GB 3767-1983Acoustics -- 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 (English PDF)

Foreword

This standard is one of the series of standards for determining the sound power level of noise sources by sound pressure method.

This standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This standard replaces GB/T 3767-1996 "Acoustic sound pressure method to determine the approximate free field above the sound level of the noise source Chengfa.

This standard is compared with GB/T 3767-1996. The main changes are as follows.

--- Added terms and definitions;

--- Increased measurement of sound energy level;

--- The content of measurement uncertainty has been greatly supplemented;

--- Raise the "background noise standard" to "background noise criterion" and formulate relative value criteria and absolute value criteria respectively;

--- Revised the expression of the definition of the directivity index;

--- Increased cylindrical measuring surface; the position of the microphone of the hemispherical discrete pure sound source increased from 10 to 20.

This standard uses the translation method equivalent to ISO 3744:2010 "acoustic sound pressure method to determine the noise source sound power level and sound energy level the Engineering Method for Approximating Free Field Above the Surface (English Version).

The documents of our country that have a consistent correspondence with the international documents referenced in this standard are as follows.

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

---GB/T 4129-2003 Acoustics Performance and calibration requirements for standard sound sources for sound power level determination (ISO 6926.

1999, IDT)

---GB/T 6379 (all parts) Accuracy (accuracy and precision) of measurement methods and results [ISO 5725 (all parts)]

---GB/T 6882-2016 Acoustic sound pressure method for the determination of noise source sound power level and sound energy level anechoic chamber and semi-anechoic chamber precision Law (ISO 3745:2012, IDT) this standard was proposed by the Chinese Academy of Sciences.

This standard is under the jurisdiction of the National Acoustic Standardization Technical Committee (SAC/TC17).

This standard was drafted. Institute of Acoustics, Chinese Academy of Sciences, Shenzhen Zhongya Electromechanical Industry Co., Ltd., Hefei University of Technology, Tongji University, Anhui Vocational and Technical College, Zhejiang University, Shanghai Academy of Environmental Sciences, China Institute of Metrology.

Introduction

This standard corresponds to ISO 3741, ISO 3743 to ISO 3747 GB/T 6881.1, GB/T 6881.2, GB/T 6881.3, One of the GB/T 3767, GB/T 3768, GB/T 6882 and GB/T 16538 series standards.

This series of standards specifies various methods for determining the sound power level and sound energy level of noise sources such as machines, equipment and their accessories.

GB/T 14367 provides a general guide to the choice of method. The choice of measurement method depends on the available test facility environment and sound power the precision required for the level and acoustic energy levels. It may be necessary to establish a noise test specification for individual noise sources (see GB/T 19052) to Appropriately select the acoustic measuring surface and microphone array allowed by GB/T 6881.1 to GB/T 16538 series standard, and give the test unit the required installation, loading and operating conditions are obtained to obtain the sound power level and sound energy level under this condition. A given sound source is emitted to the test loop the sound power of the environment is calculated from the mean square sound pressure and its surface area measured on the imaginary measuring surface surrounding the sound source. The acoustic energy of a single acoustic event is made up of it the sound power and its duration are calculated.

The method specified in this standard allows the determination of the sound power level and the acoustic energy level of the frequency band or A weight.

When the measurement requires higher accuracy, you can refer to GB/T 6882, or GB/T 6881.1 [2], GB/T 16404 [13-15] Line measurement. If the measurement environment related criteria specified in this standard are not met, you can refer to the other standards in this series, or refer to GB/T 16404 [13-15].

This standard describes the measurement of the level 2 accuracy specified in GB/T 19052 in the space near the free surface of the reflecting surface.

method. Such a measurement environment can be a specially designed test room, an industrial building or an outdoor. Ideally, the test source should be installed.

On the acoustic reflection plane of a large open space. For sound sources that are usually installed on the ground inside the building, you need to consider nearby objects, walls and ceilings.

The unwanted reflection of the board and the correction of residual background noise that occurs there.

