Hearing protection, protection means no danger, no aggression, no accident; so-called protection, is preparedness, preparedness, and preparedness means to be prepared for an attack or to avoid victimization, preparedness means to prevent and protect.
The best measure to protect hearing is to control the source of sound, when the noise can not be reduced to a safe limit, people exposed to noise should be equipped with hearing protection. That is, soft plastic, rubber, sound-insulating and sound-absorbing materials made of a certain shape, covering the auricle or closing the external ear canal, to achieve the effect of sound insulation and sound-absorbing attenuation of sound wave intensity.
Content Introduction
The process of hearing damage is generally silent and progressive. Early hearing loss may not affect communication with others temporarily, so it is difficult to cause people to be alert, but after years of accumulation, people who usually do not pay attention to hearing protection will prematurely cross into the hearing loss population and have a pair of prematurely aging ears. Research also shows that human hearing is very delicate. Once the hair cells on the cochlea that sense sound are damaged, one is one less and irreversible.
Voice Recognition
Sound is produced by the vibration of an object, and the vibrating object is called the sound source. Vibrations travel in elastic media (gases, liquids and solids), in the form of waves, whose fluctuations in a certain frequency range act on the human ear and cause the perception of sound.
The normal human ear can hear frequencies in the range of 20 Hz to 20,000 Hz, below 20 Hz is infrasound and above 20,000 Hz is ultrasound. The frequency range of speech signals that people use in everyday speech is between 300Hz and 2000Hz. [5] The unit reflecting the intensity level of sound is decibel, symbolized as dB.
Noise
Noise is a sound that makes life and work uncomfortable, annoying and unbearable, and is usually an irregular combination of sounds of different frequencies and intensities. If a conversation at a distance of about three steps requires a raised voice to communicate, we are usually considered to have been exposed to a hazardous noise environment.
Industrial noise
The sound generated in the production process, its frequency and intensity is not regular, sounding annoying, known as productive noise or industrial noise. The presence of hearing impairment, harmful to health or other hazards of sound noise sound level ≥ 80dB work for noise operations.
Classification
Industrial noise can be divided into mechanical noise, aerodynamic noise, electromagnetic noise due to the different dynamics and ways of generation.
According to the characteristics of noise changes over time, industrial noise can be divided into steady-state noise, non-stationary noise and impulse noise.
(1) steady-state noise: in the observation time, using the sound level meter "slow gear" dynamic characteristics of the measurement, sound pressure level fluctuations <3dB of noise; such as the textile industry loom, spinning machine open continuous work, the noise in the workshop always remain stable state.
(2) non-stationary noise: in the observation time, using sound level meter "slow gear" dynamic characteristics of the measurement, sound pressure level fluctuations ≥ 3dB of noise; such as machining industry milling machine, drilling machine, lathe, grinding and other operations, the noise is very large when processing parts (may exceed 90dB), no parts of the noise is smaller when processing ( 80dB or so), the noise that workers are exposed to is non-stationary noise.
(3) pulse noise: noise suddenly burst and quickly disappear, duration ≤ 0.5 seconds, interval time > 1 second, sound pressure RMS change ≥ 40dB of noise; such as machining industry punching machine, calcining machine, shear bed, sheet metal and other operations.
Source
(1) mechanical impact, friction and rotation and generated, such as looms, ball mills, chainsaws, forging hammers, stamping, crushing, blasting and other noise generated.
(2) sudden changes in gas pressure caused by the disturbance of airflow and generated, such as blowers, steam whistles, injectors, centrifugal fans, air compressors, boiler exhaust venting and other noise issued by the.
(3) due to magnetic field pulsation, power frequency pulsation caused by the vibration of electrical components, such as generators, transformers, rectifiers, etc. issued by the noise.
At present, the top ten industrial noise sources affecting workers' health and seriously polluting the environment are fans, air compressor motors, diesel engines, looms, punching machines, circular saws, ball mills, high-pressure venting exhaust and rock drills, etc.
