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GB/T 33620-2017 (GBT33620-2017)

GB/T 33620-2017_English: PDF (GBT 33620-2017, GBT33620-2017)
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BASIC DATA
Standard ID GB/T 33620-2017 (GB/T33620-2017)
Description (Translated English) Textiles -- Testing and evaluation of sound absorption property
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard W04
Classification of International Standard 59.080.30
Word Count Estimation 10,174
Date of Issue 2017-05-12
Date of Implementation 2017-12-01
Quoted Standard GB/T 6529; GB/T 8170; JJG 176
Proposing organization China Textile Industry Federation
Issuing agency(ies) General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, China National Standardization Administration Committee
Summary This standard specifies the test method and evaluation of sound absorption performance of textiles. This standard applies to all kinds of fabrics and their products.

Standards related to: GB/T 33620-2017

GB/T 33620-2017
GB
NATIONAL STANDARD OF
THE PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.30
W 04
Textiles - Testing and evaluation
of sound absorption property
ISSUED ON. MAY 12, 2017
IMPLEMENTED ON. DECEMBER 1, 2017
Issued by. General Administration of Quality Supervision, Inspection
and Quarantine;
Standardization Administration Committee.
3. No action is required - Full-copy of this standard will be automatically &
immediately delivered to your EMAIL address in 0~60 minutes.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Principle... 5 
5 Equipment ... 5 
6 Standard atmosphere for conditioning and testing ... 7 
7 Specimen preparation ... 7 
8 Test procedures ... 7 
9 Results calculation and expression ... 9 
10 Evaluation on sound absorption performance ... 9 
11 Test report ... 9 
Annex A (Informative) Calculation principle of sound absorption coefficient .. 11 
Foreword
This Standard was drafted in accordance with the rules given in GB/T
1.1-2009.
This Standard was proposed by China Textile Industry Federation.
This Standard shall be under the jurisdiction of National Technical Committee
on Textiles of Standardization Administration of China (SAC/TC 209).
The drafting organization of this Standard. Guangzhou Fiber Products Testing
and Research Institute.
Main drafters of this Standard. Luo Shengli, Zhang Peng, Tan Weixin, Liao
Yinlin, Zhou Lijie.
Textiles - Testing and evaluation
of sound absorption property
1 Scope
This Standard specifies the testing method and evaluation for sound
absorption property of textiles.
This Standard applies to textiles and their products, irrespective of material.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including
any amendments) applies.
GB/T 6529, Textiles - Standard atmospheres for conditioning and testing
GB/T 8170, Rules of rounding off for numerical values & expression and
judgement of limiting values
JJG 176, Verification Regulation of Sound Calibrators
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 sound absorption property
a performance of sound energy decay when sound waves go through a
certain medium or incident surface of some medium, generally characterized
by sound absorption coefficient
3.2 random noise
sound oscillation of which the instantaneous values can not be
pre-determined; the distribution of the instantaneous value of random noise to
time is only subject to a certain statistical distribution
[GB/T 3947-1996, Definition 2.12]
3.3 sound pressure; p
the difference between medium pressure and static pressure when there is
sound wave
NOTE. The unit is Pascal (Pa).
[GB/T 3947-1996, Definition 2.21]
3.4 plane wave
vertical plane wave of which the wave front is parallel to the spread direction
[GB/T 3947-1996, Definition 4.5]
3.5 sound absorption coefficient at normal incidence; α
the ratio of normal incidence plane wave into specimen power to incident
sound power
[GB/T 18696.2-2002, Definition 3.1]
4 Principle
Mount the specimen on one end of the impedance tube and the other end is a
random noise source. The resulting plane wave is incident perpendicularly to
the surface of the specimen. Measure the sound pressure by using two
microphones on a fixed position. Calculate the sound absorption coefficient at
normal incidence of the specimen based on the sound transfer function. The
sound absorption performance of the sample shall be characterized by sound
absorption coefficient.
NOTE. See Annex A for calculation principle of sound absorption coefficient.
5 Equipment
5.1 Equipment composition
The testing equipment for sound absorption property consists of signal
generator, power amplifier, speaker, impedance tube, specimen tube,
microphone, frequency analyzer, sound calibrator. The schematic diagram of
testing device is shown in Figure 1.
Connect the test device as shown in Figure 1. Select the diameter of the test
impedance tube according to the test frequency range. Boot up for at least 10
min. The total sound pressure level of the microphone position shall be
between 90dB ~ 110dB.
8.2 Microphone calibration
Turn on the sound calibrator power switch. Select Channel 1. Insert the
corresponding No. 1 microphone into the sound calibrator for calibration.
When the number of inputs in the input signal prompt is the same as the set
calibration signal, the calibration of No. 1 microphone shall be completed.
Follow the steps above to complete the calibrations for other microphones.
8.3 Specimen installation
Install the specimen in the test tube. Slowly push the metal rod of the sleeve
to make the surface of the sound of the specimen flush with the contact face.
It shall ensure that the specimen is fully filled into the cavity of the test tube. In
order to prevent the sound leakage, the gap around the specimen shall be
blocked with Vaseline and other grease. If necessary, double-sided tape can
be used to firmly adhere the specimen to the back plate of the resistance tube
to prevent vibration or excess air. For test specimens that require an air layer
thickness, the metal rods of the sleeve shall be drawn to the desired air layer
thickness.
8.4 Correction of microphone mismatch
Using the exchange channel to repeat the measurement to complete the
microphone mismatch correction. Insert the microphone connected to
Channel 1 into the slot near the speaker. Insert the microphone connected to
Channel 2 into the slot near the specimen. Click the button to start the
measurement. After the commissioning is passed, switch the position of the
two microphones, that is, the microphone connected to the Channel 1 is
inserted in the slot near the specimen, and the microphone connected to the
Channel 2 is inserted in the slot near the speaker. Click the button to start the
measurement, then the microphone mismatch correction shall be completed.
8.5 Sound absorption coefficient test
After the mismatch correction of the microphone is completed, the two
microphones shall be returned to the initial position, and the sound absorption
coefficient test shall be carried out. The sound absorption coefficient shall be
recorded according to the different frequencies. Similarly, according to steps
8.3 ~ 8.5 to complete the remaining two groups of specimens of the sound
absorption coefficient test.
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