Acoustic sound pressure method for determining noise source sound power level and Approximate free field above the acoustic energy level reflecting surface Engineering method

1 Scope

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article.

Pieces. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 3785.1-2010 Electroacoustic sound level meters - Part 1. Specification (IEC 61672-1:2002, IDT) GB/T 15173-2010 Electroacoustic Acoustic Calibrator (IEC 60942:2003, IDT) GB/T 19052-2003 Guidelines for the drafting and presentation of noise and noise test specifications for acoustic machines and equipment (ISO 12001:1996, IDT) ISO 3382-2 Acoustic parameters for acoustic test rooms - Part 2. Res.

Measurementofroomacousticparameters-Part 2: Reverberationtimeinordinaryrooms) ISO 3745 acoustic sound pressure method for the determination of noise source sound power level and sound energy level anechoic chamber and semi-anechoic chamber precision method (Acoustics-Determinationofsoundpowerlevelsandsoundenergylevelsofnoisesourcesusing soundpressure-Precisionmethodsforanechoictestroomsandhemi-anechoictestrooms) ISO 5725 (all parts) Accuracy (correctness and precision) of measurement methods and results [Accuracy(truenessandpre-Cision)ofmeasurementmethodsandresults] ISO 6926 Acoustics Performance and calibration requirements for standard sound sources for sound power level determination (Acoustics-Requirements Fortheperformanceandcalibrationofreferencesoundsourcesforthedeterminationofsoundpower Levels) ISO/IEC 98-3 Measurement Uncertainty Part 3. Guidance for the Expression of Uncertainty in Measurement (GUM.1995) [Uncertaintyofmeasurement-Part 3. Guidetotheexpressionofuncertaintyinmeasurement(GUM

1995)]

IEC 61260:1995 Electroacoustic octave and fractional octave filters (Electroacoustics-Octave-bandandfrac-Tional-octave-bandfilters)

3 Terms and definitions

The following terms and definitions apply to this document.

Sound pressure the difference between the instantaneous pressure and the static pressure.

Note 1. Quoted from ISO 80000-8:2007 [21], 8-9.2.

Note 2. The unit of sound pressure is Pascal (Pa).

Sound pressure level Lp the ratio of the square of the sound pressure p to the square of the reference sound pressure p0 is taken as 10 times the logarithm of the base 10, expressed in decibels (dB).

Lp=10lg

P20

In the formula.

P0---reference value, p0=20 µPa.

[ISO/T R25417.2007 [20], 2.2]

Note 1. If frequency and time weighting or a specific frequency band is specified in GB/T 3785.1, it is indicated by an appropriate subscript, for example, LpA indicates A weighting sound.

Pressure level.

Note 2. This definition refers technically to ISO 80000-8:2007 [21], 8-22.

Time average sound pressure level time-averagedsoundpressurelevel Lp,T the ratio of the time average of the sound pressure p squared to the square of the reference value over the specified duration T (starting at t1, ending at t2), 10 times the logarithm of the bottom 10, expressed in decibels (dB).

Lp, T = 10lg

Tintegral

P2(t)dt

P20

In the formula.

P0---reference value, p0=20 µPa.

Note 1. Since the time-averaged sound pressure level should be measured within a certain measurement period, the subscript "T" is generally omitted.

Note 2. When the time average sound pressure level is weighted by A, it can be expressed as LpA, T, which is usually expressed by the symbol LpA.

Note 3. Quoted from ISO/T R25417.2007 [20], 2.3.

Single event time integral sound pressure level singleeventtime-integratedsoundpressurelevel LE the square of the sound pressure of a single, single-shot event (beep or transient) for a certain period of time T (starting at t1, ending at t2) the ratio of the integral to the reference value is taken as 10 times the logarithm of the base 10 and expressed in decibels (dB).

LE=10lg

P2(t)dt

In the formula.

E0---reference value, E0 = 20 µPa ( ) 2 s = 4 × 10 -10 Pa 2 s.

