Sound emission

ASME Gas Turbine Installation Sound Emissions B133.8 Published 1977 (Reaffirmed Year 1989)... 

This standard gives methods and proeedures for speeifying the sound emissions of gas turbine installations for industrial, pipeline, and utility applieations. Ineluded are praetiees for making field sound measurements and for reporting field data. This standard ean be used by users and manu-faeturers to write speeifieations for proeurement, and to determine eom-plianee with speeifieation after installation. Information is ineluded, for guidanee, to determine expeeted eommunity reaetion to noise. 

A. Thomas and G.T. Williams. Elame noise Sound emission from spark-ignited bubbles of combustible gas. Proc. R. Soc. Lond. A, 294 449 66,1966. 

M. Katsuki, Y. Mizutani, M. Chikami, and Kittaka T. Sound emission from a turbulent flame. Proc. Combust. Inst., 21 1543-1550,1986. 

Ultra-sound emissions typically occur when male rodents are exposed to female odours or altricial neonates to maternal sources (Whitney, 1974 Conely and Bell, 1978). Without the VNO, sexually inexperienced male mice do not utter emissions at ultra-high frequencies (UHF), whereas those with prior experience vocalise after VN-x, as discussed above (Chap. 5). Female mouse urine contains a unique UHF-eliciting component which is non-volatile but ephemeral (Sipos et al., 1995). The signal is degraded by oxidation and disappears within 15 to 18 hours of deposition. Direct contact with freshly voided urine must occur before males will vocalise (sexually experienced or inexperienced). At least one of the olfactory systems is needed for UHF to be elicited by fresh urine complete deafferentation abolishes the response (Sipos et al., 1993). Exposure to females permits UHF to be elicited by other than chemical cues (Labov and Wysocki, 1989). Nocturnal or cryptic species conceivably use ultrasound to advertise male presence whether this is to deter other males or assist with female location is unclear. 

Greaves and Lamb (1971) observed sound emission from polyethylene film due to the electrostriction effect. 

Self-excited combustion instabilities are associated with the propagation and reflection of heat-release-induced acoustic waves and their interactions. Hence, flame sound represents the main source of these acoustic waves. Therefore, sound pressure level (SPL) data for turbulent nonpremixed jet flames have been obtained for two Turbulent Nonpremixed Flame (TNF) workshop flames, DLR-A and DLR-B [1]. The exit Reynolds numbers (Re) for the two flames based on injected gas properties at room temperature were 15.200 (DLR-A) and 22,800 (DLR-B). Air was used for studying the sound emission from equivalent nonreacting jets. The flow in each case had very low exit Mach numbers (M = 0.04-... 

J. J. Schroder, S. McGill, M. Dirbach, and F. Podzelny, Secondary Nucleation Ambivalent Heat Transfer and Sound Emission in Low Pressure Subcooled Boiling, in Proc EUROTHERM Semi-... 

Thomas, A., and Williams, G. T. "Flame Noise Sound Emission from Spark-Ignited Bubbles of Gombustion Gas." Proceedings of the Royal Society, A 294 (1966) 449. 

One of the main benefits of a premixed head in comparison with a diffusive head is the low noise emission at the stack. A premixed burner is generally quieter than a diffusive burner because of the lower combustion turbulence, on the condition there is no instability in the combustion, an instability that is possible with diffusive flames too. Figure 25.7 shows the comparison between the noise at the stack of the configurations previously examined. Like gas emissions, noise measurements are influenced by the combustion chamber type. Regarding sound emissions at the stack, the mat head still exhibits lower emissions in comparison with the metal sheet head as seen in Figure 25.8. 

Cavitation often occurs in hydrodynamical equipment. Our research is concerned about cavitation near ship propellers. Here cavitation causes erosion, lift oscillations and sound. The purpose of our research is eventually to find scaling rules for the sound emission of propeller models to full scale noise. Several types of cavitation can be distinguished, see for example Knapp, Daily and Hammitt [ 1]. The occurence of those types depends on, for example, the cavitation number, free stream velocity and the angle of incidence. Here a division as scotched in figure 1 will be given. 

TS involves the measurement of the sound intensity emitted by a sample as a function of temperature. Sound emission originates from the release of thermal stresses in the sample, such as movement of dislocations, generation and propagation of cracks, nucleation of new phases, relaxation processes, and discontinuous changes in physical properties. For example, at a glass transition temperature, a discontinuous change in free volume generates elastic waves... 

Acoustic emission testing n. A non-destructive test for determining material or structural integrity by detecting and recording location, amphtude, and frequency of sound emissions as test loads are applied. 

During thermal treatment, emission of light (electrical discharge from a dielectric material) or the mechanical relaxation (may be with the sound emission) in a stressed specimen can also be studied with the recorded time-... 

Noise. Sound emissions which amount to a molestation or pose a danger to man are perceived as noise and are regarded as negative environmental factors. Noise is a mixture of pressure waves of frequencies from between 18 and 20,000 Hz. 

Active structural acoustic control (ASAC) Reduced structure-borne noise and sound emission/imission, increased passengers comfort, weight reduction, interior sound design... 

Primary noise control comprises measures for dealing with noise at the source suppression or modification of causes and reduction of sound emission and transmission Where such measures are inadequate for the purpose, they must be supplemented by secondary noise control, which strives to prevent or reduce sound propagation. 

LRVPs, similar to all rotary piston displacement compressors, are characterized by small vibrations and low-pulsation delivery. Nevertheless, if the operating performance does not meet the requirements of the customer, the vibration and sound emissions can be reduced by more or less extensive measures. On behalf of the most cost-effective solution possible, it requires well-founded knowledge of the procedures in the vacuum pump. 

The constancy of the vibration frequency sometimes stimulates peripheral plant components to resonant vibrations. Therewith associated sound emissions sometimes then exceed permissible limit values. 

As much as possible, one takes factory measures for reduction of vibrations and sound emissions. 

A well-engineered hydraulics and flow conveyance combined with sound-insulating materials for the employed components reduce and absorb the sound emission. Furthermore, rotating components of the LRVPs are balanced at Speck Pumpen dynamically on two levels according to DIN ISO 1940-1 with a balance quality G40. 

Increased noise emission is an indicator of a low degree of efficiency. Also, the generation of vibrations as the source of the sound emission requires an apph-cation of power. Furthermore, the components are unnecessarily stressed by the vibrations. Thus, the sound emission therefore has a direct impact on the operating costs, on the one hand, through an increased power requirement and, on the other hand, through a high service expense. 

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