What is pure tone audiometry?
Pure tone audiometry is a test is to get a qualitative and quantitative analysis of the patients hearing. The frequency range tested is 125 Hz to 8000 Hz.
What are the aims of pure tone audiometry?
- Analysis of the patients hearing loss (conductive hearing loss, sensorineural hearing loss or mixed loss)
- For pre-operative and post operative evaluations
- Medico-legal purposes
- For prescription of hearing aid
- In malingering patients
How is pure tone audiometry done?
Pure tone audiometry is carried out in a sound proof room. Air conduction thresholds for frequencies upto 125, 250, 500, 1000, 2000, 4000 and 8000 Hz, and bone conduction thresholds for 250, 500, 1000, 2000 and 4000 Hz are done. The patient is told to raise his finger or give a signal when he appreciates the slightest sound.
Inference: The intensity of the sound raised above the normal level is directly proportional to the degree of hearing loss. The bone conduction hearing is indicative of the cochlear function.
The difference between the thresholds of air and bone conduction is a measure of the conductive hearing loss. The audiometer is calibrated such that a normal person would have an air bone gap within 20db with bone conduction higher than air conduction. Sensorineural hearing loss shows reduction in threshold of both bone conduction and air conduction.