Acoustics-Measurement of sound attenuation of hearing protectors-Subjective method
Some standard content:
1 Introduction
National Standard of the People's Republic of China
Acoustics-Mesurement of spand attenuatonof hearing protectorsSubjectivt methodUDC 534.833.5
: 614.892
GB7584-—87
1.1 This standard specifies the objective judgment measurement method for determining the sound attenuation of ear defenders by auditory interpretation. It can compare the sound attenuation performance data obtained under similar conditions, and can also sort and grade various types of ear defenders according to the sound attenuation, so that users can choose according to their needs, and can evaluate the structural features and designs that have a significant impact on performance. 1.2 This standard refers to ISQ 4869-1981 "Acoustics-Measurement of sound attenuation of ear defenders-Subjective method" 2 Terms and terms
2.1 Ear defenders
Equipment that protects the human ear and avoids excessive noise stimulation. Ear protectors include earplugs, earplugs, helmets, etc. Standard: Ear protectors may also include electronic devices for communication (such as the most common headphones) or some devices that can reduce the noise level between the ear protectors and the eardrum.
2.2 Ear wings
A type of ear protector, which consists of a ring shell pressed against each auricle, or an earmuff shell that surrounds the auricle and fits tightly against the head to cover the ears. The earmuff shell can be attached to the head with a special head ring or collar ring, or with the help of devices attached to a helmet or other equipment.
2.3 Ear protectors
Are ear protectors that are inserted into the ear canal, or on the outer contour to block the entrance to the external auditory canal. 2.1 Helmets
Refers to an ear protector that covers a considerable part of the head. 2.5 Hearing level
The hearing level of a person's ear refers to the hearing level expressed in hearing level measured at a specified frequency with a specified type of headphones and in a specified manner. 2.6 Hearing level
The hearing level of a person's ear refers to the minimum sound pressure level that can correctly cause hearing more than half of the times in multiple repeated tests under specified conditions with a specified sound signal.
Method: The standard used in this standard is the measurement results of wearing and not wearing ear protectors. The former is also called mutual hearing. The latter is also called mutual hearing. 2.7 Ear protector sound attenuation
Under a given test signal, the average decibel value of the difference in hearing thresholds of all subjects when wearing and not wearing ear protectors. Note: In order to distinguish it from the measurement results of the observation method, it is also called true ear sound attenuation. 2.8 Pink noise
Noise with a continuous and smooth spectrum when measured with a bandwidth proportional to the frequency. Note: Its sound pressure spectrum density is inversely proportional to the stutter rate. 2.9 Audiogram
Measured under specified conditions and methods, the relationship between the hearing level and frequency of the test ear is expressed in the form of a graph or table. Approved by the National Bureau of Standards on March 27, 1987
Implementation on November 1, 1987
3 Measurement method for sound attenuation of ear defenders
3.1 Test signal
GB7584-87
3.1.1 The test signal is the signal after pink noise passes through the 1/3 octave filter of the following center frequencies. The filter characteristics should meet the requirements of GB3241-82 "1/1 and 1/3 octave filters for sound and vibration analysis". 63Hz (optional)
1000Hz
2000HzWww.bzxZ.net
3150Hz (optional)
4000Hz
6300Hz (optional)
8000Hz
Note: If the amplifier under test is considered to have a large attenuation change with frequency, the frequency of the test signal should be increased and the test should be carried out according to the relevant one-fold frequency band center frequency
. The center frequency should be selected according to GB 3240-82 "Usable frequency in acoustic measurement". 3.1.2 In order to facilitate identification, the test signal should be intermittent, 1 to 2 times per second, the signal duration and interval should be roughly equal, and no other noise should be heard during the transition period. a.2 Test location
3.2.1 The ideal test location should be a random sound field, which reflects the effect of use under active conditions. This sound field is approximately achieved when the sound field meets the following requirements: The midpoint of the line connecting the two ear canal openings of the subject is specified as the reference point, and the sound pressure level measurement is carried out at six positions with an omnidirectional microphone without the subject present. These positions are 15 cm away from the reference point on the "front-back" axis, the "left-right" axis, and the "up-down" axis. The maximum tolerance of the sound pressure level relative to the reference point is X+2.5dB, and the difference between the left-right positions should not exceed 3dB. For the test frequency band with a center frequency greater than or equal to 500Hz, the difference in the sound pressure level of any two directional incident sound waves measured at the reference point should not be greater than 5 dB.
