Issues on inspection of audiometric room

Transcription

1 Issues on inspection of audiometric room

2 1 Abstract 2 3 4

3 1 Abstract 2 3 4

4 1 Introduction of the audiometric room Application scope: The pure tone hearing test in CDC (Center for disease Control and Prevention) and ODPC (Occupational Disease Precaution Clinic). Outpatient hearing diagnosis center in hospitals. Hearing monitoring and diagnose in ENT department (ear-nose-throat ). Hearing screening room in CDC and ODPC.

5 Audiometric room Three elements Qualified detection personnel Qualified testing instrument Standard test environment Basic requirement for audiometric room

6 Audiometric room

7 Test environment must be well ventilated (usually small audiometric room needs ventilate 6~10 times per hour) Suitable temperature and humidity (e.g. 18 ~22, and RH 40%~60%)

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9 1 Abstract 2 3 4

10 2 Measurement parameter of audiometric room 2.1 Domestic criterion in audiometric room

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12 2.2 Environment Condition Temperature :(18~28) Relative humidity : (30~90)% Atmospheric pressure : (86~106)k Pa

13 2.3 Main Test Equipment Names of Equipment Model Measurement Range Manufacturer Condenser microphone Hz~20kHz Bruel & Kjaer Preamplifier Hz~20kHz Bruel & Kjaer Low noise microphone unit Hz~20kHz Bruel & Kjaer Acoustic calibrator dB 114.0dB Bruel & Kjaer Standard source Hz~10kHz Bruel & Kjaer Pulse audio analyzer 3560-B-T04 20Hz~25.6kHz Bruel & Kjaer Hemispherical non directivity source Nor275 50Hz~20kHz Nornic

14 2.4 Audiometric room calibration Basic description Cable sealing pipe ends Indoor ventilation The structure and seal situation of the soundproof door

15 Sounder Using pure tone, FM, narrow-band noise or recorded language materials as audiometry threshold test signal. To ensure the measurement accuracy and reproducibility,the subjects should be tested in the frequency range between 125Hz~12.5k Hz.

16 2.4.1 Background noise measurement The block diagram of background noise measurement

17 Ear headphones The maximum sound pressure level of the background noise allowed in Audiometric room

18 Bone vibrator The maximum sound pressure level of the background noise allowed in Audiometric room

19 Speaker The maximum sound pressure level of the background noise allowed in Audiometric room

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21 2.4.2 Measurement of sound field in audiometric room Quasi-free field Diffusion field

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23 Microphone placement Quasi-free field Quasi-free field: The sound pressure level at any point can not exceed 2dB

24 Microphone placement Free field Free field: the test microphone should be put at 0.1m both in front and back of the reference point to measure the SPL.

25 Deviation between sound pressure level attenuation and inverse square law of sound pressure level in the free field SPL of r 1 and r 2 should not exceed ±1dB due to sound pressure attenuation and inverse square law.

26 Microphone placement Diffusion field The SPL deviation between reference point and other test points should not exceed ± 2.5dB. At the same time the SPL difference between the left and right point should not exceed 3dB.

27 The difference SPL of diffusion field

28 1 Abstract 2 3 4

29 The sound insulation effect of audiometric room is the key point in designing of the audiometric room. It must conform to related standards of environment noise.

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31 3 Definition of sound insulation

32 Apparent Sound Pressure Sound Insulation(ASPSI):the difference SPL between the cabins laboratory external and internal in reverberation sound field. The sound field in the room may not be a diffuse sound field.

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34 3.1 Test method for sound insulation

35 Note: The fixed microphone measure each point at least 5 times. When the center frequency is below 400Hz, the average time of recording should not less than 6s at each point. The average time can t less than 4s when the frequency is higher than 400Hz.

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37 The position of microphones in audiometric room Use at least five microphones to measure the average SPL

38 Taking three speakers for example, the distance between two speakers should keep at least 3m, and speakers position should be distributed evenly in audiometric room. Each distance between the microphone and the speaker should keep more than 2 m.

39 The SPL measured from microphones should be the mean value of energy When use three microphones, the positions should be distributed in the sphere whose center is on the reference point with radius of 0.3m. The distance between the microphone and the indoor wall should exceed 0.2*d, that d is the shortest internal dimensions of audiometric room. All microphone positions must keep1m above the ground.

40 3.2 Measurement of sound insulation The indoor SPL spectrum graph The outdoor SPL spectrum graph

41 1 Abstract 2 3 4

42 4 Summary

43 Speaker placement outside the audiometric room 2 fixed speakers Speaker-speaker 3m Speakers-room boundary 2m Speakersmicrophones>2m GB/T GB/T =1 moved speaker Speaker-speaker 3m Speakers-room boundary 2m Speakersmicrophones 2m 2 fixed speakers Speaker -speaker 1.4m Speakers-room boundary 0.5m Different speakers position should not be in the same place. =1 moved speaker Speaker -speaker 0.7m Speakers-room boundary 0.5m Different speakers position should not be in the same place. Microphone placement outside the audiometric room Microphone placement inside the audiometric room 6 fixed microphones Microphones-room boundary 1m Microphonemicrophone 1.7m =1 moved microphones Microphones-room boundary 1m Microphonemicrophone 1.7m 3 microphones Microphones on the radius of 0.3m 5 fixed microphones Microphones - microphones 0.7m Microphonesspeakers=1.0m =1 moved microphone Microphonesmicrophones 0.7m Microphones - speakers=1.0m Acoustic field characteristics inside the audiometric room Only for internal free field For the quasi free field and the diffusion field

44 Note: Recalibration interval Recalibration interval

45 THANKS