Term
What is the goal of noise control? |
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Definition
To treat the dominant noise sources that add to TWA exposures of 85 dBA and above |
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Term
What is the biggest challenge of noise control? |
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Definition
IDing the primary noise source |
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Term
How much can time weighted averages be reduced & what is the associated cost? |
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Definition
Typical attenuation from HPDs is about 10 dBA. Cost depends on the type of industry. |
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Term
Benefits of Noise Control: 1. reduces the potential for ____ 2. may reduce ___ of other parts of the HCP 3. may reduce ___ & legal costs 4. improves ___; requires less vocal effort 5. ___ accidents/injuries/absenteeism 6. may reduce ___ ___ disease 7. Reduces ___ and increases productivity |
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Definition
ONIHL; costs; compensation; communication; reduces; coronary heart; errors |
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Term
Costs of noise controls depend on the type of ___ |
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Definition
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Term
-When workers are exposed to hazardous noise levels above 90 dBA TWA, OSHA requires using feasible ___ or ___ noise controls. -Impulse or impact noise should be controlled so it does not exceed ___ dB peak SPL |
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Definition
engineering; administrative; 140 |
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Term
What professions are involved with noise control? |
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Definition
occupational health professionals, plant engineers, and noise control engineers |
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Term
What are some common sources of noise? |
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Definition
mechanical impacts, high velocity air flow (air valves), high-velocity fluid flow (pipelines), and vibrating machine surfaces or products (food processing or glass manufacturing) |
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Term
Ways to Treat the Path: -Use ___ enclosures or barriers since reflections from walls, floors, & ceilings can increase levels generated by a source -Effectiveness of an enclosure is related to its ___; materials with higher mass are better (reduce more noise) -Barrier used depends on the ___ content of the noise |
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Definition
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Term
What is an example of a barrier or shield? |
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Definition
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Term
A higher sound transmission class (STC) means ___ sound is blocked |
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Definition
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Term
You can treat the source of sound by ___ ___ |
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Definition
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Term
devices put into the path of a flowing medium (e.g. air) to reduce sound levels. |
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Definition
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Term
What is an example of a silencer? |
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Definition
A muffler can decrease noise from vehicles’ exhaust pipe |
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Term
What are the 3 types of silencers? |
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Definition
Dissipative, reactive, and combination |
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Term
Dissipative Silencer/Muffler: -Dissipative/absorptive: use ___ materials to absorb sound |
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Definition
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Term
Reactive Silencer/Muffler: -Reactive/reflective : use big changes in ___ & sound ___ to decrease noise in a pipe -Ex: Inlet pipe of the silencer has lots of tiny holes, then sound goes to the expansion chamber. When the sound goes into the bigger cavity, the waves reflect off of the sides of the shell & ___ with incoming sound waves (fig. 3.2)[image] |
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Definition
impedance; reflection; interfere |
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Term
Combination Silencers: -Combines ___ & ___ components -Includes a layer of ___ on the outer shell of the reactive silencer -More noise abatement ___ frequencies -___ applications |
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Definition
dissipative; reactive; fiberglass; across; Limited |
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Term
Active noise cancellation may be used with passive silencers: -Provide good ___ frequency attenuation; not good for sounds above ___ Hz -Works well if air has ___ and/or particles |
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Definition
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Term
Outer surface of pipe is wrapped in sound absorption material then covered with a barrier material; used when silencers isn't an option |
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Definition
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Term
___ ___ operations can reduce noise. Ex: ?? |
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Definition
Proper machine; follow directions on how to operate it and running it at a lower speed than recommended can reduce noise |
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Term
What are some materials with high absorption coefficients? |
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Definition
Heavy carpet on foam rubber, polyester urethane foam (1 inch thick), and sprayed on cellulose fiber on timber lath |
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Term
Examples on treating the receiver? |
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Definition
Enclosures, hearing protection, administrative noise controls (rotate work force to decrease total noise exposure for individuals), and provide adequate break times |
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Term
pressure fluctuations of a medium that has elasticity and viscosity |
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Definition
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Term
pressure (p) variations above & below ambient atmospheric pressure; amount by which instantaneous pressure varies from atmospheric pressure |
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Definition
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Term
-pressure oscillation (in air) is ___ ___ -oscillation (in solids) is ___ |
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Definition
sound pressure; vibration |
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Term
Sound pressure can be generated by.... |
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Definition
-Impact -Pressure fluctuations in turbulent fluid flow -Vibrating surfaces |
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Term
distance traveled by sound wave during one pressure cycle |
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Definition
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Term
physical number of oscillations in a wave |
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Definition
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Term
SPL decreases by 6 dB when the distance from the source is ___ |
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Definition
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Term
What does p stand for and Pref stand for? |
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Definition
p=measured sound pressure and Pref=reference pressure=20 uPa |
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Term
What is the equation for SPL? |
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Definition
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Term
Pressure: -#dB=20 X log (__/__) |
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Definition
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Term
What does Po and Pr stand for? |
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Definition
Po=pressure output and Pr=pressure reference=20 micropascals |
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Term
logarithmic unit that describes a ratio |
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Definition
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Term
The Decibel: -The ratio may be in ___ or ___ (intensity) |
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Definition
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Term
A measure of total noise radiated by equipment in all |
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Definition
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Term
Power per unit area is Intensity: -Acoustic power is ___ distributed over a sphere when it is radiated from a point source -The resulting sound power per unit area of sphere is ___ (in watts/m^2) -There is no practical way to directly ___ sound power |
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Definition
evenly; intensity; measure |
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Term
Units of Measure for Power & Pressure: -Sound power (W) is the ___ ___ ___ from a source in watts (w) -reference level for power (intensity) is ________ -Sound pressure (p) is a force per unit area expressed in ____ or (N/m2) -reference level for pressure is ___ microPascals |
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Definition
total acoustic output; 10^-12 watts/m2; Pascals (Pa); 20 |
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Term
The Decibel in Measurements from a PO WER Reference: -#dB IL = 10 * log __/__ |
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Definition
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Term
What does WO and WR stand for? |
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Definition
Wo=watt/cm^2 (power) output Wr=watt/cm^2 (power) reference |
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Definition
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