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Exam 1997 Question 4

"A tape recorder is quoted as having a frequency response of 500Hz to 5000Hz within 3dB. Explain what this statement means. Describe the procedure by which the frequency response of this tape recorder might have been measured. Discuss the suitability of this tape recorder for recording speech."

20 things you should mention:

  • Frequency Response
    • y-axis is response
    • response = ratio of output amp to input amp
    • measured in dB
    • shows how source spectrum is modified by processing
    • values within 500-5000 within 3dB
    • worse outside these freqs
    • e.g. picture
  • Procedure
    • record pure tones
    • at frequencies between 20 to 20000 Hz
    • at constant (or measured) input amplitude
    • measure output amp on playback
    • calculate db = 20 log (out/inp)
    • plot response graph
  • Utility
    • not very good for speech
    • significant energy outside 500-5000
    • in particular F1 region
    • could have an effect on intelligibility
    • bass-tinny treble-muffled
    • relate to ideal response
    • e.g. pictures

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