2007 Sensory Physiology


  • vibrations produce sound waves in the air, which consist of regions of compression and rarefaction, therefore sound is a form of MECHANICAL energy
  • in their simplest form, sound waves consist of a single wavelength (FREQUENCY - perceived as pitch) of a specific amplitude (INTENSITY - perceived as loudness)
    • the human cochlea can detect sounds between 100 Hz and 20 kHz
    • sound intensity is measured in DECIBELS, which is calculated as:
    • dB formula

    • a common reference pressure is 20 µPa, which is the quietest sound detectable by the human ear
      (= 0 dB SPL)
    • human pain threshold is a sound pressure approximately 1-10 million times louder
      (= 120-130 dB SPL)
Sound wave
  • more complex sounds can be decomposed into individual frequency components, each of a specific amplitude
  • mathematically, this process is called FOURIER ANALYSIS, and the cochlea physically performs this type of analysis (see the discussion of the place principle)
Fourier analysis


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