Note: This measurement can only be carried out when using a very directional microphone. After using some suitable directional microphones, the measured sound field changes may be small. Table 1 shows the relationship between the sensitivity index (an index expressing the directivity of the microphone) of the normal incident relative to the random incident and the measured sound field changes. Table 1
Sensitivity index of normal radiation relative to random radiation dB
Measured sound field change
This microphone is suitable for
GB 7584-87
To achieve the required sound field, more than one (multiple) loudspeakers can be used in the test room. If several loudspeakers are used to produce the desired sound field, it is necessary to feed the loudspeakers with non-phase electrical signals to eliminate standing waves and other interference effects. If a reverberation chamber is used as the test room, its inherent acoustic time band - reverberation time must be determined so that it does not interfere with the rise time and fall time of the test signal specified in IEC
645 "Audiometer". 3.2.2 When the subject is not present, the background noise at the measuring point in the test space shall not exceed the values given in Table 2. Whether the central noise level meets the value given in Table 2 can be determined by the following two methods: Method A: Directly measure the sound pressure level to determine the background noise level. Method B: Sixth-frequency band sound pressure level (reference sound pressure is 20uPa) Under the condition of sound attenuation test, at least three hearing readings are measured to be better than the hearing readings of normal subjects. If the hearing readings at each test frequency for each center frequency listed in 3.1 are not greater than or equal to the values listed in Table 2, the background noise of this test space can be considered appropriate. 3.2.3 Any audible noise in the test space will cause masking of a part of the test frequency, increasing the error of the hearing. If the test room cannot always meet the specified room background noise, it is advisable to select the time when the noise is the smallest. In such cases, the background noise requirements for the minimum test band with a center frequency of 12Hz should be as low as and including 6311Hz, and for the minimum test band with a center frequency of Hz, the background noise requirements should be as low as and including 31.5Hz. GB7584-87
If the subject hears external noise, a certain signal should be used to notify the audiometer and stop the test. 3.3 Test equipment
3.3.1 The test equipment should be able to generate a certain frequency range of test signals at the test point: from 112Hz (the lower limit frequency of the 125Hz-octave band) (or 56Hz if the center frequency of the test band is 63Hz) to 900jHz (the upper limit frequency of the 8000Hz octave band). The loudspeaker system included in this equipment should be able to produce the minimum and maximum test signal pressure levels required in Table 3 at the subject's position. Table 3
Centre frequency
Minimum and maximum test signal octave band pressure levels
(maximum sound pressure 20μPa)
- 10 ~ 70
- 15 ~ 70
- 2 ~ 80
- 20 ~ 80
The distortion factor of this equipment, including the loudspeaker system, shall ensure that the test signal can be reliably reproduced without any crackling or humming in each test frequency band and level listed in Table 3. For a test signal, the maximum sound pressure level in all octave bands other than the test frequency band and the two bands directly above and below shall be at least 40dB lower than the average sound pressure level of the test frequency signal to meet this requirement. The time weighting characteristic of the "fast gear" (F) is used for the measurement. 3.3.2 The attenuator step is 2.5dB or less. 3.3.3 When calibrating the whole test equipment including the sound sensor, the error of the difference between the readings at any two positions shall not exceed 2dB within the full range of the attenuator. Calibration is carried out according to the method of calibration. Outside the range that can be calibrated by the method of calibration, the signal voltage at the sound sensor terminal can be measured by an electric measuring instrument to check the test equipment. In the attenuation system of the test equipment, when the required accuracy cannot be achieved, the test equipment should be calibrated: the correction value obtained should be added to the measurement result.
