Measurements on tones generated in a corrugated flow pipe with special attention to the influence of a low frequency oscillation

TL;DR

This paper investigates how low frequency oscillations in a corrugated pipe's airflow affect acoustic resonances, demonstrating that such oscillations can silence, shift, or excite pipe resonances, with implications for acoustic control.

Contribution

It provides experimental insights into the effects of low frequency oscillations on acoustic modes in corrugated pipes, highlighting their potential to modify resonance behavior.

Findings

Low frequency oscillations can silence pipe resonances.

Oscillations can shift resonances to higher harmonics.

Oscillations alone can excite higher frequency resonances.

Abstract

It is well known that an air flow in a corrugated pipe might excite the longitudinal acoustic modes of the pipe. In this letter is reported experiments where a low frequency, oscillating flow with velocity magnitudes of the same order as the air flow has been added. Depending on the oscillation strength, it might silence the pipe or move the resonances to higher harmonics. It is also shown that a low frequency oscillation by itself might excite a higher frequency acoustic resonance of the pipe.