Abstract
Vacuum-assisted toilet noise can be unsettling and even uncomfortable. One common way to reduce noise levels is to damp structural vibrations that radiate sound. We investigated whether constrained layer damping (CLD) treatments could reduce the radiated noise level on a vacuum-assisted toilet. To find the structural anti-node locations of a toilet, we excited an airplane toilet with a shaker and scanned the velocity response of the inside of the bowl with a 3-dimensional scanning laser Doppler vibrometer (3D SLDV). We also scanned the bowl with an accelerometer during a repeated flush cycle. A microphone placed one meter above the bowl measured the radiated sound level. We applied 3M 4014, 3M 2552, Pyrotek Decidamp CLD, and Velcro individually to the bowl and determined the reduction in structural vibrations and sound radiation. The bowl’s rim on the front vibrated the most. Structural vibrational energy concentrated around 100-400 Hz while radiated sound concentrated around 400 Hz–2 kHz. Applying damping materials reduced structural vibrations, sometimes by 20 dB. We conclude that CLD treatments are able to reduce structural vibrations. Further results of the investigation will be shown and discussed.
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