Is there an inevitable connection between deafness and dumbness? How can we protect our ears scientifically?

The importance of hearing is self-evident. This year, the stories of two girls made us realize once again the importance of hearing protection.

One is Jiang Mengnan, "Person Who Moved China 2021". With her strong willpower, she broke out of the silent world, regained her "voice" by installing a cochlear implant, and was admitted to Tsinghua University to pursue a doctorate. The other is Ruby in the 94th Academy Award Best Picture "Hearing Girl". As the only hearing member of a deaf-mute family, she faced conflicts between deaf-mute family members, conflicts between family and society, and conflicts between reality and dreams in the process of pursuing her dreams, but she overcame difficulties with a positive and optimistic attitude towards life and understanding and care.

Jiang Mengnan (Source: CCTV News)

Stills from "Hearing Girl" (Source: Douban)

This can't help but make us think: How do we hear sounds? Why does hearing loss occur? What can we do about hearing loss? How can we enter the world of hearing-impaired people and get along with them?

Part 1

How do we hear sounds?

Our auditory system can be divided into three parts: the outer ear, the middle ear, and the inner ear. Sound is transmitted to the eardrum through the outer ear and causes it to vibrate. The vibration is transmitted to the cochlea of ​​the inner ear through the three ossicles in the middle ear, causing the fluid in the cochlea to move. The movement of the fluid is converted into electrical stimulation by the hair cells, and finally transmitted to the brain through the auditory nerve and perceived as sound.

Auditory system structure (Source: World Hearing Report)

Part 2

Why does hearing loss occur?

Everyone has a baseline hearing ability at birth. Later in life, hearing can be affected by many factors. Negative factors such as ear diseases, high-intensity noise, and aging can cause hearing loss, while positive factors such as good ear hygiene, immunization, and staying away from noise can prevent hearing loss.

Factors affecting hearing (Source: World Hearing Report)

Part 3

What is the relationship between "deafness", "hard of hearing" and "hearing loss"?

The hearing threshold of a normal person's ears is 20 decibels or better. When a person's hearing threshold is greater than 20 decibels, they are considered to have hearing loss. The 2021 World Hearing Report divides hearing loss into seven levels: mild, moderate, moderately severe, severe, profound, total deafness and unilateral deafness. Patients with different degrees of hearing loss have worse hearing experience in quiet and noisy environments.

In our daily life, "hard of hearing" refers to mild to severe hearing loss. If there is such a symptom, it should be taken seriously and relevant measures should be taken in time. "Deafness" refers to profound hearing loss, which means that the person can hardly hear any sound or cannot hear anything at all.

Hearing loss can be divided into three types according to the location of the lesion: hearing loss caused by lesions in the outer ear or middle ear that prevents sound from being transmitted to the inner ear is called conductive hearing loss; the inability to perceive sound and cognitive dysfunction caused by lesions in the cochlea/auditory nerve is called sensorineural hearing loss; hearing loss caused by the simultaneous presence of the above two factors is called mixed hearing loss.

Part 4

Is there a necessary connection between deafness and dumbness?

In life, there is a saying that "nine out of ten deaf people are dumb". In fact, there is no necessary connection between deafness and dumbness. Deafness is a disorder of the auditory system, while dumbness is a disorder of the vocal organs. However, patients with congenital deafness cannot hear speech from the very beginning, and lose the opportunity to imitate and learn language. Even if some patients with acquired deafness initially learn some basic languages, they may lose their language ability again due to deafness.

Part.5

How do cochlear implants help people regain their voice?

Jiang Mengnan was able to hear again by installing a cochlear implant. What is the principle? In fact, a cochlear implant can be divided into two parts: the external system and the implant system. The external system includes a microphone, a speech processor, and an external transmitter. First, the microphone can sense the sound, then the speech processor converts the sound signal into an electrical signal, and finally the external transmitter is used to transmit the electrical signal to the implant system. After the internal receiver of the implant system receives the electrical signal, it transmits it to the electrode array to directly stimulate the auditory nerve.

Source: World Hearing Report

There are two points we need to pay attention to about cochlear implants. First, cochlear implants bypass damaged cochlear hair cells and directly stimulate the auditory nerve to produce hearing, making them a reasonable treatment for patients with severe or profound sensorineural hearing loss. However, cochlear implants are ineffective for hearing-impaired people with damaged auditory nerves. Second, there is a difference between the sounds heard by hearing-impaired people with cochlear implants and normal people. After the implant surgery is completed, rehabilitation training is still required to maximize the benefits of the cochlear implant.

Part 6

How to protect our hearing?

1. Prevention. In daily life, effective measures to prevent hearing loss include immunization, careful use of medication under the guidance of a doctor, maintaining ear hygiene, minimizing the time spent in noisy environments, and using electronic devices properly.

2. Early detection. Key groups such as adolescents, workers in noisy environments, and the elderly can use hearWHO and hospital hearing tests to regularly screen their hearing to ensure that hearing loss is detected at the earliest possible stage.

3. Early intervention. Once hearing loss is detected, early intervention should be carried out. Current medical treatments can cure most ear diseases and may even reverse the related hearing loss. Even in cases where hearing loss is irreversible, the use of hearing technologies such as hearing aids and cochlear implants, learning alternative communication methods such as sign language and lip reading, and other rehabilitation treatments can improve the patient's quality of life and realize their potential.

Finally, please respect, understand and care for the hearing-impaired people around you. I hope that with the progress of society and technology, we can soon realize the world described in the World Hearing Report: in this world, no one will suffer from preventable hearing loss, and those with hearing loss can realize their full potential through rehabilitation, education and empowerment.

Produced by: China Science Expo

Author: Shi Zhiqi

Author unit: Ultrasonics Laboratory, Institute of Acoustics, Chinese Academy of Sciences

The article only represents the author's views and does not represent the position of China Science Expo

This article was first published in China Science Expo (kepubolan)

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