Types of noise work
The industries and types of work where noise hazards exist are very widely distributed, and the "Classification Catalogue of Occupational Disease Hazards" issued by the Ministry of Health in 2002 lists 61 industrial types of work that may lead to noise deafness. In the actual work noise mainly comes from.
(1) machining and manufacturing: undercutting, shearing, forging, stamping, rolling, riveting, sand dropping and shaping.
(2) metal surface treatment: polishing, sandblasting, cleaning.
(3) coal mining and other mining: rock drilling, blasting, tunnelling, etc.
(4) textile and apparel: tying, spinning, weaving, strip making, dyeing, etc.
(5) thermoelectric power: coal crushing, ball milling, steam engine power generation, stoker
(6) cement manufacturing: crushing, grinding.
(7) highway, railroad, water conservancy construction: tunneling, blasting.
(8) construction materials: stone crushing, grinding, rock drilling, drilling, piling, etc.
Noise Hazards
Harmful to human body
The hair cells in the cochlea are auditory sensory cells. There are approximately 40,000 hair cells at birth, and they gradually die as a person grows and ages over the course of his or her life. Noise can also cause hair cells to die. Once the hair cells die, they do not regenerate.
Hearing loss can be classified as temporary or permanent. Just like a lawn, occasionally someone walks on it, the downed grass will recover after a while, but if it is repeatedly trampled, the lawn will turn into hard soil, and this phenomenon is very common.
Temporary: If a person stays in a strong noise environment, tinnitus and hearing loss can be caused for a short time, the hearing threshold increases by 10 decibels, and hearing can return to normal after a few minutes from the noise environment, this phenomenon is called hearing fatigue; if it stays longer, the hearing threshold increases by 15 to 30 decibels, and hearing takes hours or even days to recover, this is usually called temporary hearing loss.
Permanent: Irrecoverable hearing changes caused by being in a noisy environment are called permanent hearing loss. The most obvious impact of permanent hearing loss on a person's life is that it impedes verbal communication. If the hearing loss becomes further severe, it can lead to complete deafness.
The effects of noise on the human body are manifold.
(1) Auditory system damage: It was noticed early on that long-term exposure to noise of a certain intensity can be harmful to the auditory system, mainly in the form of.
-- decreased auditory sensitivity, poor language reception and signal discrimination.
-- Tinnitus, hearing abnormal sounds out of thin air.
-- difficulty in conversation, always having trouble hearing what people are saying
--distorted hearing of all sounds.
--severe hearing loss and occupational occupational noise deafness can result.
(2) Multi-system and organ damage: After long-term research, it has been found that noise can also affect the normal physiological functions of other systems.
-- neurological system with neurasthenia syndrome, EEG abnormalities, and dysfunction of the vegetative nervous system.
--Cardiovascular system with unstable blood pressure (mostly increased), accelerated heart rate, changes in ECG (sinus arrhythmia, ischemic type changes)
--digestive system with reduced gastric juice distribution, slowed peristalsis, decreased appetite.
--endocrine system manifests hyperthyroidism, increased adrenocortical function, sexual dysfunction, menstrual disorders, etc.
Occupational noise deafness and its symptoms
Occupational noise deafness occurs when the hearing nerve cells are damaged by working in a noisy environment for a long time without proper recovery. This is a condition in which both ears are damaged. When examined with an audiometer, the loss of hearing in the high-frequency part of the ear centered at 4,000 Hz is the first thing that occurs, and then gradually expands until speech is not heard.
The main manifestations of occupational noise deafness are tinnitus, deafness, headache, dizziness, and in some cases, insomnia and a feeling of head swelling. The early manifestation is tinnitus within a few hours after work, and later it is persistent and the symptoms no longer disappear. Some patients also suffer from vertigo, nausea or vomiting.
Blast deafness and main symptoms
Some operations such as blasting, weapons testing, etc., due to improper protection or lack of necessary protective measures, can cause serious damage to the auditory system and loss of hearing due to the strong noise and shock waves generated by the explosion, called blast deafness.
