RESEARCH ON SOUND PROPAGATION IN SOUND-ABSORBENT DUCTS WITH SUPERIMPOSED AIR STREAMS. VOLUME 3
Abstract
Theoretical and experimental results on the interaction between sound and air flow in a duct for the following studies are presented: (1) signal amplification as related to size, shape, and position of periodically spaced Helmholtz resonators mounted in the walls of a duct; (2) extension of flow velocity and signal frequency parameters for a duct coated with a porous absorber; and (3) investigation of plate absorbers for their usefulness in wind tunnel applications. Results of these studies show, respectively: (1) the ratio of the Helmholtz resonator neck width to the spacing, for sound propagation in the flow direction, is an important factor; (2) the solution of a wave equation agrees with experimental measurements for frequencies having a wavelength greater than and comparable to the duct diameter; and 993) the attenuation is dependent of the type of plate absorber (pliable, rigid, or resilient) and the flow velocity. The construction of a test duct for determining the sound field influence on the air flow boundary layer over a plate vibrating perpendicular to its surface is also reported.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1962
- Accession Number
- AD0296984
Entities
People
- F. Mechel
- P. Mertens
- W. Schilz
Organizations
- University of Göttingen