How to Calibrate a Audiometer

Audiometers work by playing tones at specific frequencies that represent different parts of the human auditory spectrum. While the complete audio spectrum ranges from 20 hertz to 20,000 hertz, human voices and the notes produced by musical instruments range in frequency from around 30 hertz to around 8,000 hertz. An audiometer score of 0 decibels represents normal hearing, while a score of 100 decibels represents near complete deafness. Because of the complexity of the audiometer and the importance of receiving accurate hearing test results, only a trained audiologist should use an audiometer to test hearing.

Things You'll Need

• Sound level meter
• TDH-49 earphones
• TDH-39 earphones

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Instructions

• 1

  Calibrate the audiometer, using the sound pressure output check. Place the audiometer's earphone on the coupler, then place the coupler over the sound level meter's microphone. Set the audiometer's hearing threshold level to 70 decibels. Measure and record the sound pressure level at each frequency from 500 hertz to 6,000 hertz. Compare the results to the "sound level meter readings" provided in the Reference Threshold Levels. A separate chart is provided for both TDH-39 and TDH-49 earphones.

• 2

  Confirm the calibration of the audiometer by performing a linearity check. Set the audiometer frequency to 1,000 hertz and the hearing threshold level to 70 decibels. Observe the sound level meter while reducing the hearing threshold from 70 decibels to 10, in 10-decibel increments. Each 10 decibel decrease in the hearing threshold level should result in a 10 decibel decrease in the sound level reading.

• 3

  Send the audiometer off for professional calibration if the sound levels deviate from those provided in the Reference Threshold Levels by 3 decibels at any frequency between 500 or 3,000 hertz, 4 decibels at 4,000 hertz or 5 decibels at 6,000 hertz.