Rupture of the tympanic membrane, misalignment of the middle ear auditory bone, tearing of the ligaments, breakage of the inner ear spiral apparatus, and even concussion occur. Patients complain of tinnitus, ear pain, nausea, vomiting, and vertigo. Examination may reveal severe hearing impairment or even total deafness. If the inner ear is not severely damaged, hearing may be fully or partially restored.
Hazardous factors
Long-term exposure to noise can be harmful to humans, and the degree of harm depends mainly on.
(1) the size of the noise intensity (sound pressure): the greater the intensity, the greater the hazard.
(2) the frequency of high and low: the lower the frequency, the greater the harm.
(3) the length of contact time: the longer the contact time, the greater the hazard.
(4) the characteristics of the noise: impulse noise is more harmful than steady state noise.
(5) The way of contact: continuous contact is more harmful than intermittent contact.
(6) individual sensitivity: individual sensitivity also has some influence, which is expressed in: in the same noise environment, some people have serious hearing loss, some people are lighter.
Processes of impact
The process of noise effects on hearing loss
(1) Initially, the hearing loss is in the high frequency band (1,000-6,000 Hz, especially at 4,000 Hz with a "V" sag), and the speech band is not affected and does not yet prevent daily conversations and conversations.
(2) In case of continuous exposure to high noise, the condition will further develop and the hearing loss in the speech frequency band will start to reach a certain level, i.e., it will affect the ability to hear conversations.
(3) When the phenomenon of deafness appears, irreversible pathological changes have occurred.
Preventive measures
The main measures to prevent hearing loss are engineering control measures, management measures and individual protective measures (i.e., the use of ear protectors, also known as hearing protection).
(1) engineering control measures should be the first consideration to improve the process of noise generation, equipment and materials, starting from the treatment of noise sources, as far as possible to fundamentally reduce the generation of noise, in addition to some other such as sound insulation (to add a cover to the noise equipment), vibration isolation (under the noise generating equipment with spring dampers, rubber, cork, asphalt felt, glass fiber felt, etc.), sound absorption (in the metal plate coated with a layer of damping materials, such as asphalt, soft rubber or other polymer coatings) control measures, but also can play a noise reduction effect.
(2) Management measures are very important measures As long as there is a noise hazard, management measures are necessary, and management includes.
-- Routine monitoring and recording of noise exposure.
--Record management of hearing tests for workers.
--evaluation of engineering control measures.
-- management and maintenance of noise reduction equipment.
--establishment of protocols for the selection, use and maintenance of ear protectors, and supervision and inspection
-- management of noise-polluted areas, including the posting of warning signs requiring all persons entering the area to wear ear protection; or limiting and reducing the number of persons entering and the duration of their stay
--a review of the implementation of the hearing protection program
-- Rational arrangement of labor and rest to shorten the exposure time.
(3) If the noise intensity in the workplace cannot be effectively controlled temporarily, wearing personal protective equipment is an effective measure to protect workers' hearing organs. Various designs of ear protectors can be used by different operators, and if they are properly selected, used and maintained, they can achieve good noise reduction effects.
Management requirements
National health standards have been set for noise in the workplace. If the noise in the workplace is lower than the national standard, for the majority of workers who work 8 hours a day or 40 hours a week, the possibility of occupational hearing damage is small; if the noise in the workplace is higher than the national standard, the employer should take comprehensive measures to reduce the noise intensity in the workplace, and according to the national standard [Guide for the selection of hearing protectors (GB/ T23466-2009)] for workers with ear plugs, earmuffs.
Workers can find out whether the noise meets the requirements of national standards through the workplace noise monitoring results notification board.
(1) Enterprises should develop their own hearing protection plans for workers and designate specially trained personnel to organize and implement them.
(2) The enterprise shall monitor the noise in the workplace, identify the group of people whose noise exposure is greater than or equal to 85 dB, and inform the workers concerned of the monitoring results.
(3) Workers exposed to noise operations should be subject to basic audiometry and regular follow-up audiometry.
(4) Enterprises should equip personnel exposed to noise operations with ear protectors that have sufficient noise attenuation capacity and are comfortable to wear.
