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Exam 1999 Question 7

"Describe what equipment and what method you would use to make the following measurements: a) the measurement of the intensity of a sound using the dBSPL scale; and b) the measurement of hearing impairment for pure tones using the dBHL scale: and c) the measurement of the perceived loudness of a pure tone using the phon scale."

20 things you should mention:

  • Intensity
    • microphone
    • voltmeter
    • calibrated sounds
    • make voltage ratio to calibrated sounds
    • express in dB re calibrated sound -> dBSPL
    • dBSPL formula, re: 20microPa
  • dBHL
    • sinewave generator
    • attenuator
    • headphones
    • means of calibration to known dBSPL
    • pure tone audiometric procedure to find threshold
    • compare to thresholds of adult normals at that frequency
    • dBHL = individual threshold (dBSPL) - average threshold (dBSPL)
  • Loudness
    • sinewave generators
    • attenuator
    • headphones
    • play two tones, one fixed at test frequency and level
    • one at 1kHz variable in amplitude
    • get subject to match for loudness
    • phon = dbSPL of 1kHz match tone - dBSPL of threshold at 1kHz

© 2000 Mark Huckvale University College London