DESIGN AND CONSTRUCTION OF A LOW-COST HEARING AID

Abstract

A low-cost hearing aid device was designed and constructed to produce an amplified sound for people with hearing loss. A 9V dc was used as the power supply. The condenser microphone was used as input transducer to pick up sound from the environment for conversion to electrical signal, NPN transistor (BC548C) along with three capacitors and five resistors were used as pre-amplifier.to amplify. The integrated circuit (IC) TDA2822M, available in 8-pin mini chip package and specially designed for portable power amplification was used for the amplification function. A 32 ohms ear phone was used as the output transducer to convert the amplified electrical signals back to sound. The computed current gain was 100. Rc was obtained as 3.3Ω, 𝐼𝐵 = 0.025𝐴, 𝐼𝐸 = 2.5𝐴, 𝑅𝐸 = 1.5Ω, the impendence 𝑍0 = 1.9Ω. Index Terms: Design, construction, hearing aid, hearing loss, integrated circuit, low-cost, npn transistor