Noise exposure Flashcards
What is NIHL? (noise induced hearing loss).
It is the type of hearing loss associated with noise damage or acoustic trauma. Ex (gunfire, military, machinery, concerts, explosions, etc).
NIHL is also known as:
Man made hearing loss
What is TTS and PTS?
- TTS (temporary threshold shift): noise exposure that can cause hearing thresholds to shift for an amount of time and return back to normal).
- PTS (permanent threshold shift): noise exposure that can cause hearing thresholds to shift permanently.
What are 3 symptoms associated with NIHL?
- Tinnitus
- Hyperacusis
- Abnormal pitch perception
What is the primary site for of lesion for gradual NIHL?
Outer hair cells (OHCs)
Which frequency region is affected first?
The high frequencies (mainly 3-6kHz with 4kHz having the worst hearing loss).
OHCs are affected when there is a 40-60 dB hearing loss, at what point do the IHCs get affected?
When there is prolonged exposure and the hearing loss exceeds 60 dB HL.
What is the difference between dBA and dBC? Which scale do we use and why?
Both dBA and dBC are based on the loudness curves.
- dBA needs 40 dB SPL = 40 phons at 1kHz
- dBC needs 100 dB SPL = 100 phons at 1kHz.
Because dBC needs 60 dB SPL more, we don’t use it because it is too loud. It is most appropriate to use dBA.
What are 5 important aspects of hearing conservation programs?
- Noise reduction efforts
- Measurement of noise exposure
- HPDs (hearing protection devices)’
- Audiometric surveillance
- Education of workers
What are the two types of exchange rates (noise)? Which one do we use in Canada?
- 5 dB exchange rate
- 3 dB exchange rate, we use 3 dB
How many hours can someone be exposed to at 85 dBA?
8 hours
How many hours can someone be exposed to at 94 dBA?
1 hour
Can someone be exposed to 100 dBA? How much time would they be able to be in that condition?
15 minutes
When TTS occurs, what happens in the cochlea?
The tip links break between the OHCs and they lose contact with the tectorial membrane. This can cause a reduction in blood flow of the cells, but once removed from the sound environment they can heal.
When PTS occurs, what happens in the cochlea?
An overexposure of noise can lead to metabolic changes in the cells and results in loss of oxygen (hypoxia) causing the cells to die.
How many OHCs and IHCs do we have?
12k OHCs and 4k IHCs
Is NIHL bilateral or unilateral?
It is usually bilateral but sometimes can be unilateral in the following conditions (guns, driving with windows open, etc).
What is a noise level map?
It is a map used in a work industry that can indicate the noise levels in a specific area on the floor
What is a dosimeter
A piece of equipment used to measure sound exposure in work areas
What is an acoustic trauma?
A single-occurrence that cause a permanent hearing loss (ex. grenade, fireworks, speaker blown off)
What is PEL and REL
- Permisible exposure level: what is technically allowed.
- Recommended exposure level: what is recommended based on personal and work factors.
How does audiometric testing work for hearing conservation programs?
A baseline audiogram needs to be done within 6 months of first exposure, needs test done annually. If there has been a change, need to retest within 30 days.
How long are records kept if employment ends?
At least 2 years
What are the two types of HPDs and which one is better?
- Earmuffs: they enclose/encase the whole ear.
- Earplugs: placed inside the ear canal.
Earmuffs are better as they provide the most protection by covering the whole ear.
What is REAT and MIRE?
- REAT (real ear attenuation threshold): thresholds obtained with and without hearing protections.
- MIRE (microphone in real ear): place a probe tube in ear with ear protection and another outside of ear, check difference between the two.
What are the two compensation programs that cover noise damage in Ontario?
- VAC (veterans affairs canada)
- WSIB (workplace safety insurance benefits)
Which frequencies are used to compared the baseline audiogram and the annual audiogram with noise exposure?
2000, 3000, 4000 Hz
What is TWA?
Time-weighted average.
Usually in 8 hour periods - the average time in noise.
