Design of Low Cost, Easily Operable Pure Tone Digital Audiometer to measure a Person’s Hearing Ability

Abstract

An audiometer is a device that can measure a person’s hearing ability, i.e. if the person’s hearing is normal or impaired in any way (various degrees of deafness). The measurement can then give an indication of what might have caused the impairment (noise, age etc.) Most people have had an ear test done at some point of their life, at school, their workplace, national service or their ENT doctor. The most commonly used scientific method used is to play low level pure tone ‘beeps’ (sine wave) at different frequencies (tone pitch) with varying levels to the test subject, and the person responds by pressing a button if the tone was heard (Bekesy Test).

Audiometers whether standalone or software based are expensive, hence their non-availability in hospitals or homes or training institutions as should be the case. This motivated our team to implement a low cost but effective audiometer referred to as Audiometer 1. This turned out to be very bulky and far from intended the design. A better design using fewer components to generate more frequencies eliminates all these, therefore reduced considerable the size of circuit. The method used the internal timers of the 8051 to generate the required frequencies. A further reduction was attained by removing the power supply module and using a 5v battery required by the microcontroller instead of 5v, -5v, 12v, -12v, 15v and -15v required by different modules earlier. With all these the size of the second design is reduced considerably with attendant reduction of costs.