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GB/T 38979-2020 PDF in English


GB/T 38979-2020 (GB/T38979-2020, GBT 38979-2020, GBT38979-2020)
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GB/T 38979-2020: PDF in English (GBT 38979-2020)

GB/T 38979-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 91.140.70
Q 31
Sanitary wares - Test method for flushing noise of
toilet
ISSUED ON: JULY 21, 2020
IMPLEMENTED ON: JUNE 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 5 
4 Facility conditions and measuring instruments ... 5 
5 Sample installation and commissioning ... 6 
6 Sound pressure level measurement ... 7 
7 Result calculation ... 10 
8 Uncertainty of measurement ... 14 
9 Test report ... 19 
Sanitary wares - Test method for flushing noise of
toilet
1 Scope
This Standard specifies the facility conditions and measuring instruments,
sample installation and commissioning, sound pressure level measurement,
result calculation, uncertainty of measurement and test report for flushing noise
detection of toilets (not including toilets and smart toilets that use pressure
flushing devices).
This Standard applies to the flushing noise detection of toilets (not including
toilets and smart toilets that use pressure flushing devices).
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
GB/T 3768-2017, Acoustics - Determination of sound power levels and
sound energy levels of noise sources using sound pressure - Survey method
using an enveloping measurement surface over a reflecting plane
GB/T 3785.1, Electroacoustics - Sound level meters - Part 1: Specifications
GB/T 6952, Sanitary wares
GB/T 15173, Electroacoustics - Sound calibrators
GB/T 26730, Sanitary ware - Gravity water flushing devices and supports
JC/T 764, WC seats
JC/T 932, Drainage fittings for sanitary wares
ISO 3744, Acoustics - 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
Note: When it comes to the arbitration of the detection result of flushing noise
of the toilet sample, the detection result of the semi-anechoic room shall
prevail.
4.2 Measuring instruments
The sound level meter for measurement shall meet the requirements for Grade-
2 instrument in GB/T 3785.1; it is recommended to use a Grade-1 instrument.
The sound calibrator shall meet the Grade-1 accuracy requirements in GB/T
15173.
5 Sample installation and commissioning
5.1 Sample quantity and specifications
Take a toilet sample.
5.2 Toilet matching requirements
5.2.1 For matching products, install the to-be-tested toilet sample in accordance
with the manufacturer's instructions; conduct a connection tightness test under
the test static pressure of 0.14 MPa ± 0.01 MPa, to ensure that the toilet and its
flushing devices have the overall tightness in good condition.
5.2.2 For non-matching products, the to-be-tested toilet sample can be
equipped with a gravity flushing device that meets the requirements of rated
water consumption, has an anti-siphon function and meets the requirements of
GB/T 26730; the working water level of the flushing tank shall meet the needs
of the normal flushing process. The WC seats shall comply with JC/T 764. The
sanitary ware support that is used for the wall-mounted toilet sample shall meet
the requirements of GB/T 26730. Use a flange, of a suitable size, that conforms
to JC/T 932, to adjust the drainage method of the rear-row toilet sample to the
bottom delivery type. Then, perform the connection tightness test under the test
static pressure of 0.14 MPa ± 0.01 MPa, to ensure that the toilet and the flushing
devices have good overall tightness.
5.3 Installation and orientation of the toilet sample
Place the to-be-tested floor-type toilet sample or the sanitary ware support that
contains the wall-mounted toilet sample on the floor of the semi-anechoic room
or rigid-wall room; make the distance between the center and any wall not less
than 1.5 m. Adjust the actual water consumption of the sample to be less than
or equal to the nominal water consumption; fill the toilet water seal to the normal
water level. When installing the toilet sample, suitable sound insulation
measures such as rubber pads shall be used to avoid interference noise
between the sample (or sanitary ware support) and the ground during the test.
6.4.2 In the full flushing mode, take a complete normal flushing cycle as the
measurement period of the sound level meter's audio frequency signal
acquisition, from the start of the drain valve button to the close of the inlet valve.
6.4.3 Take the normal flushing cycle of the to-be-tested toilet sample as the
measurement period; use the A-weighted equivalent sound level fast-time
weighting characteristic "F" of the sound level meter to determine the A-
weighted accumulative percentage sound pressure level LpAi(B)(50) and LpAi(B)(10)
of the background noise on the hemispherical measurement surface and record
them.
6.4.4 Before testing the flushing noise of the toilet sample, it shall meet the
requirements for water consumption in GB/T 6952.
6.4.5 Under the specified test static pressure, start the flushing device and time
it in the normal way (generally no more than 1 s); use the A-weighted fast-time
weighting characteristic "F" of the sound level meter to respectively measure
the A-weighted cumulative percentage sound pressure levels LpAi(50) and LpAi(10)
of the toilet flushing noise on the hemispheric measurement surface and record
them.
Note: When a multi-channel acoustic analyzer is used for automatic audio
frequency signal acquisition, the acoustic signal acquisition time of the
instrument can be set to no more than 125 ms.
