Measuring and testing – Vibration – By mechanical waves
Patent
1986-07-25
1988-09-06
Levy, Stewart J.
Measuring and testing
Vibration
By mechanical waves
73588, G01N 2904
Patent
active
047683791
ABSTRACT:
Apparatus and method for determining the steady state flow resistance of face sheets on fully assembled acoustic duct liners. Resistance is measured by subjecting the liner to a sinusoidal acoustic pressure field at the face sheet surface. The pressure field is applied through a cylindrical waveguide and is measured by a pressure transducer flush mounted on the inside of the waveguide near the liner face. A second pressure measurement, obtained by a similar transducer positioned further from the face, is combined with the first measurement to calculate the acoustic resistance for the excitation frequency. If the excitation frequency coincides with the resonant frequency of the liner configuration, then no significant pressure exists on the back surface of the liner face sheet. For this condition the root mean square (rms) pressure measured at the face sheet is equated to the static pressure drop used to obtain the steady state flow resistance. The rms velocity of the oscillating pressure wave is calculated from the ratio of the rms pressure to resistance. A repetition of the procedure for several magnitudes of dynamic pressure permits the development of a curve which describes the non-linear characteristics of resistance with changes in velocity. This curve may be equated to a similar curve obtained using steady state flow resistance measurements of the liner in its partially assembled state without a backing surface.
REFERENCES:
patent: 2981096 (1961-04-01), Carrell
patent: 3288241 (1966-11-01), Bancroft et al.
patent: 3658147 (1972-04-01), Ho et al.
patent: 3824842 (1974-07-01), Wirt et al.
patent: 3883841 (1975-05-01), Norel et al.
patent: 3960004 (1976-06-01), Wirt et al.
patent: 4249422 (1981-02-01), Gaunaurd et al.
patent: 4283953 (1981-08-01), Plona
patent: 4305295 (1981-12-01), Andersson et al.
patent: 4397187 (1983-08-01), Stribling
patent: 4403508 (1983-09-01), Langlois
patent: 4463453 (1984-07-01), Cohen et al.
patent: 4537630 (1985-08-01), Syed
Dean, "An In Situ Method of Wall Acoustic Impedance Measurement in Flow Ducts", J. of Sound & Vibration, vol. 34, No. 1, pp. 97-130, May 1974.
Blaser, D. A. and Chung, J. Y., "Transfer Function Method of Measuring In-Duct Acoustic Properties. I. Theory", J. Acoust. Soc. Am., vol. 68, No. 3, Sep. 80, pp. 907-913.
Syed, Asif A., "Acoustic Impedance Measurement System (AIMS)", Noise-Con, Jun. 1985, pp. 93-98.
Seybert, A. F. and Soenarko, Benjamin, "Error Analysis of Spectral Estimates with Application to the Measurement of Acoustic Parameters using Random Sound Fields in Ducts", J. Acoust. Soc. Am., vol. 69, No. 4, Apr. 1981, pp. 1190-1199.
Ross, D. F. and Seybert, A. F., "Experimental Determination of Acoustic Properties Using a Two-Microphone Random-Excitation Technique", J. Acoust. Soc. Am., vol. 61, No. 5, May 1977, pp. 1362-1370.
Blaser, D. A. and Chung, J. Y., "Transfer Function Method of Measuring In-Duct Acoustic Properties. II. Experiment", J. Acoust. Am., vol. 68, No. 3, Sep. 80, pp. 914-921.
Arcas Noe
Gow Joseph P.
Parente Charles A.
Aker David
Arana Louis M.
Geib Richard G.
Grumman Aerospace Corporation
Levy Stewart J.
LandOfFree
Method and apparatus for determining flow resistance of fully as does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for determining flow resistance of fully as, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for determining flow resistance of fully as will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1599874