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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Term
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Definition
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