GB/T 21228.2-2023 English PDF

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GB/T 21228.2-2023: Acoustics - Sound-scattering properties of surfaces - Part 2: Measurement of the directional diffusion coefficient in a free field
Status: Valid

Standard ID	USD	BUY PDF	Lead-Days	Standard Title (Description)	Status
GB/T 21228.2-2023	384	Add to Cart	4 days	Acoustics - Sound-scattering properties of surfaces - Part 2: Measurement of the directional diffusion coefficient in a free field	Valid

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Basic data

Standard ID: GB/T 21228.2-2023 (GB/T21228.2-2023)
Description (Translated English): Acoustics - Sound-scattering properties of surfaces - Part 2: Measurement of the directional diffusion coefficient in a free field
Sector / Industry: National Standard (Recommended)
Classification of Chinese Standard: A42;P31
Classification of International Standard: 91.120.20
Word Count Estimation: 20,296
Date of Issue: 2023-05-23
Date of Implementation: 2023-12-01
Issuing agency(ies): State Administration for Market Regulation, China National Standardization Administration

GB/T 21228.2-2023: Acoustics - Sound-scattering properties of surfaces - Part 2: Measurement of the directional diffusion coefficient in a free field

---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
ICS 91:120:20 CCSA42;P31 National Standards of People's Republic of China Acoustic Surface Sound Scattering Properties Part 2: Free-field directional diffusion coefficient measurement (ISO 17497-2:2012, IDT) Released on 2023-05-23 2023-12-01 implementation State Administration for Market Regulation Released by the National Standardization Management Committee

table of contents

Preface I Introduction II 1 Scope 1 2 Normative references 1 3 Terms and Definitions 1 4 Measuring principle 3 5 frequency range 3 6 Measurement arrangement 4 6:1 Measurement environment 4 6:2 Measurement area 5 6:3 Specimen 7 7 Test method 7 7:1 Test signal 7 7:2 Sound source and receiving equipment 7 7:3 Measurement 7 7:4 Processing of Polar Coordinate Responses 8 8 Result expression 11 8:1 Directional diffusion coefficient 11 8:2 Normalized directional diffusion coefficient 11 8:3 Calculation of area factor 12 8:4 Random incidence diffusion coefficient 12 8:5 Results expression 13 9 Test report 13 Appendix A (Normative) Requirements for Measurement Space 14 A:1 Space requirements14 A:2 Environmental conditions 14 A:3 Placement requirements 14 Reference 15

foreword

This document is in accordance with the provisions of GB/T 1:1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules for Standardization Documents" drafting: This document is part 2 of GB/T 21228 "Sound Scattering Characteristics of Acoustic Surfaces": GB/T 21228 has issued the following parts: --- Part 1: Measurement of scattering coefficient of random incident sound in reverberation chamber; --- Part 2: Free field directional diffusion coefficient measurement: This document is equivalent to ISO 17497-2:2012 "Acoustic Surface Sound Scattering Properties Part 2: Free Field Directional Diffusion Coefficient Measurement": The following minimal editorial changes have been made to this document: ---Changed the index number description 5 in Figure 1, and changed the "receiver" in ISO 17497-2:2012 to "receiving point trajectory (arc or sphere)", to make the explanation clearer: Please note that some contents of this document may refer to patents: The issuing agency of this document assumes no responsibility for identifying patents: This document was proposed by the Chinese Academy of Sciences: This document is under the jurisdiction of the National Acoustic Standardization Technical Committee (SAC/TC17): This document was drafted by: Institute of Acoustics, Chinese Academy of Sciences, Tongji University, Hangzhou Aihua Intelligent Technology Co:, Ltd:, Chongqing University, Zhengzhou Hongsen Energy Saving Technology Co:, Ltd:, Southeast University, China Academy of Building Research Co:, Ltd:, Nanjing University, Qingdao University of Technology: The main drafters of this document: Lu Yadong, Li Xiaodong, Cheng Xiaobin, Mo Fangshuo, Xiong Wenbo, Jiang Guorong, Yu Wuzhou, Xie Hui, Zhang Jianxun, Fu Xiuzhang, Tan Hua, Tao Jiancheng, Xu Xin, Yin Cho, Liu Bilong:

Introduction

The degree of surface sound scattering is very important in various occasions of room acoustics (such as: concert halls, recording studios, workshops and reverberation rooms, etc:): indoor The degree of scattering and absorption is an important factor affecting the sound quality of the room: This document deals with the measurement and characterization of scattering surfaces: GB/T 21228 is proposed to be divided into the following parts: --- Part 1: Reverberation chamber random incident sound scattering coefficient measurement: The purpose is to describe the force from the surface caused by the surface roughness The degree to which the acoustic reflection deviates from the specular reflection: --- Part 2: Free field directional diffusion coefficient measurement: The aim is to describe the space of surface acoustic scattering that characterizes the quality of diffuse surfaces: distribution characteristics: The random incident sound scattering coefficient introduced in Part 1 of GB/T 21228 is different from the directional diffusion coefficient described in this document The former describes the degree of sound scattering, and the latter describes the directional uniformity of sound scattering: The two are related, and they have different applications: use the occasion: Acoustic Surface Sound Scattering Properties Part 2: Free-field directional diffusion coefficient measurement

1 Scope

This document describes a method for measuring the directional diffusion coefficient of a surface: The diffusion coefficient describes the uniformity of the directional distribution of the surface reflected sound, and is an index to measure the scattering characteristics of the surface sound: The user accounts for the sound diffusing properties of surfaces and also provides information for developers and users of predictive room acoustics models: However, the diffusion coefficient is not Suitable directly as an input to the current diffusion algorithm in the geometric-acoustic model of the room: This document also details methods for characterizing the sound diffusion properties of surfaces in a free field:

2 Normative references

The contents of the following documents constitute the essential provisions of this document through normative references in the text: Among them, dated references For documents, only the version corresponding to the date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to this document: Note: Commonly used frequencies in GB/T 3240-1982 acoustic measurement (neqISO 266:1975) IEC 61260 Electroacoustic octave and fractional octave filters (Electroacoustics-Octave-bandandfractional- Note: GB/T 3241-2010 Electroacoustic octave and fractional octave filters (IEC 61260:1995, MOD)

3 Terms and Definitions

The following terms and definitions apply to this document: 3:1 sound ray soundray A line originating from the point of sound source that traces a possible direction of sound propagation: 3:2 Specular reflection specular reflection Reflection that obeys Snel's law (that is, the angle of reflection equals the angle of incidence): NOTE: Specular reflection can be approximated by a rigid plane much larger than the wavelength of the incident sound: 3:3 Specular reflection area specularzone The area enclosed by the sound rays from the virtual sound source (i:e: the specific reference plane and the sound rays around the edge of the reference plane and the receiving point arc or the area formed by the sphere): Note 1: The reference plane is a rigid plane with the same projected shape or footprint as the surface of the test piece: Note 2: The position where the sound rays from the virtual sound source to the receiving point pass through the diffuser is the specular reflection point (see Figure 1): ......

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