7 Result calculation
7.1 Calculation of the average value of A-weighted cumulative percentage
sound pressure level
Under normal flushing cycle conditions, the A-weighted cumulative percentage
sound pressure level average value _____ L'pA(50) and _____ L'pA(10) of the flushing noise of the
to-be-tested toilet sample are respectively calculated in accordance with
Formula (1) and Formula (2):
Where:
_____
L'pA(50) -- During the normal flushing cycle, the A-weighted cumulative 50% sound
pressure level average value of the toilet flushing noise that is measured
on the hemispherical measurement surface, in decibels (dB);
Keep one significant digit after the decimal point for the measurement results
of the A-weighted cumulative percentage sound pressure level of toilet flushing
noise and background noise LpAi(50), LpAi(10) and LpAi(B)(50), LpAi(B)(10); round the
calculation results of the average values _____ L'pA(50) , _____ L'pA(10) and ______ LpA(B)(50) , ______ LpA(B)(10) to the
nearest integer. Keep one significant digit after the decimal point for the
calculation results of the background noise correction value K1A(50), K1A(10) and
the environmental correction value K2A of the A-weighted cumulative
percentage sound pressure level; round the calculation results of the A-
weighted sound power level LWA(50) and LWA(10) to the nearest integer.
8 Uncertainty of measurement
8.1 Combined standard uncertainty uLWA of the A-weighted sound power
level measurement
The uncertainty uLWA of the toilet flushing noise sound power level that is
measured according to this Standard is characterized by its total standard
deviation σtot; it’s calculated according to Formula (12):
Where:
uLWA -- uncertainty of sound power level, in decibels (dB);
σtot -- total standard deviation, in decibels (dB);
σR0 -- reproducibility standard deviation of the measurement method, in
decibels (dB);
σomc -- standard deviation of the uncertainty that is caused by the installation
and test conditions of the to-be-tested toilet sample, in decibels (dB).
8.2 Determination of σomc
Under the test static pressure of 0.14 MPa ± 0.01 MPa, the same standard test
operator uses the same sound level meter, and, according to the test
procedures that are specified in Chapter 6, uses the point that is numbered 10
on the hemispheric measurement surface as the microphone position
coordinate, to perform at least 6 repeated measurements of the A-weighted
cumulative percentage sound pressure level average values _____ L'pA(50) and _____ L'pA(10) of
the flushing noise of the same toilet sample that is installed at the same position
in the test room (The toilet needs to be re-installed before each measurement),
and corrects the background noise for the measurement results.
8.3.2 Uncertainty caused by the measurement method
Assume that the uncertainty components in this Standard are not related to
each other, and the modeling method is complete and correct, then, the method
uncertainty that is caused by the residual uncertainty is umethod = 0.6 dB, and
the sensitivity coefficient is cmethod = 1.
8.3.3 Repeatability standard deviation of sound pressure level
measurement
Under the test static pressure of 0.14 MPa ± 0.01 MPa, the same standard test
operator uses the same sound level meter, and, according to the test
procedures that are specified in Chapter 6 of this Standard, uses the point that
is numbered 10 on the hemispheric measurement surface as the microphone
position coordinate, to perform multiple times (at least 6 times) of repeated
measurements of the A-weighted cumulative percentage sound pressure level
average values _____ L'pA(50) and _____ L'pA(10) of the flushing noise of the same toilet sample
that is installed at the same position in the test room (The sound level meter
needs to be repositioned before each measurement).
The uncertainty of the measured value uL'pA(50) and uL'pA(10), namely their
standard deviations sL'pA(50) and sL'pA(10), are calculated according to Formula
(16) and Formula (17) respectively; the upper limit is not more than 1.5 dB.
Where:
L'pA(50),j -- toilet flushing noise A-weighted cumulative 50% sound pressure level
of the jth repeated measurement, in decibels (dB);
L'pA(50)av -- arithmetic average of all repeated measurement results of L'pA(50),j, in
decibels (dB);
L'pA(10),j -- toilet flushing noise A-weighted cumulative 10% sound pressure level
of the jth repeated measurement, in decibels (dB);
L'pA(10)av -- arithmetic average of all repeated measurement results of L'pA(10),j, in
decibels (dB).
The sensitivity coefficients cL'pA(50) and cL'pA(10) of the measured value are
calculated according to Formula (18) and Formula (19) respectively:
issued by its calibration certificate; the corresponding sensitivity coefficient is
cslm = 1.
8.3.9 Uncertainty caused by the number of limited measurement points
The uncertainty which is introduced by the number of limited measurement
points umic is calculated according to Formula (22) and Formula (23); the
corresponding sensitivity coefficient is cmic = 1.
Where:
NM -- number of microphone positions;
L'pA(50)av -- arithmetic average of the measured values of L'pAi(50), in decibels (dB);
L'pA(10)av -- arithmetic average of the measured values of L'pAi(10), in decibels (dB).
8.3.10 Uncertainty caused by the angle difference between the sound
source acoustic emission direction and the measurement surface normal
In a semi-anechoic room, the uncertainty which is caused by the angle
difference between the acoustic emission direction of the toilet flushing noise
and the hemispherical measurement surface normal is uangle = 0.25 dB; the
sensitivity coefficient is cangle = 10-0.1K2A. For a rigid-walled room, it is
recommended to analyze the influence of the sound source and its directivity,
measurement distance and other factors to determine the standard uncertainty
reasonably.
8.3.11 Uncertainty caused by the frequency spectrum shape and tuned
sound
Since there is no audible tuned sound in the toilet flushing process, it can be
assumed that the uncertainty which is introduced by the frequency spectrum
shape and tuned sound is utone = 0 dB; the sensitivity coefficient is ctone = 1.
8.4 Extended uncertainty of measurement U
The extended uncertainty of measurement U is calculated according to Formula
(24):
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.