Noise Production

TABLE 9.9 Recommended Air Velocities to Ensure an Economic Minimum of Noise Production... 

Apart from the energy constraints due to the friction losses, the main reason for limiting the air velocities in ducts is to reduce noise production. Some recommended air velocities are given in Table 9.9. 

Another problem is the ease with which a DSC apparatus degrades. Briefly, after it is used for a long time, it begins to produce noise, such that no definite DSC curve can be obtained. This may be attributable to the contamination of cell holders by gas from samples. The authors have conducted experiments with sealed cells by passing nitrogen gas through them, but contamination and its related noise production could not be avoided. For a time, a DTA apparatus considered less prone to contamination was borrowed from Nippon Kayaku Co., Ltd. and used for investigative purposes. 

There are four major mechanisms of noise production in combustion equipment. They can be categorized as predominantly high frequency or low frequency sources. They are ... 

Disadvantages of high-volume samplers are High power consumption, high noise production and in some cases contamination of the particulate samples by abrasion products of the pump have been reported (Countess 1974). 

Another consideration is the beam cross section. Typical beam cross section at SSRL (SPEAR ) is on the order of several to tens of mm, while that on typical APS lines is in the tens of microns. For practical sample size, e.g., 2 cm, this means that the beam size cannot be larger than about 40 pm at a critical angle of 2 mrad. Any larger part of the beam will miss the sample (Fig. 6) and probably incur dramatic noise production. In practice this greatly reduces the utility of the GI experiment as so much incident beam is rejected by collimation (e.g., with SPEAR with a 2 mm vertical height beam, 98% of the beam is discarded). Thus the APS beams are ideal for samples of this size, and all of the output from an insertion device can in principle be directed on a GI sample of a few mm. 

The sound level given in the previous section can be regarded as an upper limit of stochastic bubble sound. In respect to noise levels from cavitating ship propellers of aproximately 150 dB and flow noise of 40 dB, it can be concluded that this noise production lies somewhere in between the two forementioned ones. 

Long life, high reliability, no maintenance needed Low radio frequency interference and noise production... 

Potassium chlorate is truly a unique material. Shimizu has stated that no other oxidizer can surpass it for burning speed, ease of ignition, or noise production using a minimum quantity of composition. It is also among the very best oxidizers for... 

Scientific research on noise affecting the environment, methods for noise-level reductions, low-noise techniques, and development of special low-noise products are... 

These are the types of economic measures that are or could be used within the policy of fighting noise they include tax payments and noise emission payments, economic stimuli as the motivation to reduce noise and develop low-noise products, and compensation payments to those exposed to noise. 

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