ACTIVE CONTROL OF NOISE TRANSMISSION THROUGH A PANEL INTO A CAVITY .2. EXPERIMENTAL-STUDY

The active control of the noise transmission through a panel into a cavity was investigated experimentally. A sound field generated by external loudspeakers was transmitted into a cavity through a simply supported panel. To control the sound transmission, an electromagnetic driver was used to adjust the panel vibration, so that the sound pressure sensed by a microphone in the cavity was minimized. Distributions of the sound pressure in the cavity and the panel vibration were measured and analyzed under controlled and uncontrolled conditions. Two different control mechanisms were identified and were associated with different types of acoustical mode. For a cavity-controlled mode, which had its resonance frequency close to an uncoupled cavity mode, the panel response increased for the controlled case even though the sound pressure in the cavity was reduced. However, for a panel-controlled mode, where the interior sound field was generated by the radiation of a resonant panel mode, the panel response was suppressed for the controlled case. These results qualitatively verify the previous analytical results [J. Pan et al., J. Acoust. Soc. Am. 87, 2098-2108 (1990)].