OSCILLA SM930 Calibration Manual
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OSCILLA SM930 Calibration Manual

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ID: 984 / ver. 204

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Summary of Contents for OSCILLA SM930

  • Page 1 ID: 984 / ver. 204...
  • Page 2 General information: Due to tolerances in electronics and transducers (telephones and bone conductor), it is necessary to calibrate the sound level to the correct intensity. Calibration is done with the transducers that belong to the audiometer. If a transducer is replaced the audiometer has to be calibrated with the new transducer. The device has a built-in table for the ISO hearing level offsets (called RETSPL values).
  • Page 3 Using the calibration mode: When in calibration mode, the tone attenuator keys are used to change the calibration values. Changes are stored at once when done. The ‘AIR’ key select if the left or right telephone is calibrated. The frequency keys select the frequency to calibrate. A calibration value is displayed in the right display, and can be set between 0 and 200, corresponding to -25 dB to +25 dB.
  • Page 4 Adjustment of the trimmers. There is one trimmer in the device, for setting the DC-offset of the output stage. Normally it does not need to be adjusted, so to perform a normal calibration, it is not necessary to disassemble the cabinet. If clicks are heard in the telephones when changing channel between left and right, an adjustment of the trimmer should be done.
  • Page 5 Calibrate tone levels: Place the left telephone on the measuring microphone, and ensure it fits tightly. Set the audiometer and the bandpass filter on the calibration equipment to 125Hz. Adjust to 80dB (plus microphone correction factor) deflection on the calibration equipment. Set the audiometer and the bandpass filter to the next frequency and adjust again to 80dB deflection.
  • Page 6 RETSPL table for TDH39 telephones (ISO-389-1995) 25.5 11.5 1000 1500 2000 3000 4000 6000 15.5 8000 RETSPL table for DD45 telephones These values are store in the audiometer’s memory by default. 47.5 1000 1500 2000 3000 4000 6000 20.5 8000 ID: 984 / ver.
  • Page 7 Changing the hearing level offsets: The hearing level offset values are stored in the audiometer’s memory. They can be changed if desired, for example to use another standard, or if the ISO standard is changed. This is done in a special mode activated by holding down the keys ‘FREQUENCY DOWN’, ‘MASKING ATTENUATOR DOWN’...

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