3.3.4 Any transient phenomenon caused by the signal switching should be consistent with the requirements of IE645 "Audiometer". 3.4 Subjects
$.4.1 The test subjects shall meet the following conditions; according to the audiometer test results, the difference between the two hearings is not more than 10dB, and the hearing level does not exceed 15dB at a frequency less than or equal to 2000Hz, and does not exceed 25dB at a frequency greater than 12000Hz. All hearing levels are determined according to the standard equivalent hearing pressure level of GB4854-84 "Standard Zero Level for Calibration of Pure Tone Audiometers". If the background noise in the test room is the minimum sound pressure level listed in Table 2, the subjects whose hearing level is less than 10dB will be eliminated. 3.4.2 The subjects selected shall not be selected regardless of the size and shape of their heads and ears unless there are obvious abnormalities that affect the fitting of the ear protectors.
3.4.3 Before the formal test, each subject shall be given practical training. At the end of the practical course, at least two complete audiograms of the test signals listed in Article 3.1 shall be recorded for each subject. In these two audiograms, the difference in hearing level at each corresponding frequency within the frequency range of 250Hz to 4000Hz shall not exceed 6B. 3.4.4 For each test, at least ten subjects who meet the requirements of Articles 3.4.1, 3.4.2 and 3.4.3 shall be selected. 3.5 Test steps
GB 7584-87
3.5.1 Each subject can be tested multiple times, but the number of tests for each subject should be the same, and the number of repeated tests should be reported to the other party.
8.5.2 The test environment and test steps should be informed to the subject in detail. The audiometer should guide each subject to wear the ear protector according to the manufacturer's instructions. If it is available in several sizes, the audiometer should help each subject to choose the ear protector of the right size. After the subject has received appropriate instructions, the ear protector must be put on by the subject.
Note: The ear protector should be worn in the normal position during the test. When using this standard, avoid wearing glasses, earrings or other situations that may reduce the sealing performance of this device.
The fit of the earmuffs worn by the subjects is adjusted to the best state under the following conditions. After wearing the earmuffs, a wide frequency noise is emitted to make the total sound pressure level at the subject's position reach 60-80dB (the reference sound pressure is 20μPa). The subjects are instructed to adjust the earmuffs by hand until they feel the best sound attenuation effect, and at the same time, they must ensure that the subjects are comfortable when wearing them. Before finally putting on the earmuffs for the formal test, the subjects should open and close their mouths and move their heads up and down and left and right several times at the same time. During the test phase, any manipulation of the earmuffs is prohibited. 5. When using earmuffs, the clamping force can be measured with an appropriate device. When doing this measurement, the distance between the two opposite sides of the earmuff gasket should be 145mm. At this time, the headband is adjusted to 129m*. This size is the distance from the center of the headband (inner surface) to the point where the center of the two ear wings is connected. The headband remains free during the measurement, and the unit of the measured force is Newton (N). 3.5.4 During the formal test, the hearing thresholds with and without ear extensions shall be measured in accordance with the recognized audiometric technique. If the test is conducted in accordance with the provisions of this standard, the occurrence of abnormal phenomena (which may be caused by insufficient understanding of this method and fatigue, etc.) can be minimized.
, 5.5 At least two pairs of ear protectors manufactured according to the specified size shall be used alternately during this test. 3.5.6 The minimum number of samples to determine the hearing threshold (naked ear or closed ear) shall be no less than ten for each test number. 4 Expression of results
The following information shall be stated in the report:
- Type of ear protector, replaceable parts of the protector shall be explained. - Number of subjects and number of repeated tests in the final formal test. Age, gender and method of selecting subjects. Method used to determine the changes in the sound field and background noise in the test room. In the final formal test, the statistical data obtained by measuring the sound attenuation of each subject under various conditions, and the mean and standard deviation. Individual results, median values, appropriate percentages and range limits may also be included in the report. In the calculation, the data of all subjects should be combined.
If it is earmuffs, the clamping force data should be available. When the attenuation characteristics are presented graphically, the provisions of GR3769-83 "Scale and size for drawing frequency curves and frequency-standard graphs" should be followed, and 50dB per 10 grids should be selected. The attenuation scale on the graph should point downward. * For some product types, such as headbands that cut behind the neck or hit under the chin, other sizes may be more suitable. The actual size should be listed together with the clamping force data.
