RESEARCH ON SOUND PROPAGATION IN SOUND-ABSORBENT DUCTS WITH SUPERIMPOSED AIR STREAMS. VOLUME 2

reportActive / Technical Report | Accession Number: AD0296985 | Open PDF

Abstract:

IT IS SHOWN THAT THE ATTENUATION OF SOUND IN ABSORBING DUCTS WITH SUPERIMPOSED FLOW IS DEPENDENT IN A HIGH DEGREE ON THE DIRECTION OF THE FLOW AND ITS VELOCITY. The change of attenuation is caused by a convective variation of the acoustic wavelength, by a nonlinear variation of the characteristic constants of the absorber, and by a deformation of the wave fronts in the profile of the mean flow. These changes can be calculated and are in good agreement with the experimental results. In a duct coated with undamped Helmholtz resonators the mechanism of sound amplification is based on the interaction between the sound wave and the turbulence. The conversion of kinetic flow energy into acoustic energy is performed by synchronization of turbulence. For appropriate values for flow velocity and signal frequency a long-range stable wave of pseudo-sound takes place. Sound and pseudo-sound interact with one another at the necks of the resonators.

Author(s):
Mechel, F. ; Schilz, W.
Author Organization(s):
GOETTINGEN UNIV (GERMANY F R) PHYSIKALISCHES INST
Descriptive Note:
Technical documentary rept.
Supplementary Note:
See also Volume 1, AD0296946 and Volume 3, AD0296984.
Pagination:
0085

Security Markings

DOCUMENT & CONTEXTUAL SUMMARY

Distribution:
Approved For Public Release
Distribution Statement:
Approved For Public Release; Distribution Is Unlimited.

RECORD

Collection: TR
Identifying Numbers
Report Number(s):
AMRL-TDR-62-140-VOL-2
Contract/Grant Number(s):
AF 61(052)-112
Task Number(s):
723104
Project Number(s):
7231
Monitor Series:
TDR-62-140-VOL-2, AMRL
 Subject Terms
Joint Capability Areas:
JCA_3.2_Engagement; JCA_3_Force Application; JCA_5_Command and Control; JCA_6_Net Centric; JCA_3.2.1_Kinetic Means; JCA_5.3_Planning; JCA_6.3.3_Spectrum Management; JCA_1_Force Support; JCA_1.2.7_Experimentation; JCA_6.1_Information Transport; JCA_1.3_Human Capital Management; JCA_4.5.4_Requirements Definition; JCA_4.5_Operational Contract Support; JCA_1.3.2_Personnel Management; JCA_6.3_Net Management; JCA_6.4.1_Secure Information Exchange
Modernization Areas:
Microelectronics
Communities of Interest:
Energy and Power Technologies
Descriptor(s):
*SOUND TRANSMISSION, *DUCTS, COATINGS, SOUND, ATTENUATION, ACOUSTICS, ABSORPTION, ACOUSTIC FILTERS, ACOUSTIC PROPERTIES, WEST GERMANY, ACOUSTIC IMPEDANCE, GAS FLOW, ACOUSTIC INSULATION, SCIENTIFIC RESEARCH, MEASUREMENT, THEORY
Field(s)/Group(s):
Pumps, Filters, Pipes, Tubing, Fittings and Valves, Acoustics
Keyword(s):
FOREIGN REPORTS
Report Date:
1962 Dec 01