that amplify the sounds that hearing-impaired people can't hear according to their needs, and then use their residual hearing to send the sounds to the brain's auditory center so they can hear them. The main differences between the various types of hearing aids
are their appearance, size and internal circuit design.
The construction of hearing aids has not changed much since the early 1900s, except that with the advancement of electronic technology, the size of the parts has gradually decreased, the sound quality has improved, and more control options have become available.
Basic structure
Microphone
(
microphone
)
Sound is a kind of vibration wave
We call it sound wave, sound wave is the vibration of the air molecules, and the microphone is the sound wave signal is converted into the relative electric signal, to the expander
Amplifier
(
amplifier
)
The amplifier is the heart of the hearing aid, and its function is to amplify the electrical wave signal.
The receiver
(
receiver
)
is just the opposite of a microphone, taking the increased electrical energy and turning it back into sound waves.
Batteries
(
battery
)
Provide the source of power needed to operate a hearing aid. As with other parts of a hearing aid, batteries in hearing aids have undergone a process of miniaturization, and the most common type of battery nowadays is the zinc-air battery (zinc-air
battery)
. battery)
It is the most widely used battery for hearing aids with the most storage capacity and low pollution.
Volume control
(
volume
controller
)
Generally there is an adjustment knob on the hearing aid to control the volume level of the hearing aid.
Shell
(
shell
)
Different hearing aids have different shells, and in-the-ear hearing aids are usually customized to fit the shape of each patient's ear canal.
Principle of operation
Hearing aids convert sound signals into electrical signals, which are amplified and then converted into acoustic signals to amplify sound. In the process of energy conversion, it is the microphone and the receiver that realize the function of transducer.
I.
Microphone microphone is the input transducer, the acoustic energy into electrical energy.
II.
AmplifierAmplifier amplifies the weak voltage converted by the microphone.
Three,
ReceiverThe receiver is another transducer, just the opposite of the microphone, which converts the amplified electrical signal into an acoustic signal or a mechanical vibration that is transmitted into the ear canal. A receiver that converts to an acoustic signal is an air-conducting receiver, and a receiver that converts to a mechanical vibration is a bone-conducting receiver.
Four.
Volume RegulationVolume regulation is a variable resistor or potentiometer used to regulate the current through the amplifier, and the volume varies with the resistance of the electrical signal. When the volume is turned up, more current is required; when the volume is turned down, the current through the amplifier is reduced, making the sound lighter.
V.
Fine-tuning potentiometers in programmable hearing aids, through the computer programming to carry out a variety of fine-tuning adjustments, so that the adjustment is more fine and accurate, and can be more fine-tuned to compensate for the hearing loss, including:
1. Tone modulation control, to change the frequency response of hearing aids;
2. Peak clipping, which can control the maximum output of the hearing aid;
3. Automatic gain compression modulation, which controls the sound within a comfortable loudness range;
4. Gain modulation (gc): adjusts the hearing aid gain.
6.
Battery Generally speaking, the greater the gain and output of the hearing aid, the greater the battery energy required, and the corresponding battery size is also larger. If a battery does not have enough energy, it will limit the output sound pressure of the hearing aid.
The requirements for batteries in hearing aids are: small size, constant voltage, reliable quality, long life, and environmentally friendly. Today's hearing aid batteries are zinc-air batteries (button cells).
VII.
Accessories for hearing aids can include audio inputs and inductive coils:
1. Audio Inputs: Most hearing aids have contact tabs or jacks for audio inputs, which are mainly used for listening to the radio or watching TV. Because the audio signal comes directly from the sound source without the conversion of sound - electricity and electricity - sound, the quality of the input signal is better than the signal converted by the microphone.
2. Inductance coil: Inductance is a magnetic induction coil that can correspond to the electromagnetic field leaked from the receiver on the telephone, converted to an electrical signal and then amplified so that the hearing aid can be used to listen to the telephone. The advantages are no whistling, no interference, and a high signal-to-noise ratio in a noisy environment. The signal-to-noise ratio is the difference between the speech signal and the environmental noise, and a high signal-to-noise ratio is a strong speech signal that is easy to distinguish.