(5) Regular training on hearing protection, inspection of engineering control measures and the use of ear protectors to ensure the effectiveness of hearing protection.
Protective Products
Product categories
Personal protective equipment used to prevent noise hazards are commonly available in two categories: earplugs and earmuffs.
(1) Earplugs are materials with sound insulation that can be inserted into the external ear canal. According to the performance is divided into: foam type and preformed two types.
--Foam earplugs use foam type material, which is slow to rebound after being flattened, allowing enough time to insert the kneaded tiny earplugs into the ear canal, which slowly expands to seal the outer ear canal for sound insulation purposes.
-- Pre-formed earplugs are made of synthetic type materials (such as rubber, silicone, polyester, etc.), which are pre-molded into certain shapes and can be inserted directly into the ear canal.
(2) Ear muffs are shaped like headphones, with a sound-isolating cover to cover the outer ear, and the ear muffs are fixed to the head with a headband or neckband with appropriate clamping force between the ear muffs, which can also have slots for use with safety helmets.
Selection Factors
When selecting hearing protection, consider the operating conditions and the special needs of the user.
(1) To have suitable noise reduction.
(2) To meet the requirements of the site environment, such as a hot and humid environment to choose ear plugs if possible.
(3) Not to interfere with the use of other protective equipment, such as the use of safety glasses at the same time as far as possible to choose ear plugs.
(4) Comfort should be relatively high, the user is willing to wear, to ensure sufficient wearing time.
Features of supplies
(1) Earplugs
-- small size, easy to carry, also easy to lose (can be solved by choosing earplugs with wires)
--without interfering with the wearing of other protective equipment.
--comfortable to wear for long periods of time in hot and humid environments than ear muffs
-- Wearing ear plugs requires certain skills, the use of personnel need to be trained.
--Foam earplugs need to be rubbed by hand, not suitable for people who usually have dirty hands.
(2) Ear muffs
--simpler to wear than earplugs and more stable in the wearing position.
-- large size, may conflict with other protective equipment (helmet, glasses, respirator, etc.)
--outdoor, cold operating personnel use can play a warm effect at the same time.
-- Longer service life, usually requires maintenance.
Wearing instructions
(1) Before entering the noise workplace
--check whether the earplugs and earmuffs are intact
-- Wear them according to the correct wearing method.
--Do a fit check.
(2) In noisy work areas
-- Always insist on wearing them correctly
(3) Leave the workplace
-- Remove earplugs and earmuffs when you reach a safe area
(3) When leaving the workplace --- follow the product instructions and wash the reusable earplugs and earmuffs properly.
Wearing method
Users should read the product instruction manual carefully before using earplugs and earmuffs and wear them correctly according to the product instruction.
(1) Ear plugs
-- Wash your hands before wearing foam ear plugs.
--when wearing ear plugs in the left ear, flatten and knead the ear plugs fine with the left hand while pulling the left ear auricle upward and outward from the back of the head with the right hand to straighten the ear canal as much as possible, while using the left hand to insert the ear plugs into the ear canal, which expands and then takes shape in the ear canal to block the ear canal.
-- Wearing the right ear plug in the same way.
Wearing pre-formed ear plugs must also be done by pulling the ear canal apart with the hand and inserting the ear plugs directly into the ear canal without rubbing before inserting them.
(2) Ear muffs
Different earmuffs have slightly different ways of wearing and adjusting, so you should read the product manual in detail. It should be noted that you should try to adjust the position of the earmuff cups on the headband and neckband so that the two ears are located in the center of the cups and completely cover the auricle; the headband should be placed vertically on the top of the head; in addition, hair, beard and earrings may affect the sealing of the earmuffs, so try to move the hair to a suitable position, and if the earrings affect the sealing, you should take off the earrings to ensure the sealing of the earmuff gasket.
Air tightness inspection
After wearing ear plugs, you should do an airtightness check of ear plugs: enter the noisy working environment, cover both ears with the palms of both hands, listen to the sound outside, and then remove both hands, if there is no obvious difference between the sound heard before and after, it means that the fit is good. If the sound difference is large, it means that the earplugs are not well fitted with the ear canal and need to be worn again.
