Noise Reduction Rating

Earplugs have a noise reduction rating from 20 to 36 dB. 

The Environmental Protection Agency has a noise reduction rating (NRR) and labeling standards for hearing protectors.These standards provide a reliable way to rate hearing protectors. As noted, the performance also depends on fit. NRR applies to continuous noise and may not represent the noise reduction from impulse noise. A NRR of 10... 

The provision of each overexposed employee with an individually fitted hearing protector with an adequate noise reduction rating. 

Noise Reduction Rating—A rating given as a laboratory based indicator of the relative effectiveness of hearing protectors. 

Noise Reduction Rating or NRR — all hearing protectors carry a label indicating the NRR a higher number on the label means more effectiveness. 

The Environmental Protection Agency (EPA) developed the noise-reduction rating (NRR) as a method of gauging the adequacy of a hearing protectors noise-reducing capacity. The NRR equates to the amount of decibels by which a device reduces noise exposure. When exposed to a TWA of 100 dB and the worker wears a pair of earmuffs with a NRR of 26, the calculated actual exposure would be 74 dB. 

The Veratti ear muff combines comfort and style with protection. This lightweight product with head band padding and cushioned ear cups is perfect for wearing for extended lengths of time. With a noise reduction rating of 26 db, ambient noise is cut while still allowing for conversation. Comfort. All day long. Encon Safety Products, www.enconsafety.com. Circle 272... 

In addition, they are usually constructed without isolation valves on the fuel supply lines. As a result the final connection in the pipework cannot be leak-tested. In practice, it is tested as far as possible at the manufacturer s works but often not leak-tested on-site. Reference 32 reviews the fuel leaks that have occurred, including a major explosion at a CCGT plant in England in 1996 due to the explosion of a leak of naphtha from a pipe joint. One man was seriously injured, and a 600-m chamber was lifted off its foundations. The reference also reviews the precautions that should be taken. They include. selecting a site where noise reduction is not required or can be achieved w ithout enclosure. If enclosure is essential, then a high ventilation rate is needed it is often designed to keep the turbine cool and is far too low to disperse gas leaks. Care must be taken to avoid stagnant pockets. 

In addition, the noise reduction procedure can be switched off, resulting in significantly higher information rate but poor image quality. 

Figures 7, (b) and (c) depict the trade-off between the information rate and the visual quality of the printed watermarked image. Typical values of these parameters (for a 512x512 pixels image) range from N=270, E=8, n/k=15 5, noise reduction on , for an invisible hardcopy watermark application as in Figure 7 (b) to N=800, E=20, n/k=15 l 1, noise reduction off for high rate but obvious watermark signal as in Figure 7 (c).

When sound waves come in contact with a boundary obstacle, such as a wall or door, a portion of the sound wave energy is reflected, a portion is transmitted through the obstacle, and the rest is absorbed by the obstacle. One of the standard methods of measuring the effective sound absorption coefficient of an acoustical material is by finding its effect on the reverberation time, or decay rate, of the sound pressure level in the sound chamber. The total sound absorption in the receiving room is required to determine the noise reduction of the specimen being tested. The key here is to rule out the absorption of sound waves within the chamber that may be attributed to the door being tested. 

STC values are used to define the performance requirements for achieving a specified reduction in sound transmission from a source room to a receiving room. The STC rating of an installed door also determines how much noise reduction is possible between a given source room and receiving room. 

Figure 2.28 Simulation of a three-state single-molecule protein folding experiment in which the FRET value changes abruptly between 0.3, 0.5 and 0.7. The overall count rate is 1000 Hz. (a) Simulated data, acceptor in black and donor in gray, (b) Simulated data after filtration with the filter, (c) FRET efficiency calculated from a. (d) FRET efficiency calculated from b. (e) Histogram of the FRET efficiency values of c. (f) Histogram of the FRET efficiency values of (d).(Reprinted from Haran, G, Noise reduction in single-molecule Fluorescence trajectories of folding proteins. Chemical Physics 307 (2004) 137-145. (Copyright (2004) with permission from Elsevier.))...

Figure 11 A quantum-beat laser scheme with dynamical noise reduction. Quantum-beat is created by using a microwave field to couple the two closely spaced states 1> and 2). Atoms are pumped incoherently from the ground state 0> to the top state 3) with rate A, emit photons into two lasing modes (ai 2) on the 11,2)- 3> transitions, and then return to the ground state at rate 72.

Noise Reduction Coefficient (NRC) Single number, obtained as an average over low and high frequencies, rating tire soimd absorption of a material. 

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