Audiometry
Noise induced hearing loss (NIHL) occurs when the sound damages the sensitive structures in the inner ear. Sounds can be harmful when too loud and brief or loud and long lasting. NIHL can be immediate or can take time to develop. It can be both temporary and permanent and affect one or both ears. Often you are not aware of the damage until years later when you are unable to hear people speaking especially if there is background noise or on the telephone. It is important to be aware of loud noise as NIHL cannot be cured but it is preventable.
NIHL can be caused by a one-time intense impulse of sound such as an explosion, or by continuous exposure to loud noise over an extended period of time.
Recreational activities can also put you at risk from NIHL - motorsports, shooting, listening to loud music through headphones, playing in a band, and attending loud concerts. Other sources of loud noise in the home can include lawnmowers, power tools and other machinery.
Sound is measured in decibels (dBA). Long repeated exposure to sounds above 85DbA can cause hearing loss. If the sound is very loud the damage done occurs more quickly.
Decibel Ratings
The following sounds listed have the average decibel rating:
Normal conversation - 60-70dBA
Cinema - 74-104dBA
Motorcycles - 80-110dBA
Music through headphones at max volume, concert - 94-110dBA
Sirens - 110-129dBA
Fireworks display - 140-160dBA
The Risks
Sound waves enter the ear via the ear canal and cause the ear drum (tympanic membrane) to move. This movement in turn causes vibrations in the small bones (hammer, anvil, and stirrup) in the middle ear and transmit the sound across to the fluid in the inner ear. The vibrations cause the fluid in the cochlear to ripple. The cochlear is lined with tiny hair cells (sterocilia) that move up and down with the fluid. Movement of the hair cells opens pore-like channels and chemicals then flow to create electrical signals to the auditory nerve. These signals are then conveyed to the brain where they are interpreted into sound.
NIHL is caused by damage to the hair cells which never recover.
Loud noise can also cause tinnitus which is buzzing or ringing in the ears. This condition may be temporary or permanent.
NIHL can be prevented by understanding the hazards and trying to minimise them.
The Assessment
Audiometry is the test to assess your hearing over a wide range of frequencies and pitches to identify the quietest sound you can hear for each frequency. By monitoring your hearing we can detect any deterioration that may be related to the workplace
The hearing test may take place in a sound booth or in a very quiet location.
You will be required to wear headphones and asked to push a button every time you hear a noise. You will hear a series of pips that may be easy to hear sometimes and then very faint at others; the tones may be low, medium, or high pitched. The test takes about 10 minutes, the object of the test is to find out the very faintest sound you can hear
The machine will then collate this information and using your gender and age group, a clinician will interpret if any hearing loss is indicated.
Sometimes the readings can be affected by infection, wax in your ear canals and background noise. Prior to starting the test we will examine your ears to check the ear drum and look for the presence of any wax as this may affect the results of the test
If any hearing loss is detected, we can then give advice on protective measures or if you need further investigations.
