Exam

Audiogram

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Audiogram, Audiometry, Pure-Tone Audiometry

  • Indications
  1. Hearing Loss Evaluation
  • Preparation
  1. Testing environment should be quiet
  2. Patient should avoid loud noise exposure for 14 hours prior to testing (e.g. music via headphones, motorcycle)
  • Technique
  • Pure-Tone Audiometry
  1. Threshold Search Audiometry (Hughson-Westlake Method)
    1. Start with the better hearing ear
    2. Hearing is tested in each ear at frequencies between 250 Hz to 8000 Hz
      1. Frequencies tested at one octave intervals: 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, 8000 Hz
      2. Typical sequence: 1k, 2k, 3k, 4k, 8k, 1k, 500, 250
    3. Each frequency is tested at volumes between 0-90 decibels (logarithmic, loudness doubles every 10 decibels)
      1. Start with an easily heard DB level
      2. Test each heard tone again at 10 DB lower until no response
      3. Then increase by 5 DB, testing until tone heard again
  2. Screening (typical handheld device)
    1. Hearing frequencies tested: 500 to 4000 Hz (speech spectrum)
    2. Loudness tested: 25-30 DB in adults (15-20 DB in children)
  • Interpretation
  1. Normal hearing
    1. All frequencies are heard at 20 decibels or less
  2. Hearing Loss across all frequencies (typically 40 DB loss)
    1. Conductive Hearing Loss (e.g. Cerumen Impaction)
    2. Otosclerosis
  3. Low frequency Hearing Loss
    1. Meniere's Disease (severe)
  4. Low to mid-frequency Hearing Loss (with bone conduction better than air conduction)
    1. Tympanic Membrane Perforation
  5. High frequency Hearing Loss
    1. Noise-Induced Sensorineural Hearing Loss (4000 Hz and higher)
    2. Age-Related Hearing Loss - Presbycusis (2000 Hz and higher)
  • Resources
  1. Audiogram of normal sounds
    1. http://www.nmit.edu.au/Content/images/centre_of_excellence/frequency_intensity_of_sounds.jpg