RESEARCH ON SOUND PROPAGATION IN SOUND-ABSORBENT DUCTS WITH SUPERIMPOSED AIR STREAMS. VOLUME 2
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1962
- Accession Number
- AD0296985
Entities
People
- F. Mechel
- W. Schilz
Organizations
- University of Göttingen