How hearing aids work
There are many types of hearing aids, but all electronic hearing aids work the same way. Any hearing aid includes 6 basic structures.
1. A microphone (microphone or microphone) receives sound and converts it into electrical wave form, that is, converts sound energy into electrical energy.
2. Amplifier amplifies electrical signal (transistor amplifying circuit)
3. Headphones (receivers) Convert electrical signals into acoustic signals (ie, convert electrical energy into sound energy).
4. Earmolds (earplugs) are inserted into the external auditory canal.
5. Volume control switch
6. Dry batteries for power supply to amplifiers.
In addition to the above 6 parts, most models of hearing aids also have 3 accessories, or 3 additional circuits (tone control, induction coil, output limit control). A modern electronic hearing aid is an amplifier whose function is to increase the intensity of sound energy and deliver it into the ear as undistorted as possible. Since the sound energy of the sound cannot be directly amplified, it is necessary to convert it into an electrical signal, and then convert it into sound energy after amplification. The input transducer consists of a microphone (microphone or microphone), a magnetic induction coil and other parts. Its function is to convert the input sound energy into electrical energy and transmit it to the amplifier. The amplifier amplifies the input electrical signal, and then transmits it to the output transducer. The output transducer is composed of an earphone or a bone conduction vibrator, and its function is to convert the amplified signal from electrical energy into sound energy or kinetic energy for output. The power supply is an indispensable part for supplying the working energy of the hearing aid. In addition, there is a peak clipping (PC) or automatic gain control (AGC) device to suit the needs of patients with different degrees of deafness.
The working principle of in-the-ear and ear-canal hearing aids
In-the-ear hearing aids can be divided into: in-the-ear (abbreviation) ITE), ear canal type (English abbreviation ITC or CC), mini ear canal type (English abbreviation MITC), invisible deep ear canal type (English abbreviation CIC or TYM). But because they are all worn in the ear, they are also referred to as in-the-ear hearing aids.
Characteristics of in-ear hearing aids: Fits the individual ear; Easy to put on or take off the hearing aid; Make full use of the sound collection function of the outer ear; Comfortable to wear; Less noticeable; Can be used in a normal way Phone: Can also be worn while you sleep; in-ear hearing aids can be customized according to your hearing needs.
In-the-ear hearing aids are probably the most convenient and comfortable type of hearing aids. More importantly: the effect it can achieve on the sound can indeed improve the user’s ability to listen. When we communicate with people, the biggest problem is not that we cannot hear, but that although we hear the voice, we cannot understand the meaning contained in it. We often think that a word contains only one sound. In fact, each word is composed of several different sounds. Now, take the word “three” as an example: the “s” in the SAN sound and the sound of huangu suds deshibao? If you hear the sound of “S”, you know that the word you hear is “three”, Instead of “An”, it can be seen that the high-frequency sound contained in the sound of the word is the key to our understanding of the meaning. 60% of the energy contained in speech is concentrated below 500 Hz (low frequency), that is, on the vowels (such as AN, EN, IA…); 35% of the energy is concentrated between 500 Hz and 1000 Hz (middle frequency); the very little energy left exists on the high-frequency sounds that are closely related to speech. Usually, this characteristic of speech is not a problem for people with normal hearing, but not for people with hearing impairment. When the hearing loss mainly occurs in the high frequency band, because the sound energy contained in the high frequency speech is very weak, the problem is more complicated. No type of hearing aid can restore a damaged hearing system to normal. Hearing aids just amplify the sound to make it easier for you to hear. The difference between the in-the-ear hearing aid and the general hearing aid is that the in-the-ear hearing aid is in a more favorable focus – the ear canal opening, receiving the sound, so it can achieve a more effective sound amplification effect. Our outer ear concentrates low-energy, high-frequency speech near the ear canal to intensify these extremely important sounds. When the hearing aid is worn outside the ear, a long tube is required to connect to the ear, and this tube will resonate. As a result of resonance, the mid-frequency sound is often unnaturally enhanced, and the enhanced mid-frequency sound will easily mask the weak high-frequency sound. In contrast, in-ear hearing aids only use extremely short tubes, so this shielding effect can be effectively reduced. Another advantage of in-ear hearing aids compared to other types of hearing aids is the location of the microphone. Usually the microphone transmits the speech along with the ambient noise to the amplifier. Most of the noise in the environment is dominated by low frequency sounds. If the microphone picks up low-frequency noise and important high-frequency speech at the same time, the louder noise will overshadow the weaker speech. In-ear hearing aids, the position of the microphone is designed on the ear canal where the high-frequency sound is the strongest focus, which can eliminate the disadvantage of high-frequency voice being shielded. In-the-ear hearing aids also have many significant advantages. It is less conspicuous in appearance, and at the same time, the user can engage in various activities without being restricted in movement. The above advantages of in-the-ear hearing aids are closely related to their appearance. The smaller the shape, the more obvious the above advantages. Therefore, invisible deep-ear canal hearing aids are the best, followed by in-the-ear hearing aids and in-the-ear hearing aids.
The basic structure of a hearing aid includes four main parts: microphone, amplifier, earphone, and power supply. The hearing aid converts the sound signal into an electrical signal (electrical energy) and sends it to the amplifier. The amplifier amplifies the weak input electrical signal and then transmits it to the output transducer. The output transducer is composed of earphones or bone vibrators. Its function is to The amplified strong signal is converted from electrical energy to acoustic signal (sound energy) or kinetic energy for output. Therefore, the signal from the earphone or bone vibrator is much stronger than the signal originally received by the microphone, which can compensate the hearing loss of the hearing impaired to varying degrees.
