Noise Flashcards
(157 cards)
1
Q
What is the purpose of the Eustachian tube?
A
releases pressure inside the ear by draining fluid into the throat
2
Q
Describe the outer ear
A
outside of ear to the eardrum, channels and directs sound to the ear drum
3
Q
What is the visible part of the ear and what is its purpose?
A
pinna
4
Q
what is the purpose of the middle ear?
A
transfers sounds into electrical impulses
5
Q
What is another name for the eardrum?
A
tympanic membrane
6
Q
What is the purpose of the bone in the ear?
A
Bone transmits vibrations
7
Q
What are some conditions that can impact the pinna?
A
Sunburn, frostbite, cauliflower ear
8
Q
What are conditions of the ear canal?
A
packed wax, foreign objects, otitis (infection of the ear canal)
9
Q
What are conditions of the ear drum?
A
Perforation or rupture (diving, blows, explosions)
10
Q
What are conditions of the eustachian tube?
A
swelling, obstruction (allergy or infection)
11
Q
What are conditions of the middle ear?
A
Bacterial infection, fixation of bones (bone disease)
12
Q
What can cause damage to the chochlea?
A
infection, toxins, excessive vibrations, heavy metals, organic solvents, CO, noise induced hearing loss, age induced hearing loss
13
Q
What are conditions related to the vestibular system?
A
labyrinthitis (vertigo, nausea, vomit), tumors
14
Q
What is occupational hearing loss?
A
hearing impairment in one or both sides from one’s employment
15
Q
What is acoustic trauma?
A
Injury to inner ear produced by one or few exposures to sudden intense acoustic forms of energy (explosions or blasts)
16
Q
What is noise induced hearing loss?
A
Cumulative permanent loss of hearing developed over months or years of exposure
17
Q
What factors determine duration and severity of hearing loss?
A
1) Sound level
2) Frequency of sound
3) Duration of sound - longer duration worse
4) Temporal distribution
5) Type of sound energy
6) Individual genetic and age factors
7) concurrent exposure to ototoxic compounds
18
Q
What sound levels will make hearing loss more severe?
A
sound levels >60-80 dB
19
Q
What frequency will make hearing loss more severe?
A
500- 200 Hz
20
Q
Give examples of types of sound energy
A
Continuous vs. intermittent
21
Q
What is sound?
A
any pressure variation that the human ear can detect. it produces a sensory response in the nerves
22
Q
What is noise?
A
Sound that bears no information, often unpleasant and likely harmful
23
Q
What are sound waves?
A
Vertical, vibrating plate causing small, repeated fluctuations in atmospheric pressure which propagate to the eardrum causing it to vibrate
24
Q
Describe the frequency of sound (f)
A
number of times per second that an air molecule is displaced from its position of equilibrium, rebounds in opposite direction and returns to equilibrium
Horizontal distance between peaks
25
How is frequency measured?
Hertz (Hz)
26
How is frequency perceived?
pitch (high frequency noise is more annoying)
27
Draw the physics of sound
see slide
28
What would be the frequency of a soundwave with 2 cycles in 1 second?
2 Hz
29
What is amplitude?
loudness
30
What is frequency?
pitch
31
What is wavelength?
distance between two analogous points on two successive parts of wave- Distance a sound wave travels in one cycle
32
What is the velocity of sound?
speed of sound
always equal to product of wavelength and frquency
33
What is the equation for velocity?
c=f(wavelength)
velocity = frequency * wavelength
see slide to wavelength symbol
34
What is sound pressure?
Variations in atmospheric pressure that are detected by eardrum
35
How is sound pressure measured?
micropascals
N/m2
microbars
dynes / cm2
36
What are the common conversions for sound pressure?
1Pa = 1 N/ m2 = 10ubar = 10d/cm2
37
What is the decibel?
unit of sound - minimum perceptible difference i loudness
38
How does a decibel relate to a bel?
