The Audiogram

Drag The Points On the Graph to Test Your Hearing

Put on headphones. Drag the points down until the sounds are only just audible.



What to expect:

This little demo is not too unlike the standard audiometric test known as a pure-tone audiogram. We present pure tones of different frequencies at different sound levels, and adjust their level until they become inaudible in order to measure the "threshold". Obviously, the quieter you can make the sound and still hear it (i.e. the lower your threshold) the better. You can use the buttons beneath the graph to switch from the left to the right ear. You may find it interesting to compare your left and right ears and see if they are equally sensitive. 

Note that, unlike in a clinical audiogram, here we are plotting the sound intensity simply as "dB full scale", meaning decibel below the maximum output that the computer can produce given how powerful your soundcard or amplifier, what volume settings it has, and how sensitive and accurate your headphones are. Obviously, if your computer or headphone amp has its volume turned down then your thresholds may seem lower than they would otherwise be. Similarly, if you are sitting in an environment with background noise, that noise will mask the quietest tones and your threshold will again seem higher than it really is. To do an audiogram as a clinical test, an audiologist would:

  1. put you in a sound proof chamber to minimize background noise, and 
  2. use calibrated headphones, to be able to work out how many dB SPL (sound pressure level) or how many dB HL (hearing level) the dB full scale correspond to. 

Note that, when an audiogram is expressed in dB SPL or dB full scale, then you would expect it to be "U shaped", meaning that your thresholds for sounds between 1000 and 4000 Hz should be the lowest, and thresholds should increase for frequencies which are much lower or much higher than that range. That is because our outer and middle ears have their own resonant and acoustic impedance matching behaviors which make them very good at transmitting 1-4 kHz sounds to the inner ear, but much less good at transmitting higher or lower frequencies. So if we want to make a 100 Hz tone and a 4000 Hz tone that are meant to sound equally loud, then we actually have to make the 100 Hz tone physically more intense. This "iso-loudness curve" shows that effect:

iso loudness curve from wikipedia

In clinical audiograms, expressed in dB HL, the frequency dependent changes in sensitivity of the human auditory system are subtracted out, so a clinical audiogram should be fairly flat, rather than U-shaped, with values near zero. Unless there is something wrong. What healthy and unhealthy clinical audiograms look like you can find out on the next page.