Hearing loss is caused by noise, such as decreased hearing sensitivity, increased hearing threshold, hearing impairment and even hearing loss. Can be divided into temporary and permanent.
① Temporary hearing loss
Tinnitus and hearing loss caused in a short time in a strong noise environment will increase the hearing threshold by 65,438+00 dB, and hearing will recover within a few minutes after noise, which is called auditory adaptation. If the noise acts for a long time, the hearing threshold will increase by 15 ~ 30dB, and it will take several hours or even days for hearing to recover. This condition is called hearing fatigue or noise-induced temporary hearing threshold shift (NITTS or TTS), commonly known as temporary hearing loss.
② Permanent hearing loss
Irrecoverable hearing loss caused by noise is called noise-induced permanent threshold shift (NIPTS or PTS), also known as permanent hearing loss. PTS caused by industrial noise is mostly developed from TTS, which has a slow development process. V-shaped or U-shaped hearing loss is formed at 3000~6000Hz on the audiogram, which is called 4000Hz listening trough (dip). High-frequency "listening to the valley" is a typical feature of hearing loss caused by occupational noise, and it is also an early signal of noise deafness. PTS usually develops symmetrically, often accompanied by tinnitus, which sometimes reduces the hearing of high-frequency sounds, but has no obvious effect on language conversation. If it continues to develop, the auditory valley will deepen and expand to high and low frequencies until noise deafness and hearing loss occur.
Hearing loss hearing loss is the manifestation of hearing dysfunction, ranging from weighing hearing or hearing loss to deafness or total deafness. Hearing loss is generally divided into three categories: conductivity, sensorineural and mixed.
Conductive hearing loss: the lesion is in the outer ear or middle ear, which prevents sound waves from entering the inner ear.
Sensorineural hearing loss: the lesion is located in the cochlea, auditory nerve or auditory pathway, which causes hearing loss due to acoustic and cognitive dysfunction.
Mixed hearing loss: any factor leading to conductive hearing loss and sensorineural hearing loss can cause mixed hearing loss, which has the characteristics of both conductive hearing loss and sensorineural hearing loss.
The average pure tone hearing threshold PTA: 500 Hz, 1000Hz and 2000Hz account for 70% of the importance of language intelligibility, which is the key range to measure hearing function. For this reason, the World Health Organization (WHO) adopts the average values of hearing loss at 500 Hz, 1000 Hz and 2000 Hz as the basis for the classification of hearing loss.
In addition to the above-mentioned commonly used classification methods of hearing loss, the World Health Organization (WHO) issued a new classification standard in 1997, which raised the hearing threshold by 4000Hz compared with the previous standard, fully considered the situation of high-frequency hearing loss of hearing-impaired people, and had certain clinical value. Now adopt this new standard. According to the average hearing loss at 500 Hz, 1000 Hz, 2000 Hz and 4000Hz, the hearing loss is divided into five grades: 26~40dB is mild, 4 1~55dB is moderate, 56~70dB is moderate, 7 1~90dB is severe, and 90.