Conventional vs Digital Hearing Aids: Key Differences

This page compares conventional hearing aids and digital hearing aids, outlining the differences between them and explaining the block diagrams of each.

Introduction

Hearing problems often arise from hearing loss due to aging or long-term exposure to sound. This is mainly due to a decrease in sensitivity or the ability to discriminate speech sounds, or both. As people age, their ears become less sensitive to sound and less effective as speech processors. By the time individuals realize this, many of their sensory cells in the inner ear may be damaged or missing. Therefore, they often rely on hearing aids of various types to compensate for this loss.

There are two primary types of hearing aids: conventional and digital. These are distinguished by their functions and internal modules.

Conventional Hearing Aid

Image alt: Conventional Hearing Aid

This type of hearing aid operates on battery power. It’s packaged in a miniature housing to fit easily inside or behind the ear. Figure 1 illustrates a conventional hearing aid. As shown, it includes a microphone, Automatic Gain Control (AGC), filters, a mixer, registers, an audiometer, and a receiver.

The microphone converts sound energy into electrical energy, which is pre-amplified by the AGC module. Filters help remove unwanted frequencies and pass desired ones. The receiver then converts the electrical energy back into sound energy, allowing the person to hear without issues.

Digital Hearing Aid

Image alt: Digital Hearing Aid

Figure 2 depicts a digital hearing aid. It comprises a microphone, Analog-to-Digital Converter (ADC), Digital Signal Processor (DSP), Digital-to-Analog Converter (DAC), receiver, memory, and an audiometer/programmer.

The microphone converts sound energy into electrical energy. These analog electrical signals are then converted into digital signals using the ADC. The DSP chip processes the digital signals and converts them back to analog signals using the DAC. Finally, the receiver converts the analog electrical signals into sound waves for the patient to hear.

Key Differences

The major difference between conventional and digital hearing aids is that conventional hearing aids do not use a DSP, while digital ones do. The use of a DSP chip in digital hearing aids necessitates ADC and DAC ICs, which increases the cost and complexity. However, digital hearing aids react much faster compared to conventional hearing aids.