Structures noise generated

Cavitation, the phenomenon that causes liquids to rupture and to form vaporous/gas cavities when subjected to sufficiently low pressures, can occur in any machine handling liquid when requisite hydrodynamic conditions develop (Fig. 1). Cavitation, in many cases, is an undesirable phenomenon in hydraulic machinery that can Umit performance, lower efficiency, introduce sever structural vibration, generate acoustic noise, choke flow, and cause catastrophic damage [1]. The pernicious effects of hydrodynamic cavitation on conventional fluid machinery have been recognized and actively researched in the last century. Present knowledge (experimental and analytical) of cavitation has contributed immensely toward improving the design of conventional-scale fluid machinery. 

To quiet a noise-generating mechanism, the first impulse is often to enclose it. Enclosure can be the best solution, but not always. By determining what is causing the noise, appropriate action can be taken to be more specific and provide a cost-effective fix. A plastic enclosure can be used to suppress noise. Recognize that with a metal enclosure a small noise is transmitted to the metal structure that serves to amplify the sound. 

The structure-borne noise generation and transmission of stiffened and interconnected structures under random loads is presented. The method is based on the transfer matrix for the stuc-tural response and on the modal decomposition for the interior acoustic field. The acoustic enclosure is taken to be rectangular in shape of which portion of the boundaries are elastic while the remaining surface is acoustically rigid. Numerical results are presented for a variety of acousto-structural problems. 

A transfer matrix procedure was developed to study the noise generation and transmission for complex stiffened and interconnected structures. It has been shown that transmitted noise levels in the interior are sensitive to the structural dynamic characteristics not only of the stiffened sidewall but also of the sub-structure to which random loads are applied. Significant differences were found in noise transmission characteristics and levels between a completely coupled case and an idealized condition where the response of a sub-structure is computed independently from the response of the noise transmitting sidewall. 

R. VAICAmS and C.S. LYRINTZIS, Structure-Bome Noise Generation... 

XRD patterns in fig. 2 shows that there are 2 peaks generally at 20 = 9° and 20 = 19° which indicate the present of a-chitin and at 20 = 20° which indicate the present of chitosan. The broad peak and low intensity indicates amorphous nature of chitin-chitosan composite. As the amount of silver sulfate increases, a peak appears at 20 = 38°. The absent of peak at 38 ° for samples with lower amount of silver sulfate maybe due to the peak being covered by the noise generated due to amorphous structure of the chitin chitosan composite. 

The same effect seems to be at play in the case of the recently proposed DIFICI mechanism [112] of structure formation. There also the system is convectively unstable and the structure generated is advected away (except in the case of a loop reactor) [108]. The structures observed in the related experiments [113] in an open tubular reactor would thus be a noise generated pattern in a convectively unstable system. 

Panels for elevator walls and doors must be sufficiently light and stiff, and of a structure able to restrict noise generation and vibration during... 

Vibration and noise generated automotive structures can be reduced by a number of means, broadly classified into active, passive, and semi-active. Of special interest to this study are the passive control (i.e. absorption) methods of air-borne noise which is traditionally achieved by the use of poroelastic materials in the vehicle s dash panels, door panels, floor panels, wheelhouses, cargo bays, roof panels and upper cowl. However, the use of the traditional acoustic materials in sound absorption panels is usually accompanied by a significant increase of the overall vehicle s weight... 

Based upon a piezoelectric 1-3-composite material, air-bome ultrasonic probes for frequencies up to 2 MHz were developped. These probes are characterized by a bandwidth larger than 50 % as well as a signal-to-noise ratio higher than 100 dB. Applications are the thickness measurement of thin powder layers, the inspection of sandwich structures, the detection of surface near cracks in metals or ceramics by generation/reception of Rayleigh waves and the inspection of plates by Lamb waves. 

One important issue in medical proteomics is that of individual variations in protein expression and structure (Anderson and Anderson 2002). The protein noise that is generated by individual polymorphic variations can be significant and make the identification of specific marker proteins difficult. 

---