Industrial audiology Flashcards

Effect of noise on the auditory system, diagnosis of noise-induced hearing loss, non-auditory effects of noise, legislation and medico-legal aspects of NIHL

1
Q

What is the definition of noise?

A

-Unwanted sound
-Wanted sound e.g. music

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2
Q

What are the four types of noise?

A
  1. Steady-state noise- Continuous noise that does not vary by more than 5 dB over time, either gradually or rapidly e.g. workers operating machinery that runs constantly
  2. Fluctuating noise- Continuous that does vary by more than 5 dB over time, gradually or rapidly e.g. workers who move around within their work environment
  3. Intermittent noise- Non- hazardous noise mixed with hazardous noise e.g. workers using hand tools, turning equipment on and off
  4. Impulse noise- Contains rapid pressure transients, consists of single bursts with duration <1s and peak levels 15 dB higher than the background noise e.g. gunfire
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3
Q

What are the three measurements of noise?

A
  1. dB SPL- sound intensity
  2. dBA- takes into account intensity and how the human ear/ auditory system responds
  3. dBC- specifies peak or implace noise levels e.g. gunfire
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4
Q

Which measurement of noise is best correlated with the relative risk of noise induced hearing loss?

A

dBA because it takes into account the respose of the auditory system in addition to the sound intensity itself

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5
Q

What are the different noise injuries that exposure to loud sounds can cause?

A

-Temporary threshold shift
-Permanent threshold shift
-Tinnitus
-Hyperacusis
-Abnormal pitch perception

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6
Q

Who is specifically vulnerable to abnormal pitch perception following noise exposure?

A

Musicians

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7
Q

What are the factors influencing someone’s vulnerability to cochlear hearing loss as a response to noise exposure?

A
  1. Sound level of the exposure
  2. Duration of the exposure
  3. Spectrum of sound
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8
Q

What is the primary site of lesion of noise-induced cochlear hearing loss?

A

The death of the outer hair cells

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9
Q

Does noise-induced hearing loss occur rapidly or gradually?

A

-Generally noise-induced hearing loss happens following long-term exposure to moderately intense noise
-However it develops insidiously- therefore challenges with communication and changes in music perception are often not obvious until the degree of hearing loss is quite significant

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10
Q

Which area of the audiogram will likely be affected by a noise-induced hearing loss

A

-Typically effects region around 4 kHz initially
-Further exposure extends loss at lower and higher frequencies
-Hearing loss of 60 dB HL or greater
-Damage to IHCs and auditory nerve fibres

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11
Q

Aside from hearing loss, what problem is often experienced by people with noise-induced hearing loss?

A

Tinnitus

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12
Q

Why is a notch at 4 kHz specifically observed in noise-induced hearing loss?

A

-The frequency of maximum cochlear damage is 0.5 to 1 octave above the frequency of maximum stimulation
-Resonance amplifies sound by 15-25 dB a the resonant frequency
-Resonance in the ear canal/ pinna produces enhancement of frequencies around 2-4 kHz

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13
Q

Which end of the cochlea is the most vulnerable to noise?

A

-The basal end which is associated with high-frequency sounds
-This is because there is less blood perfusion/ oxygenation in the basal end of the cochlea compared to the apex

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14
Q

What is temporary threshold shift (TTS)?

A

-Experienced directly after noise exposure
-Hearing may be dulled and may experience tinnitus
-Recovery usually 16-48 hours post-exposure

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15
Q

What is a permanent threshold shift (PTS)?

A

-Gradual loss of hearing, combined with age
-Currently incurable

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16
Q

What is the relationship between TTS and PTS?

A

-TTS is not a predictor of PTS thus someone who demonstrates a large TTS following noise exposure is no more susceptible to permanent hearing loss later
-If a sound exposure is sufficient to cause a TTS then it is sufficient to cause a PTS

17
Q

What are the characteristics of noise-induced hearing loss (NIHL)?

A

-Always sensorineural hearing loss
-Often bilateral and symmetrical
-Does not produce a profound loss
-Once the noise exposure stops the hearing does not continue to deteriorate
-Rate of loss decreases as thresholds increase
-Most severe at 4 kHz
-Maximum loss is seen after 10-15 years after exposure
-Continuous noise more damaging than intermittent noise

18
Q

When is noise-induced hearing loss not bilateral and symmetrical?

A

In the case of gunfire where the gun is one side or only one side is being protected

19
Q

At what sound level does hearing damage begin?

A

85 dB

20
Q

With ever ____ dB increase in the noise level, the duration of permissible exposure becomes ____

A

-3 dB
-Half

21
Q

What are some non-auditory effects of noise?

A

-Hypertension
-Heart disease
-Annoyance
-Sleep disturbance
-Stress

22
Q

What is the procedure for hearing tests administered for the purpose of meeting the requirements of the Health and Safety Executive for those exposed to noise at work?

A

-Air conduction testing without masking
-Testing starts with the better ear and at 1000 Hz
-Then test 2000 Hz, 3000 Hz, 4000 Hz, 6000 Hz, 8000 Hz and 500 Hz
-Retest at 1000 Hz- if retest value is no more than 5 dB different from the original take the more sensitive threshold as the final value