Exam Question Checklist

Exam 1997 Question 5

"Explain the difference between sound intensities measured in dBSPL and in dBHL. Describe the procedure by which a pure-tone audiogram is measured for a listener. Why is the ear more sensitive to pure tones with frequencies between 1000Hz and 4000Hz?"

20 things you should mention:

• Measures
  • dBSPL is absolute intensity measure
  • re: 20 µPa
  • same reference at all frequencies
  • dBHL is relative measure
  • re: ISO standard values
  • of threshold of audibility
  • of young, normally hearing adults
  • different at different frequencies
• Pure-tone audiogram
  • in quiet room
  • over headphones (typically)
  • present pure tones
  • step in level down to threshold
  • signal from listener
  • 10dB down 5dB up
  • repeat until consistent result
  • convert threshold in SPL to HL
  • HL = SPL - ISO
• Greater sensitivity
  • resonances in external auditory meatus
  • typical frequency response
  • resonance in ossicular chain