1/10 of a bel
39
What is intensity?
sound power, measure in W/m2
40
What happens to intensity as you move away from the source?
Diminishes with distance
41
What is a problem with intensity?
hard to measure
42
What tool measures sound pressure?
Sound level meters
43
What is the symbol for sound pressure level?
Lp
44
What is the unit for sound level pressure?
dB
45
What type of agent is noise?
Physical agent
46
What is the major concern with noise?
It can cause permanent hearing loss (permanent threshold shift)
47
What threshold shift can occur after one loud incident or minor blast?
temporary threshold shift
48
Hearing loss factors
- sound pressure level
- frequency of sound
- duration of exposure
49
What are the types of hearing loss?
```
Conduction
Sensorineural
Temporary vs. permanent threshold shift
Tinitus
trauma
```
50
Describe conductive hearing loss
- blockage, damage to eardrum
| - not due to noise in most cases
51
Describe sensorneural hearing loss
- damage to inner ear or nerve
| - chronic noise exposure does this
52
What is damaged by noise?
Hair cells
53
What are some of the problems with noise?
1) Distraction of workers --> accidents
2) Interference with communication --> accidents
3) Annoyance--> stress or violence
54
When is a hearing conservation program required?
>85 dB over 8 hours
55
What is the goal of the hearing conservation program?
to prevent hearing impairment as a result of noise exposure on the job
56
What are the 5 components of the hearing conservation program?
1) exposure monitoring
2) audiometric testing
3) hearing protection
4) employee training
5) record keeping
57
What is the rationale for HCP?
- 20-30 million workers are at risk of irreversible hearing loss due to exposure and noise
- 9 million other workers are at risk of hearing loss from exposure to ototoxins
- to save on workers compensation costs
58
What are examples of ototoxins?
organic solvents, metals, CO
59
Name some elements of the hearing conservation program
- protect and conserve hearing
- person in charge
- measure baseline and ongoing exposure
- control of excessive exposure
- audiometric testing
- training
- SOP
- Program assessment
- Records
- Buy quiet
- other exposures
Main idea: develop the BEST program, not the required one
60
What are environmental risk factors for hearing loss?
- SPL of noise (intensity)
- Frequency of noise (type of noise)
- period of exposure (work duration)
- total work duration
- surroundings (noise reflected or absorbed)
61
What is the most important environmental risk factor?
Surroundings
62
What are host factors that impact hearing loss?
- distance of work situation from noise source
- position of worker's ear due to work station
- years of employment
- individual susceptibility
- age
- co-existing loss or disease
- exposure outside of work
63
What are the most important host risk factors for hearing loss?
1) Age
| 2) Coexisting loss or disease
64
What equipment can be used to measure noise?
- sound level meters
- octave band analyzers
- noise dosimeters
65
What are the differences between sound level meters, octave band analyzers, and noise dosimeters?
Sound level meters: area- measure sound pressure variation in the air
Octave Band Analyzers: Area, brake noise down in frequency components for complex situations
Noise Dosimeter: Personal measurement- exposure monitors logging noise energy
66
What are the components of the meter?
- Microphone
- Amplifier
- Weighting Scale
- Output
67
What is the role of the microphone in a sound level meter?
Responds to sound pressure variations and produces and electrical signal
68
What is the role of the amplifier in the sound level meter?
Increases the output signal
69
What is the purpose of the weighting scale in the sound level meter?
electronically adjusts the amplification of frequencies giving some more amplification than others
70
What are the different weighting scales?
Flat, A, B, C scales
71
What is the most common weighting scale for sampling and why?
A, because OSHA standards are in the A scale (dBa)
72
What is the purpose of the output in sound level meters?
Digital display that shows dB
73
What can time weightings be set to?
fast, slow, or impulse
74
What determines how you set your time weighting?
how quickly you want the meter to respond to changes in sound
75
What can noise dosimeters determine?