Note 1. This value can be calculated by the formula Lp, T 10lg T0 Obtained, where T0=1s.

Note 2. When used to measure acoustic illumination (see GB/T 17249.1-1998 [19]), this quantity is often referred to as the "exposed sound level" (see ISO/T R25417.2007 [20], 2.7).

Measurement time periodmeasuretimeinterval Part or multiple operating periods or operating periods used to determine the time-averaged sound pressure level of the noise source being measured.

Note. The unit of measurement time is seconds (s).

Free sound field the sound field in a uniform, isotropic medium without boundaries.

Note. In fact, the free sound field is the sound field that is negligible in the reflection of the boundary or other interfering objects within the test frequency range.

Free sound field freesoundfieldoverareflectingplane on the reflecting plane Above the infinitely reflective surface, there is no half-space free field of other obstacles.

Reflecting surface

Install the acoustic reflection plane of the noise source being measured.

Test frequency range frequencyrangeofinterest in general, the frequency range of the test includes a octave band with a center frequency of 125 Hz to 8000 Hz (for a 1/3 octave band, the center frequency the rate is 100Hz~10000Hz).

Note. For specific test purposes, the frequency range can be extended or reduced if the test environment and instrument performance are met during the rebuilt frequency range.

Minus, but the test frequency range should be indicated in the test report.

3.10

Reference body referencebox A test rig that surrounds all the main acoustic radiating components of the tested sound source and the installed sound source, and terminates in the reflection plane of the measured sound source an imaginary parallelepiped on the top.

Note. If necessary, in order to be able to measure the sound pressure level next to the noise source according to GB/T 17248.2, the test bench should be as small as possible.

3.11

Sound source feature size characteristicsourcedimension D0 the distance from the origin of the coordinate system to the farthest point of the reference body.

Note. The unit of sound source feature size is meters (m).

3.12

Measuring distance measurementdistance the distance from the reference body to the parallelepiped measuring surface.

Note. The unit of measurement distance is meters (m).

3.13

Measuring radius measurementradius the radius of the hemisphere, 1/2 hemisphere, or 1/4 hemisphere measurement surface.

Note. The unit of measurement radius is meters (m).

3.14

Measuring surface measurementsurface the area is S, which surrounds the measured sound source and arranges the imaginary plane of the sound pressure level on the microphone measuring point, which terminates in the opposite direction of the sound source.

Shooting surface.

3.15

Background noise all noise from other sources than the noise source being measured.

Note. Background noise includes air noise, structural vibration noise, and electrical noise in the instrument.

3.16

Background noise correction value backgroundnoisecorrection K1 Correction of the effect of background noise on the average (energy average) of the time-averaged sound pressure levels of all microphone positions on the measurement surface.

Note 1. The background noise correction value is expressed in decibels (dB).

Note 2. Background noise correction is related to frequency. For the frequency band, the correction value is expressed by K1f, where f is the corresponding center frequency; for A weighting, the correction value is used.

K1A said.

3.17

Environmental correction value K2 Sound reflection and sound absorption of the test environment. Average value (energy average) of the time average sound pressure level of all microphone positions on the measurement surface the correction is ringing.

Note 1. The environmental correction value is expressed in decibels (dB).

Note 2. Environmental corrections are related to frequency. For the frequency band, the correction value is recorded as K2f, where f represents the center frequency of the relevant frequency band, and is recorded under the A-weighting case.

For K2A.

Note 3. In general, the environmental correction depends on the area S of the measuring surface, and usually K2 increases as S increases.

3.18

Time averaged sound pressure level of the measuring surface surfacetime-averagedsoundpressurelevel Lp Correction of background noise K1 and environment K2 on all microphone positions on the measuring surface or continuous measurement path of the microphone the average of the time average sound pressure levels (energy average).

Note. The average sound pressure level of the measurement surface is expressed in decibels (dB).

3.19

Single event time integration sound pressure level surfacesingleeventtime-integratedsoundpressurelevel LE Correction of background noise K1 and environment K2 on all microphone positions on the measuring surface or continuous measurement path of the microphone the average value (energy average) of the sound pressure level after the surface single event time.

