JJG 188-2017 English PDF (JJG188-2017)

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JJG 188-2017: Sound Level Meters
JJG 188-2017
JJG
METERING and VERIFICATION REGULATION
OF THE PEOPLE’S REPUBLIC OF CHINA
Sound level meters
声级计
ISSUED ON: NOVEMBER 20, 2017
IMPLEMENTED ON: MAY 20, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People‘s Republic of China.
Table of Contents
Introduction ... 5
1 Scope ... 7
2 References ... 7
3 Terms and measurement units ... 8
4 Overview ... 16
5 Metrological performance requirements ... 16
5.1 Indication sound level adjustment ... 16
5.2 Frequency weighting ... 17
5.3 Frequency weighting at 1kHz ... 19
5.4 Level linearity ... 19
5.5 Self-generated noise ... 20
5.6 Time weightings F and S ... 20
5.7 Toneburst response ... 21
5.8 Repeated toneburst response ... 22
5.9 Overload indication ... 23
5.10 C-weighted peak sound level ... 23
6 General technical requirements ... 24
6.1 Marking... 24
6.2 Functional inspection ... 24
7 Measuring instrument control ... 24
7.1 Verification conditions ... 25
7.2 Verification items ... 26
7.3 Verification method ... 27
7.4 Processing of verification results ... 38
7.5 Verification cycle ... 38
Appendix A Maximum allowable measurement uncertainty ... 39
Appendix B Other methods for frequency weighted acoustic signal testing ... 40
Appendix C Inner page format of the verification certificate and verification result
notice ... 43
Verification regulation of sound level meters
1 Scope
This Regulation applies to the initial verification, subsequent verification, in-use
inspection of time-weighted sound level meters, integral average sound level meters,
integrating sound level meters that meet the requirements of IEC 61672-1.
2 References
This Regulation makes reference to the following documents:
JJG 176-2005 Verification regulation of sound calibrators
JJG 482-2005 Verification regulation of laboratory standard microphones (free-field
reciprocity method)
JJG 790-2005 Verification regulation of laboratory standard microphones (coupler
reciprocity method)
JJG 1019-2007 Verification regulation of working standard microphones (coupler
comparison method)
JJF 1001-2011 General terms in metrology and their definitions
JJF 1034-2005 Metrological terms and their definitions for acoustics
JJF 1147-2006 Verification specification for acoustic performance of anechoic
rooms and hemi-anechoic rooms
JJF 1293-2011 Verification specification for electrostatic actuators
GB/T 3102.7 Quantities and units of acoustics
GB/T 3947-1996 Acoustical terminology
GB/T 17312 Random-incidence and diffuse-field verification of sound level meters
IEC 61672-1:2013 Electroacoustics - Sound level meters - Part 1: Specifications
IEC 61672-2:2013 Electroacoustics - Sound level meters - Part 2: Pattern evaluation
tests
IEC 62585 Electroacoustics - Methods to determine corrections to obtain the free-
sound level meter shall not exceed ±1.1 dB. When the input signal level changes
arbitrarily by 1 dB ~ 10 dB, the same change in the sound level indication shall be
caused. The measured deviation from the design target shall not exceed ±0.3 dB for
Class 1 sound level meters and ±0.5 dB for Class 2 sound level meters.
5.4.3 In all level ranges of the nominal A-weighted sound level, C-weighted sound level,
Z-weighted sound level provided, the Class 1 sound level meter shall at least measure
31.5 Hz, 1 kHz, 4 kHz, 8 kHz, 12.5 kHz; the Class 2 sound level meter shall at least
measure 31.5 Hz, 1 kHz, 4 kHz, 8 kHz according to the upper and lower boundaries of
the linear working range given in the instruction manual.
5.4.4 For the frequencies specified in 5.4.3, the starting point of the linear measurement
given in the instruction manual in the specified level range shall be used for
measurement. The starting point at 1 kHz shall be the reference sound pressure level.
5.5 Self-generated noise
5.5.1 The sound level meter shall be set to the most sensitive level range and placed in
a low noise sound field, that will not cause an increase in self-generated noise. The
sound level meter now indicates the self-generated noise level. These sound levels shall
be the highest expected self-generated noise levels for the various types of microphones
used by the sound level meter.
5.5.2 For all frequency weightings, the self-generated noise level can be given by the
time-weighted sound level or the time-averaged sound level.
5.5.3 For all frequency weightings, measure the highest expected self-generated noise
when the microphone is replaced by an electrical input device, using the input method
given in the instruction manual.
Note: The indication of the sound level meter is affected by background noise as well as self-
generated noise. The self-generated noise level is reported only as information and is not used
to determine compliance. The reported self-generated noise level does not require an associated
uncertainty.
5.6 Time weightings F and S
5.6.1 The design target for the exponential time constant of the sound level meter time
weighting F is 0.125 s and the time weighting S is 1 s. The decay rate of the indicated
sound level shall be measured by suddenly terminating the input 4 kHz steady-state
sinusoidal electrical signal. The decay rate of the time weighting F shall be between
31.0 dB/s and 38.5 dB/s; the time weighting S shall be between 3.6 dB/s and 5.1 dB/s.
5.6.2 At the reference sound pressure level within the reference level range of the sound
use inspection.
7.1 Verification conditions
7.1.1 Environmental conditions
The verification environmental conditions of the sound level meter are as follows:
- Temperature: (23 ± 3) °C;
- Relative humidity: (30 ~ 90)%;
- Static pressure: (97 ~ 103) kPa.
7.1.2 Reference environmental conditions
The reference environmental conditions of the sound level meter are as follows:
- Temperature: 23 °C;
- Relative humidity: 50%;
- Static pressure: 101.325 kPa.
Note: When the air pressure at the location of the measurement laboratory cannot meet the
above requirements, the verification of the frequency weighting must be corrected. If no
correction data is available, when the air pressure is higher than 80 kPa and less than 97 kPa,
the laboratory shall add a standard uncertainty of 0.09 dB at frequencies not greater than 3
kHz, or a standard uncertainty of 0.14 dB at frequencies greater than 3 kHz. The actual
measurement expansion uncertainty shall not exceed the corresponding maximum
allowable measurement uncertainty in Appendix A.
7.1.3 Measurement standards and main supporting equipment
a) Sound calibrator: The performance level shall comply with level 1 specified in
JJG 176-2005.
b) Reference microphone: A laboratory standard microphone that meets the
requirements of JJG 790-2005 or JJG 482-2005.
c) Audio signal generator: The frequency range is 10 Hz ~ 20 kHz; the frequency
error shall not exceed ±0.25%; the total distortion of the output signal is not more
than 0.1%.
d) Measuring amplifier: The frequency range is 10 Hz ~ 20 kHz; the frequency
response shall not exceed ±0.2 dB; the total distortion shall not exceed 0.3%.
e) Preamplifier: The frequency response shall not exceed ±0.1 dB within the
verification frequency range; the linear short-circuit noise at the input end shall
not exceed 10 μV; the A-weighted short-circuit noise shall not exceed 3 μV.
f) Burst tone signal generator: It can output signals that meet the requi...