- % of allowable exposure
- instantaneous current SPL
- Peak sound SPL
- Time History ** of exposure
- SPL average
- TWA*** sound pressure level
76
Name some work processes that would create noise levels above 85 dB
- Hand drill
- Chain Saw
- Belt Sander
- Table Saw
77
What is the threshold or threshold gate?
-lower limit of what SPL will be included
78
What is the criterion level?
OSHA standard of 90dBA, used to determine % of allowable exposure, it is the & of the criterion
79
Who is it important to interview for their ideas?
workers
80
What observations should be made while noise sampling?
- position relative to sources
- exposure and time
- obvious worker hearing problems
- noise source information
- surface materials
- controls & feasibility
81
Considerations for noise sampling
- diagrams
- locations of sampling/ workers
- data sheets
- checklist (NIOSH)
- Observations
82
What is the exchange rate?
Sound pressure increase or decrease that determines a halving or doubling of exposure time
83
What is another name for exchange rate?
doubling rate
84
What is the OSHA exchange rate?
5 dBA
85
What is the NIOSH exchange rate?
3dBA
86
Who follows the NIOSH exchange rate?
EPA, EU- 3dBA
87
Which exchange rate is based on physics?
NIOSH- 3 dBA
88
What is the DOD exchange rate?
4 dBA
89
What is sound power
total sound energy emitted by a source er unit time
90
Lw=10logW/Wo
What is W? Units?
Sound power (watts)
91
Lw=10logW/Wo
What is Wo? Units?
reference power (10^-12 Watts)
92
Lw=10logW/Wo
What is Lw?
Sound power level (dB)
93
What is the short method for adding decibels?
Use the table
94
0-1 dB difference =
+ 3 dB
95
2-3 dB difference =
+2 dB
96
4-9 dB difference =
+1 dB
97
10 dB or more difference
+0 dB
98
What is the equation for the TWA for noise?
Dose % = 100 [(C1/T1)+(C2/T2)+...]
99
Dose % = 100 [(C1/T1)+(C2/T2)+...]
What is the units for dose?
%- not units
100
Dose % = 100 [(C1/T1)+(C2/T2)+...]
What are the Cs?
individual exposure time (hours) at specific sound pressure levels
101
Dose % = 100 [(C1/T1)+(C2/T2)+...]
What are the Ts?
Allowable exposure time (hours) at specific sound pressure levels- find on OSHA site (or use NIOSH table based on exchange rate of 3dB)
102
Is TWA for sound the same as TWA for airborne agents?
NO
103
What is the alternative to expressing dose as a percentage?
express as a decimal
104
How does dose in decimal form compare to exposure standards?
>1- overexposed above either the PEL or REL
| >.05- above the action limit for OSHA (if using OSHA exchange rate)
105
If dose is expressed in %, what is the percent for over exposure? and percent for action limit?
>100% & >50%
106
How long can someone stay in an area of a given SPL- equation
tallowed = T/ [2(Lp-Lcrit)/x]
107
tallowed = T/ [2(Lp-Lcrit)/x]
What is tallowed?
allowable exposure time (hours)
108
tallowed = T/ [2(Lp-Lcrit)/x]
What is T?
Base period, ususally 8 hours
109
tallowed = T/ [2(Lp-Lcrit)/x]
What is Lp?
Sound pressure level dBA
110
tallowed = T/ [2(Lp-Lcrit)/x]
What is Lcrit?
Criterion level (dBA)
111
What is x?
exchange rate (dBA)
112
When comparing to OSHA standards, what action should be taken if dose >85dBA?
baseline measurements & annual audioprograms
PPE required
113
Per OSHA standards, if PEL >90dBA, what actions are needed?
Noise control program
- engineering and administrative controls to reduce exposure to <90 dBA
114
Per OSHA, at what point is PPE required? At what point is PPE no longer adequate?
>85 dBA, >90 dBA
115
What can you do at the source for noise problems?
- Modify
- Redesign
- Relocate
116
What can you do at the path level for a noise problem?
