GB/T 6881.1-2002Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Precision methods for reverberation test rooms (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

This document replaces GB/T 6881.1-2002 "Acoustic Sound Pressure Method for Determining the Sound Power Level of Noise Sources Reverberation Chamber Precision Method" and is consistent with Compared with GB/T 6881.1-2002, in addition to structural adjustments and editorial changes, the main technical changes are as follows.

---Added 3.4, 3.14, 3.17, and 3.18 in terms and definitions (see Chapter 3), and deleted "mean square sound pressure" (see the 2002 edition of 3.4);

---Added sound energy level measurement part (see Chapter 9 and Appendix F);

---Added more detailed content on measurement uncertainty (see Chapter 10).

This document is equivalent to ISO 3741:2010 "Acoustic Sound Pressure Method for Determination of Sound Power Level and Sound Energy Level of Noise Sources Reverberation Chamber Accuracy" Secret Dharma".

Please note that some content in this document may be subject to patents. The publisher of this document assumes no responsibility for identifying patents.

Introduction

This document is one of the standards corresponding to the ISO 3740[3]~ISO 3747[9] series of international standards. This series of standards specifies the determination of Various methods of sound power levels and sound energy levels of machines, equipment and their components. Which method to choose from among a series of standards corresponding to different applications the method depends on the purpose of measuring the sound power level and the facilities available. ISO 3740 [3] provides general guidance for the selection of methods.

The ISO 3740[3]~ISO 3747[9] series of standards only give general principles for the operating and installation conditions of machine equipment during measurement. It is necessary for each Establish test specifications for each type of sound source to give detailed requirements for installation, load and operating conditions, and obtain the sound power level under these conditions.

or sound energy level.

The method given in this document requires that the sound source under test be installed in a reverberant chamber with specific acoustic characteristics. Therefore, the premise of this method is that the measured the sound power or sound energy of a sound source is directly proportional to the mean square sound pressure averaged in time and space, and only depends on the acoustic and geometric characteristics of the room and the space.

Physical constants of gas.

For sound sources emitting narrowband frequency or discrete frequency sound, precise measurement of the radiated sound power level or sound energy level in the reverberation room requires Does more work than a sound source that emits sound evenly over a wide frequency range. The reasons are.

a) The spatio-temporal average sound pressure measured by moving a microphone along a short distance or measured by an array composed of a small number of microphones is not always the average sound pressure of the entire room.

A good estimate of the temporal and spatial average sound pressure;

b) The normal form of the room and the position of the sound source within the room have a strong influence on the sound power or sound energy radiated by the sound source.

For sound sources that emit narrowband sound or discrete modulated sounds, the increased measurement workload includes optimization and performance qualification of the reverberation chamber or the use of more the position of the sound source and the position of the microphone (or increase the length of the moving distance of the microphone). Add low-frequency sound absorbers or install rotating diffusers in the reverberation room body helps reduce measurement workload.

The method specified in this document allows the determination of sound power levels and sound energy levels in the 1/3 octave band and from them the calculation of octave band, A-weighted and unweighted total sound power level and sound energy level.

The method described in this document meets the level 1 accuracy (precision level) defined in GB/T 19052, and the final sound power level and sound energy level package Corrections are included for possible differences between the meteorological conditions during the test period and the baseline meteorological conditions. For acceptable reverberation loops at lower accuracy for applications in the environment, please refer to ISO 3743-1[4], ISO 3743-2[5], and ISO 3747[9].

Acoustic sound pressure method determines the sound power level and sum of noise sources Sound energy level reverberation chamber precision method

1 Scope

2 Normative reference documents

The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, the dated quotations for undated referenced documents, only the version corresponding to that date applies to this document; for undated referenced documents, the latest version (including all amendments) applies to this document.

GB/T 3241-2010 Electroacoustic octave and fractional octave filters (IEC 61260:1995, MOD)

Note 1.There is no technical difference between the quoted content of GB/T 3241-2010 and the quoted content of IEC 61210:1995.

GB/T 3785.1-2010 Electroacoustic sound level meter Part 1: Specification (IEC 61672-1:2002, IDT) GB/T 15173-2010 Electroacoustic sound calibrator (IEC 60942:2003, IDT) GB/T 19052-2003 Guidelines for the drafting and presentation of noise test specifications for noise emitted by acoustic machines and equipment (ISO 12001:1996,IDT) ISO 3382-2 Measurement of acoustic parameters of acoustic rooms Part 2: Reverberation time of ordinary rooms (Acoustics-Measure-