Additional remarks:
GB 7584-87
This standard was reviewed and approved by the National Technical Committee for Standardization of Acoustics. National Technical Committee for Standardization of Acoustics
Main member: Ma Daxian; Deputy members: Jinrensheng, Xu Weiyi, Yu Han. This standard was proposed by the Subcommittee on Basic Acoustics. The Southern Learning Foundation Subcommittee
Chairman: Ma Daxian, Vice Chairman: Wu Wenqiu. The main drafters of this standard are Shang Jiqing and Zhong Xiangzhang.4 During the formal test, the hearing thresholds with and without earphones shall be measured according to the recognized audiometric technique. If the test is conducted in accordance with the provisions of this standard, the occurrence of abnormal phenomena (which may be caused by insufficient understanding of this method and fatigue, etc.) can be minimized.
, 5.5 At least two pairs of ear protectors manufactured according to the specified size shall be used alternately during this test. 3.5.6 The minimum number of samples to determine the hearing threshold (naked ear or closed ear) shall be no less than ten times for each test number. 4 Expression of results
The following information shall be stated in the report:
- Type of ear protector, replaceable parts of the protector shall be explained. - Number of subjects and number of repeated tests in the final formal test. Age, gender and method of selecting subjects. Method used to determine the changes in the sound field and background noise in the test room. In the final formal test, the statistical data obtained by measuring the sound attenuation of each subject under various conditions, and the mean and standard deviation. Individual results, median values, appropriate percentages and range limits may also be included in the report. In the calculation, the data of all subjects should be combined.
If it is earmuffs, the clamping force data should be available. When the attenuation characteristics are presented graphically, the provisions of GR3769-83 "Scale and size for drawing frequency curves and frequency-standard graphs" should be followed, and 50dB per 10 grids should be selected. The attenuation scale on the graph should point downward. * For some product types, such as headbands that cut behind the neck or hit under the chin, other sizes may be more suitable. The actual size should be listed together with the clamping force data.
Additional remarks:
GB 7584-87
This standard was reviewed and approved by the National Technical Committee for Standardization of Acoustics. National Technical Committee for Standardization of Acoustics
Main member: Ma Daxian; Deputy members: Jinrensheng, Xu Weiyi, Yu Han. This standard was proposed by the Subcommittee on Basic Acoustics. The Southern Learning Foundation Subcommittee
Chairman: Ma Daxian, Vice Chairman: Wu Wenqiu. The main drafters of this standard are Shang Jiqing and Zhong Xiangzhang.4 During the formal test, the hearing thresholds with and without earphones shall be measured according to the recognized audiometric technique. If the test is conducted in accordance with the provisions of this standard, the occurrence of abnormal phenomena (which may be caused by insufficient understanding of this method and fatigue, etc.) can be minimized.
, 5.5 At least two pairs of ear protectors manufactured according to the specified size shall be used alternately during this test. 3.5.6 The minimum number of samples to determine the hearing threshold (naked ear or closed ear) shall be no less than ten times for each test number. 4 Expression of results
The following information shall be stated in the report:
- Type of ear protector, replaceable parts of the protector shall be explained. - Number of subjects and number of repeated tests in the final formal test. Age, gender and method of selecting subjects. Method used to determine the changes in the sound field and background noise in the test room. In the final formal test, the statistical data obtained by measuring the sound attenuation of each subject under various conditions, and the mean and standard deviation. Individual results, median values, appropriate percentages and range limits may also be included in the report. In the calculation, the data of all subjects should be combined.
If it is earmuffs, the clamping force data should be available. When the attenuation characteristics are presented graphically, the provisions of GR3769-83 "Scale and size for drawing frequency curves and frequency-standard graphs" should be followed, and 50dB per 10 grids should be selected. The attenuation scale on the graph should point downward. * For some product types, such as headbands that cut behind the neck or hit under the chin, other sizes may be more suitable. The actual size should be listed together with the clamping force data.
Additional remarks:
GB 7584-87
This standard was reviewed and approved by the National Technical Committee for Standardization of Acoustics. National Technical Committee for Standardization of Acoustics
Main member: Ma Daxian; Deputy members: Jinrensheng, Xu Weiyi, Yu Han. This standard was proposed by the Subcommittee on Basic Acoustics. The Southern Learning Foundation Subcommittee
Chairman: Ma Daxian, Vice Chairman: Wu Wenqiu. The main drafters of this standard are Shang Jiqing and Zhong Xiangzhang.
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