Soundproofing in a cylindrical duct
Abstract
A theory for soundproofing in a cylindrical duct is presented which takes the motion of a filling medium into account. The problem of sound propagation in a duct lined with a sound-absorbing material is analyzed, and approximate roots are obtained for calculating sound attenuation in a duct with impedance walls. It is shown that in the case of low acoustical conductance, the motion of the medium affects the attenuation of LF and HF sound propagating counter to the direction of that motion in the duct. It is found that the attenuation of LF sound propagating in the direction of the medium's motion is reduced in comparison with its attenuation in the presence of a nonmoving medium and that the attenuation of HF sound is increased in this case. Consideration is also given to the problem of sound propagation in a cylindrical duct having a cavity resonator at one of its walls.
- Publication:
-
In: Acousto-aerodynamic studies. (A76-10238 01-02) Moscow
- Pub Date:
- 1975
- Bibcode:
- 1975aas..book...63L
- Keywords:
-
- Acoustic Attenuation;
- Acoustic Ducts;
- Cylindrical Bodies;
- Noise Reduction;
- Absorbers (Materials);
- Acoustic Impedance;
- Aerodynamic Noise;
- Cavity Resonators;
- Sound Propagation;
- Acoustics