Acoustic engineers

The absorption coefficient values at low frequencies from 50 to 200 Hz show erratic response for all the granule sizes. One possible reason is that the superpositions of incident and reflected waves at very low frequencies create a region of maximum particle velocity. This usually occurs at V wavelength and it is common practice among acoustics engineers who design noise attenuation panels. 

Olson, H.R 1957. Acoustical Engineering. Van Nostrand Co. Reprinted. Professional Audio Journals, Philadelphia (1991). 

Honeycomb details used in a bonded acoustic engine nacelle are shown in Fig. 3. The final assembly will have solid outer skins but the inner skins will be perforated in order to reduce noise levels. 

There are, of course, limitations in the use of sound intensity meters, and there are some differences of opinion on measurement techniques. Nevertheless, the acoustic engineer s ability to measure and identify the noise from specific noise sources has been greatly enhanced. 

For the acoustics engineer, these flexible connectors are a problem because there is very little data on their acoustical performance, and the designs do not lend themselves to simple theoretical prediction. A brief laboratory investigation was carried out to compare the performances of seven types of flexible connectors with and without plates and bolsters. The tests were carried out in Altair s acoustical laboratory, which was designed to test materials using sound intensity techniques. The samples were physically quite small so the low-frequency performances were... 

This section has discussed the concepts of sound intensity, sound power, and sound pressure. It has shown how sound intensity meters have given the acoustics engineer a very powerful diagnostic tool. Noise specifications for large, complex machinery can now be checked without the need for special acoustics rooms. 

The author would like to thank Branson Ultrasonics Corporation for the opportunity to present the findings described in this paper. Also for editing assistance provided by Jeff Frantz, Director of Applications and Acoustic Engineering, Kevin Buckley, Technical Applications Manager Hot Plate and Vibration Welding, Paul Rooney, Product Manager, Laser and Spin Welding, Branson Ultrasonics Corp. 

Of course the typical seismic trace has many hundreds of reflections in it, all the way down from the surface to the deepest times measured. These days, engineers and geologists prefer to see the seismic in terms of the acoustic impedance rather than reflection data and this can be obtained by inversion from the seismic volume. Aseismic volume is made up of hundreds of thousands of traces. 

YOSHIOKA,T.- MINORU,T. Clarification of Rolling Contact Fatigue Initiation using Acoustic Emission Technique. Lubrication Engineering, Vol.51, No.l, 1995, p.41-44. 

YOSHIOKA,T. Detection of Rolling Contact Sub-Surftice Fatigue Cracks Using Acoustic Emission Technique. Lubrication Engineering, Vol.49, No.4, 1993, p.303-308. 

Koshovy V. V. Methods of restoring of the acoustical images and their applications to nondestructive testing in civil engineering // Proc. Int. Symp. Non-Destructive Testing in Civil Engineering - Berlin, Sept. 26-28, 1995. - V.2. -P. 1153-1156. 

The solution of this task results in the possibility to apply more efficient acoustic methods for investigation and diagnostics of engineering materials and weld condition. 

Up to now it was demonstrated, that the probe design enables a fast positioning and that the acoustical parameters of the probe ensure a reliable crack detection implying even a coupling control. Now, the final customer s requirement was the inspection of the blades without demounting them from the engine. 

Structure of installation enter the source-receiver of acoustic oscillations, block of ultrasonic transducers, system of scanning, control system engines, block of the analysis and registration. 

The electronic block, which includes block of the analysis and registration and control system engines, and block of the source-receiver of acoustic oscillations are universal for any installations of this type. As the source-receiver of acoustic oscillations the ultrasonic flow detector is usually use. It s, as a rule, the serial devices for example y/f2-12. The electronic block contains the microprocessor device or PC, device of the power supply and management of engines... 

Fig.6. Appearance of installation for the testing of sleeves of diesel engines. 1- ultrasonic flow detector 2- electronic blocks 3- electromechanical drives 4- acoustic transducers in a sliding bar 5- controllable detail.

Considerable attention is given in the Institute to the application of the methods of acoustic emission and optical holography for engineering diagnostics of the service life and the stressed-strained state of welded metal structures. 

H. Weltans, H. Bressler, and P. Krause, Influence of Catalytic Converters on Acoustics of Exhaust Systems forEuropean Cars, SAE 910836, Society of Automotive Engineers, Warrendale, Pa., 1991. 

Silencers are also minimally specified. Work in this area has progressed dramatically in the past few years with the NASA quiet engine program. There are some good silencers now available on the market, and inlets can be acoustically treated. 

Damewood, Glen and Nimitz, Walter, Compressor Installation Design Utilizing an Electro-Acoustical System Analog, ASME 61-WA-290, New York, NY American Society of Mechanical Engineers, 1961. 

T. Martin, Acoustic Recognition of Limited Vocabulary in Continuous Speech, Dept. Electrical Engineering, Univ, Pennsylvania, Ph.D. Thesis (1970). 

The control of acoustic resonances should always he considered in piping design. That is, acoustic resonant frequencies of piping elements should he separated from the frequencies of prominent engine harmonics as much as pos-... 

Figure 4-264. Acoustic velocity in the annulus as a function of the gas content in the mud. Courtesy Petroleum Engineer International [96].)...

The use of electrical engineering terminology here is purely for the sake of definiteness. The results obtained apply to a wide variety of problems arising in such diverse fields as mechanical vibrations, acoustics, and, with t replaced by a space parameter, optics. 

A discussion with 10 refs of combustion instability in solid-proplnt rocket engines. Two different types of instability are considered acoustic and non-acoustic instability... 

Despite the fact that thermo-acoustic instabilihes have been studied for more than a century, their control and elimination in practical combustion devices is still a problem that is difficult to master, particularly in devices with a high energy density such as aero-engines and rocket propulsion systems [24-28]. 

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