Design of a Simple Audiometer for Hearing Screening at Schools in Rural Bauchi State

Childhood hearing impairment is a significant but under-detected disability in rural communities of Bauchi State, where audiological screening resources are essentially absent from the primary and secondary school health system. This study designs a simple, portable audiometer for hearing screening at schools in rural Bauchi State. The device generates pure tone signals at frequencies of 500, 1000, 2000, and 4000 Hz, covering the critical speech frequency range, using a DDS AD9833 signal generator module controlled by an Arduino Nano microcontroller. Output amplitude is regulated through a digitally controlled potentiometer (MCP41010) to deliver calibrated hearing level intensities from 20 to 80 dB HL in 10 dB steps. Signal delivery is through audiometric headphones (TDH-39 equivalent) with matched acoustic impedance to maintain calibration accuracy. A simple response button pressed by the child subject triggers LED indication at the testing console. The user interface provides a simplified test sequence guidance display suitable for use by non-audiologist school health officers after brief training. Device calibration was performed against a calibrated sound level meter in an anechoic box to verify frequency accuracy and output level accuracy. Frequency accuracy was within plus or minus 2 Hz of target frequencies and output level accuracy was within plus or minus 3 dB HL, meeting ISO 8253-1 audiometer specification class II requirements. Feasibility testing was conducted at a rural primary school in Dass LGA, screening forty pupils and successfully identifying three probable hearing loss cases subsequently confirmed by referral audiometry. Keywords: audiometer, hearing screening, school health, rural community, Bauchi State.