Noise Induced Hearing Loss Flashcards
What is PTS?
Permanent Threshold Shift - gradually develops, hearing loss is cumulative throughout one’s life. Remaining hearing loss following incomplete recovery from TTS
What is TTS?
Temporary Threshold Shift - temporary hearing loss after noise exposure caused by broken tip links between OHC stereocilia, loss of contact betwen stereocilia and tectorial membrane, swelling of auditory nerve fibers, and reduction in cochlear blood flow.
What is STS?
Standard Threshold Shift - average hearing sensitivity at 2000, 3000, and 4000 Hz is 10 dB worse at annual test compared to overage obtained on baseline audiogram
What is TWA?
Time Weighted Averages - integrated levels used for 8 hour measurements of noise exposure
What are the different dBs?
dBA - based on 40 phon curve; similar to dB SPL
dBC - similar to unweighted dB SPL; more appropriate to measure noise level
What is apoptosis?
Normal active process; organisms frequently undergo this pruning process and serves purpose such as defense against cancer cells
What is necrosis?
Passive pathologic process; accompanied by inflammation and rupture.
Occurs from acoustic trauma.
What are the exchange rates?
3-dBA, NIOSH
5-dBA, OSHA
Describe acoustic trauma
What is NIOSH?
National Institute for Occupational Safety and Health - makes recommendations of best practice exposure limis
What is OSHA?
Occupational Safety and Health Administration - government agency uses public rulemaking to set mandatory exposure limits
What is PEL?
Permissable Exposure Limit - specifies a TWA exposure limit of 90 dBA over an 8 hour workshift with 5-dB exchange rate. Employers must attempt to reduce noise exposures above 90 dBA TWA through noise controls (OSHA raised to 100 dBA)
What is REL?
Recommended Exposure Limits - set by NIOSH with 3 dB exchange rate
T/F: there is LESS blood perfusion in the APICAL end of the cochlea compared to the BASE: which makes high frequencies susceptible
False
T/F: Max cochlear damage occurs at the frequency of max stimulation
False
T/F: Ear canal resonance plays a role in added auditory stimulation at 2-4k Hz
True
Noise exposure results in decline in hearing sensitivity at which frequency region?
3000 - 6000 Hz
NIHL severity depends on what two factors?
Intenstiy & Duration of exposure
OSHA’s allowable times are determined by noise levels measured with this
dB A
A better representation of how humans hear various frequencies at high-intensity levels
dB C
A 3-dB exchange rate means that the risk of NIHL is equal between an 8 hour exposure to 85 dBA noise and __________ hour noise exposure to _________ dBA noise
4 hour
88
A 5-dB exchange rate means that the risk of NIHL is equal between an 8 hour exposure to 85 dBA noise and __________ hour noise exposure to _________ dBA noise
4 hour
90
T/F: NIOSH is legally enforceable
False - OSHA is legally enforceable
T/F: OSHA makes recommendations
False - NIOSH makes recommendations
T/F: Only OSHA has noise dosage based on dBA TWA
False - both OSHA and NIOSH has noise exposure based on dBA TWA
T/F: OSHA is less restrictive than NIOSH
True
T/F: NIOSH uses 3-dB exchange rate
True
T/F: OSHA uses 5-dB exchange rate
True
What are the five standards of hearing conservation?
- Education of workers
- Hearing protection use
- Audiometric surveillance
- Noise reduction efforts
5.Measurement of noise exposure
What is an engineering control?
Mufflers, sound absorbing coatings or material to walls and ceiling
What is an administrative control?
Conducting noisy operations when there are the fewest workers nearby
Describe the noise exposure path
Sound source through transmission pathway to receiver
What can a TTS result from?
- Broken tiplinks between OHC and stereocilia
- Loss of contact between stereocilia and tectorial membrane
T/F: After TTS, audiometric thresholds return to pre-exposure level
True
T/F: Acoustic trauma results in TTS
False - acoustic trauma results in PTS
T/F: All auditory functions return to pre-exposure levels after TTS
False
T/F: After PTS, audiometric thresholds return to pre-exposure level
False
What are changes in body function (non-auditory symptoms) that occur as a result of noise exposure?
Cardiovascular disease (CVD)
Cognitive effects
T/F: Classical string instruments (violin, cello) generate sounds often exceeding 100 dBA
True
T/F: at 70-80% volume settings, using headphones or earbuds should be limited to less than 30 mins/day
False
T/F: adults and teenagers end to prefer listening at higher intensities when using earbuds compared to headphones
True
T/F: Ambient noise levels impact preferred listening level (i.e. adults tend to increase the intensity of music when in a noisy environment)
True - Lombard effect
Human hearing is most sensitive at what range of frequencies?
1000 - 5000 Hz
Why is there a notch at 4000 Hz?
The frequency of maximum cochlear damage is one half to one octave above the frequency of max stimulation.
Max stimulation for adult ears is roughly one half octave to one octave below 4000 Hz making 4000 Hz most susceptible to damage
T/F: many physical changes after TTS reverse and hearing sensitivity returns to pre-exposure baseline
True
What specific action is required in the presence of an STS?
Shift must be recorded and confirmed with a retest within 30 days of the company becoming aware of the shift. If the retest confirms the STS, the company must inform the worker of the hearing change with a written notification.
STS equal to or greater than ______ dB are required to be recorded on OSHA’s illness/injury log as soon as first identified. Recorded as category of occupational illness.
25
At which (3) points can noise exposure be reduced?
Source - where noise is generated
Along the pathway - where noise travels
Receiver - worker
What is the hierarchy of controls?
Traditional approach to reduce risk of health effects from environmental hazard.
- Eliminate noise source (most reliable/desirable)
- Substitute - replacement of high noise source
- Engineering controls - changes to the source
- Administrative controls - establish limits on exposure duration
- Personal protective equipment (least reliable/desirable) - use as needed
Which control is primary?
Source