Maintenance and replacement
The service life of earplugs and earmuffs is limited and they need to be replaced and maintained. The maintenance, care and replacement requirements vary from product to product, users should read the product instruction manual carefully and maintain and replace them correctly as required:.
(1) Earplugs
--ear plugs that cannot be washed, dirty and broken should be discarded and replaced with new ones.
--ear plugs that can be washed and reused should be replaced when they are damaged or deformed.
--After cleaning, earplugs should be placed in a ventilated place to dry naturally and should not be exposed to the sun.
(2) Ear muffs
--Earmuff gaskets can be wiped clean with a cloth dipped in soapy water, but the entire earmuff should not be immersed in water and should not be exposed to chemicals as much as possible.
--ear muff gaskets will age or break after long-term use and should be replaced with accessories in due course according to the manufacturer's recommendations
--ear muff headband will not fit well when it becomes loose and needs to be replaced with new ear muffs.
--Storage in a clean and dry environment, avoid direct sunlight.
Attention
Removing ear plugs
To remove the earplug, rotate the earplug by hand and slowly turn the earplug out of the ear canal; do not yank the earplug out of the ear canal quickly and directly.
Noisy places
Always insist on wearing ear plugs and earmuffs in noisy places. The damage to hearing caused by noise is related to the exposure time and exposure intensity, and insufficient wearing time is often an important reason for the failure of protection. If a workplace operator needs to wear ear plugs and earmuffs for 8 hours, the nominal noise reduction value of the ear plugs and earmuffs used is 30dB.
-- Wearing for 8 hours (100% of the time), able to achieve 30dB of noise reduction effect.
--Worn for 7.5 hours (93.7% of the time) effective protection of only 12dB (40% protection effect)
--wear 4 hours (50% time), effective protection 3dB (10% effective protection)
It can be seen that the effective protection will be sharply reduced when wearing time is shortened. Although there will be some discomfort and discomfort after wearing ear plugs and earmuffs, and feeling that speech communication is affected, hearing loss is a gradual process, and in order to protect your hearing as well as your own and your family's future, you should always wear ear plugs and earmuffs correctly in noisy workplaces.
Communication
What if I need to communicate in a noisy workplace?
The purpose of ear protectors is to reduce the noise level. After wearing ear protectors, the user can still hear a certain intensity of sound, just like wearing sunglasses and still seeing the surroundings.
(1) When communication is needed for a short period of time in a noisy workplace, get as close to the worker as possible and raise your voice and speak loudly as conditions permit; or use paper and pencil to write and communicate.
(2) You can use one press to hear earmuffs, such earmuffs restore or amplify the external sound to the rated sound pressure level through the servo circuit function, so that the wearer can hear the sound of the external environment more clearly when the circuit is opened.
(3) Using noise-canceling communication products, such ear protectors can be connected to radio intercoms, digital cordless phones or cell phones to improve the clarity, accuracy and convenience of communication while reducing noise. There are good applications in military, petrochemical, airport, construction, rescue, etc.
Occupational Medical Examination
Occupational health checkups during employment are regular examinations of the health status of workers engaged in long-term noise work by the employer in accordance with national regulations. 2007 national promulgation of the "Technical Specification for Occupational Health Supervision" for workers exposed to noise work have detailed provisions for the periodicity of medical examinations, once a year.
The purpose of occupational health checkups during the on-the-job period is to detect patients with hearing loss disease at an early stage, to detect workers with occupational contraindications in a timely manner, and to conduct dynamic observation of "observation subjects" so that those found to have occupational contraindications or early occupational health impairment can be transferred and arranged for appropriate work in a timely manner. In addition, through the occupational health examination during the work period, it is also possible to dynamically observe the health changes of the worker group and evaluate the effect of noise hazard control in the workplace.
Regular occupational health checkups should focus on asking whether there is fluid in the external ear canal, ear pain, tinnitus, deafness, vertigo and other ear symptoms and noise exposure history, and focus on checking pure tone hearing threshold test and electrocardiogram.
