Traditional hearing aids consist of several components: microphone (referred to as a "mic"), amplifier, receiver (earphone), battery, various volume and tone control knobs, and other electroacoustic devices.
The basic principle of hearing aids involves converting sound signals into electrical signals through a microphone, amplifying and processing the signals through circuits, and then converting them back into sound signals using a receiver.
The microphone, also known as a microphone or transducer, converts sound signals into electrical signals.
After the microphone receives and converts sound signals into electrical signals, they are sent to the signal processing part of the hearing aid for necessary adjustments. This part, also called the amplifier, is the core component of the hearing aid's principle. The main function of the hearing aid is to make sounds audible to those with hearing impairments. Signal processing includes amplification, frequency response adjustment, and input-output curve adjustments, which can be done in analog or digital ways.
The processed and amplified audio signals are sent to the receiver, which is another transducer. Despite the similar appearance to a microphone, the internal structure and principles of the receiver are entirely different. The receiver converts the amplified electrical signals into sound signals or mechanical vibrations, transmitting them into the ear canal.
4. Volume Control
Volume control is a variable resistor or potentiometer used to adjust the current passing through the amplifier. As the resistance of the electric current changes with the volume, adjusting the volume higher requires more current, while lowering the volume reduces the current, making the sound softer.
5. Fine-tuning Components
To meet the needs of different degrees of hearing loss, hearing aids often have fine-tuning components on the amplifier. These components allow precise adjustments to achieve the highest match.
6. Battery Power
Hearing aids rely on batteries to provide the necessary energy. Batteries convert chemical energy into electrical energy. If a battery lacks energy, it will limit the hearing aid's output pressure. Hearing aids require batteries that are small in size, have constant voltage, reliable quality, long lifespan, and are environmentally friendly. Modern hearing aid batteries are zinc-air batteries.
7. Hearing Aid Accessories
Hearing aid accessories may include audio inputs and inductive coils:
Audio Input: Most hearing aids have contact pads or jacks for audio input, mainly used for listening to radios or watching television. Because audio signals come directly from the sound source without undergoing sound-to-electric and electric-to-sound conversion, the quality of input signals is better than those converted through a microphone.
Inductive Coil: An inductive coil is a magnetic induction coil that responds to the electromagnetic field leaked from the handset of a telephone. It amplifies the converted electrical signals, allowing the hearing aid to be used for phone calls. Its advantages include no feedback, no interference, and a high signal-to-noise ratio in noisy environments. A high signal-to-noise ratio means a strong voice signal, making it easy to distinguish.