out after the operation is stable.

6.2.2 Under no-load operation, for fully enclosed separation machinery, the inlet and outlet can be closed to prevent the noise generated by the airflow at the inlet and outlet from affecting the test; when measuring open-type separation machinery (such as filter centrifuge), if necessary, it is allowed to attach hard paper or filter media to the inner wall of the drum to prevent the additional noise caused by the rotation of the holes.

7.1 Determination of reference box

7.1.1 In order to facilitate the selection of the shape and size of the measurement surface and determine the position of the microphone, a minimum parallelepiped that just surrounds the separation machinery to be measured shall be taken as the reference box. When determining the reference box, small protruding parts on the separation machinery that do not radiate obvious sound (such as handles, connecting pipes, etc.) can be ignored.

7.1.2 If necessary, in order to measure the emission sound pressure level next to the noise source in accordance with GB/T 17248.2, a test bench as small as possible should be used.

7.1.3 This document only specifies the determination of the reference box on one reflecting plane. This document is not applicable to the measurement environment with two or three reflecting planes.

7.2 Selection of measurement surface

7.2.1 General The schematic diagrams of the hemispherical measurement surface and the parallelepiped measurement surface shall comply with the provisions of Appendix B. When measuring, the appropriate measurement surface shall be selected according to the overall dimensions of the separation machinery in accordance with Appendix B. Hemispherical measurement surface is preferred.

7.2.2 Hemispherical measurement surface

7.2.2.1 The center of the hemispherical measurement surface is the projection of the geometric center of the reference box on the reflecting plane (which shall comply with the provisions of Appendix B). The measurement radius r shall be equal to or greater than 2d0 (d0 is the characteristic source dimension), and 1m <= r <= 16m. Calculate the characteristic source dimension according to Formula (1). Where. d0 - characteristic source dimension, in meters (m); l1, l2, l3 - length, width and height of the reference box, in meters (m). l3 - height of the reference box, in meters (m).

7.3 Microphone position

7.3.1 All microphones shall be located on the measurement surface determined in

7.2 and the microphones shall point to the geometric center of the reference box during measurement.

7.3.2 The microphone position and coordinates - divided into basic position and additional position - on the hemispherical measurement surface shall comply with the provisions of B.1.Under the following situations, there shall be additional positions.

a) The variation range (i.e., the difference between the highest sound level and the lowest sound level) of the A-weighted sound pressure level measured at the basic position exceeds 10 dB;

b) The A-weighted apparent directivity index of the separation machinery noise measured exceeds 5 dB in any direction. The determination of the apparent directivity index shall comply with the provisions of

3.24 of GB/T 3767-2016. The coordinates of the additional microphone positions can be measured, by rotating 180° from the coordinates of the basic positions, at the original basic microphone positions (these measurement positions are microphone positions 11 ~ 20). Alternatively, lift the separation machinery to be tested; keep the projection geometric center position of the reference box on the reflecting plane unchanged; rotate it 180°; keep the original microphone positions unchanged, which are the microphone positions 11 ~ 20. For larger separation machinery, the noise source only comes from small areas of the machinery, such as the opening of the closed machinery. The measurement of additional microphone positions shall be carried out in accordance with the provisions of

8.1.1 of GB/T 3767-2016.

7.3.3 The microphone positions on the parallelepiped measuring surface are divided into basic positions and additional positions. There are 9 basic positions and 8 additional positions. The microphone positions and coordinates shall comply with the provisions of B.2.Under the following situations, there shall be additional positions.

a) The variation range (i.e., the difference between the highest sound level and the lowest sound level) of the A-weighted sound pressure level measured at the basic position exceeds the number of measure points;

b) The A-weighted apparent directivity index of the separation machinery noise measured exceeds 5 dB in any direction. The determination of the apparent directivity index shall comply with the provisions of

3.24 of GB/T 3767-2016;

c) The dimension of any side of the reference box is greater than 2 m.