EXPERIMENTS CONCERNING THE HOLE TONE.
CALIFORNIA UNIV LOS ANGELES AEROSONICS LAB
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An experimental study was made of the discrete frequency sound generated by the impingement of an unstable circular jet on a fixed object. Two objects were used to obtain detailed information, namely, a large plate, placed normal to the jet axis, which had a hole centered on this axis and a ring with similar orientation. The former has been named the bird call, and the latter may be called the ring tone. The experimental results in the low Reynolds number range, R 5000, suggest that these systems have the same principle of operation as the edge tone, i.e., acoustic feedback. All observations reported are similar to observations made on the edge tone and are consistent with the present theory. Although the jet disturbances are symmetric in the circular systems as opposed to asymmetric in the planar, there does not appear to be any fundamental difference between them except for the type of sound field. For the hole tone it is nearly that of a monopole while for the ring tone it is closer to a dipole whose axis is oriented parallel to the jet. The edge tone has a dipole-like sound field with its axis perpendicular to the jet. The axisymmetric systems are exceedingly sensitive to out side disturbances. Author
- Fluid Mechanics