A particle velocity sensor to measure the sound from a structure in the presence of background noise

The performance (or quality) of a product is often checked by measuring the radiated sound (noise) from the vibrating structure. Often this test has to be done in an environment with background noise, which makes the measurement difficult. When using a (pressure) microphone the background noise can be such that it dominates the radiated sound from the vibrating structure. However, when using a particle velocity sensor, the Microflown [1,2], near the vibrating structure, the background noise has almost no influence (it is almost cancelled) and the sound from the structure is measured with a good S/N ratio. The experimental results are explained in terms of the different boundary conditions at the surface of the vibrating structure for the pressure and the particle velocity.