Note. Surface single event time integral sound pressure level is expressed in decibels (dB).

3.20

Sound power the sound power is the product of the sound pressure p at a point on the measuring surface and the normal component of the measuring surface velocity of the point particle velocity on the entire measuring surface.

integral.

[ISO 80000-8:2007 [21], 8-16]

Note 1. The unit of sound power is watts (W).

Note 2. This value is related to the acoustic energy of the air emitted by the sound source unit time.

3.21

Sound power level LW the ratio of the sound power P of the sound source to the reference value P0 is 10 times the logarithm of the base 10, expressed in decibels (dB).

LW = 10lg

In the formula.

P0---reference value, P0=1pW.

Note 1. If the specific frequency weighting specified in GB/T 3785.1 and/or the application of a specific frequency band is applied, it needs to be marked with an appropriate subscript, for example, LW A Show A weighted sound power level.

Note 2. This definition refers technically to ISO 80000-8:2007 [21], 8-23.

[ISO/T R25417.2007 [20], 2.9] 3.22 Sound energy the integral of the sound power P over a certain duration T (starting at t1, ending at t2).

J=integral

P(t)dt (5)

Note 1. The unit of acoustic energy is Joule (J).

Note 2. This amount is especially suitable for non-steady, intermittent sound events.

[ISO/T R25417.2007 [20], 2.10] 3.23 Sound energy level LJ the ratio of the acoustic energy J to the reference acoustic energy J0 is 10 times the logarithm of the base 10, expressed in decibels (dB).

LJ=10lg

In the formula.

J0---reference value, J0=1pJ.

Note. If the specific frequency weighting specified in GB/T 3785.1 and/or the application of a specific frequency band is applied, an appropriate subscript is required to indicate, for example, LJA A weighted sound energy level.

[ISO/T R25417.2007 [20], 2.11] 3.24 Apparent directivity index D*Ii A measure of how much the sound of the measured sound source radiates in the direction of the i-th microphone relative to the average of the sound radiation of the measuring surface.

D*Ii = Lpi(ST)- L'p(ST)-K1[ ] (7) in the formula.

Lpi(ST)---the time average of the i-th microphone position on the measurement surface after background noise correction (or single time) Event time integral) sound pressure level, expressed in decibels (dB);

L'p(ST)---the time average (or single event time integral) sound pressure level of all microphone positions on the measuring surface when the measured sound source is running Average value, expressed in decibels (dB);

K1 --- Background noise correction value, expressed in decibels (dB).

Note 1. The apparent directivity index is expressed in decibels (dB).

Note 2. The apparent directivity index is determined by the sound pressure level of the measured sound source corrected by background noise, but the effect of the acoustic environment is not corrected.

3.25

Apparent measurement surface sound pressure level unevenness index apparentsurfacesoundpressurelevelnon-uniformityindex V*I Measures the amount of change in the measured sound pressure level on the measurement surface.

NM-1sum

Lpi(ST)-Lpav[ ] 2 (8) in the formula.

Lpi(ST)---When the measured sound source is running, the time of the i-th microphone position on the measuring surface is corrected by the background noise (or single event) Piece time integral) sound pressure level, expressed in decibels (dB);

Lpav --- When the measured sound source is running, the background noise correction time average (or single event time product) of all the microphone positions on the measurement surface the arithmetic mean of the sound pressure level, expressed in decibels (dB);

NM --- The number of positions of the microphone.

Note 1. The apparent pressure level unevenness index of the apparent measurement surface is expressed in decibels (dB).

Note 2. When V*I is determined on a specific measurement surface of the measurement radius r or the measurement distance d, the values are expressed by V*Ir or V*Id, respectively.

Note 3. The measurement surface sound pressure level non-uniformity index is determined by the sound pressure level of the measured sound source corrected by the background noise, but the influence of the acoustic environment is not corrected.

4 Test environment