- enclosure
- absorption
- barrier
117
What can you do on the receiver end to reduce noise exposure?
- enclose
- absorption
- relocate
118
What is the cost of controlling noise at the source compared to controlling noise at the path?
1/10th the price to control noise at the source
119
What type of agent are the sources?
typically mechanical (vibrating or moving surfaces)
120
Why is sound considered to be aerodynaic?
unsteady flow of air, specific gas, or stream
121
How do you solve mechanical noise?
minimize the change of force (impact)
122
How do you solve aerodynamic issues with noise?
Minimize pressure changes/ turbulence
123
What are engineering controls for noise?
- use a quieter machine, process, or materials
- enclose the source
- decrease vibration
- decrease energy
- decrease driving force
- change directivity?
124
Name specific engineering controls to control noise problems from mechanical sources
- change the structure/ material of the source
- lubricate to decrease friction
- insulate (lagging)
- dampen the source
- Brace the source
- Decrease vibrating area**
- decrease resonance
- reduce dropping height
- decrease rotational speed
- improve the dynamic balance
- isolate vibration
125
What must you consider when enclosing the source of mechanical noise?
heat build-up
126
Give example of decreasing vibrating area
- using multiple belts instead of 1 thick belt
127
How does damping and bracing work as a control for mechanical noise?
makes the source stiffer and reduces vibrations
128
Give an example of insulating the vibration?
Add rubber around solid connecting arts
129
How is isolating vibration different than enclosing?
enclosing places machinery in room or area, isolating would be like putting up a noise barrier
130
Where there is turbulence, there is...
noise
131
What are engineering controls for aerodynamic noise?
- increase absorption of sound
- decrease reflection
- decrease reverberation
- increase distance from source to worker
- mufflers
- block the path with baffles
- enclose the worker
132
What do you need to increase absorption of sound/ decrease reflection, and decrease reverberation?
change of materials
133
What is an engineering control at the path level for noise?
- Increasing the distance
| - Active noise control
134
By doubling the distance, you decrease SPL by...
6dB
135
How does active noise control work?
device generates a sound wave opposite or anti-phase of the source sound wave
136
Destructive interference --> ?
attenuation
137
What are administrative controls of noise?
- schedule noisy activities when fewest people are present
- rotate workers between quiet jobs & noisy jobs
- have very quiet rest areas and lunch areas
138
What are additional strategies to prevent noise exposure?
optimize preventative and emergency maintenance
| - use specifications to buy quiet
139
What are two types of PPE to prevent noise induced hearing loss
- muffs (around outer ear)
| - plugs (in ear canal)
140
How should you select PPE?
Select type based on noise and worker
Based on noise reduction rating
141
What NRR should you chose?
NRR with highest NRR
142
What NRR difference is meaningless?
<3 dB
143
Who gives the NRR for devices?
manufacturer
144
How do you determine the noise reduction from the NRR rating?
subtract 7, divide by 2, and add to env measurement
145
What are the limitations of NRRs?
Measure based on optimal conditions and trained workers
146
When do you require plugs & muffs?
>105 dB
147
If there are multiple noise sources and noise is above 105 dB
take higher NRR and add 5 dB
148
What is the name for medical monitoring for hearing?
audiometry
149
What audiometry measurements do you need to take?
- pre-placement
- baseline
- annual
150
What does audiometry determine?
threshold for each ear and different frequencies
151
What is the requirement before the test?
Should be in quiet area 14 hours before test
152
What is the instrument for audiometry?
audiometer
153
Where is audiometry measured?
audiometric booth
154
What are the prescribed frequencies for audiometry testing?
- 500
- 1000
- 2000
- 4000
- 8000 Hz
155
What audiometry devide givs data?
audiogram
156
What considerations must be taken when analyzing results from audiometry?
- adjust for age
| - compare to past thresholds
157
What is the standard threshold shift?
if average of losses at each frequency is greater than or equal to 10 dB
