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Questions and Answers
What instrument is commonly hand-held and designed to measure sound levels in a standardized way?
Which component of the Sound Level Meter (SLM) is used for checking the calibration of audiometers?
What is the purpose of the display function in the Sound Level Meter (SLM)?
Which method involves testing the hearing of normal hearing persons, averaging the results, and ensuring the average hearing is at zero on the dial for each frequency?
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What is the most commonly used calibration procedure for earphones today?
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Which instrument is used in calibration to measure sound levels similar to how the human ear responds?
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What is used to fulfill the requirements of IEC 60318-1 for electro-acoustical measurements on insert earphones and headphones?
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Why was the 6-cc coupler originally chosen for supra-aural earphones in electro-acoustical measurements?
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Which standard specifies the Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms?
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What is used to check the ambient level in the test room during audiometric evaluations?
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What should be done with mobile phones, pagers, radios, and other communication devices during audiometric evaluations in the test room?
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What does hearing aid calibration involve?
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Study Notes
Electro-Acoustical Measurements
- Enable electro-acoustical measurements on insert earphones and headphones using:
- A condenser microphone
- A 6-cc coupler (for supra-aural earphones) or 2-cc coupler (for insert earphones)
Artificial Ear (Coupler) Methods
- Fulfill the requirements of IEC 60318-1
- Acoustical impedance similar to that of the human ear
- Originally chosen because the enclosed volume is approximately the same as the volume under a supra-aural earphone/insert earphone for a human ear
Environment Test
- Test environment shall meet the specifications detailed in ANSI S3.1-1999
- Confirmation of an acceptable test environment shall be documented at least annually
- Use of sound-isolated rooms or booths is standard practice
- Test room and audiologist work area should provide proper control of temperature, air exchange, and humidity
- Sound-isolated areas must be provided with warning systems connected to the building warning system
Hearing Aids Calibration
- Calibration includes hearing aid fitting
- Calibrating the hearing aid involves testing the device and making minor adjustments to tailor it to specific hearing needs
- Basic instruments for calibration of an audiometer include:
- Sound level meter (SLM)
- Multimeter
- Frequency counter
- Oscilloscope
- Digital spectrum analyzer
Sound Level Meter (SLM)
- An instrument that measures sound levels in a standardized way
- Responds to sound in approximately the same way as the human ear
- Gives objective, reproducible measurements of sound pressure levels
- Components include:
- Microphones (condenser microphone used for checking the calibration of audiometers)
- Amplifiers (gain changed when SPL range is changed)
- Time-weighting circuits (fast, slow, and possibly impulse and peak time weightings)
- Various filter settings (dBA, dBC, octave and/or third-octave band filters)
- Display function (VU meter, LED indicator, and/or digital readout)
Earphone Level Calibration
- Two basic approaches:
- Real Ear Method: tested the hearing of a group of normal hearing persons, averaged the results, and checked to see that the average hearing of this group was at zero on the dial for each frequency
- Artificial Ear (Coupler) Methods: the most commonly used procedure today
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Description
Learn about the basic instruments used for calibrating an audiometer, including a sound level meter, multimeter, frequency counter, oscilloscope, and digital spectrum analyzer. Understand the functionality of each instrument and how they contribute to precise measurements in sound level calibration.
