A typical look of an acoustic noise specification of a sensitive metrology tool
An acoustic impulse test to estimate the sound absorption in a room
In the case of a scanning electron microscope, the majority of them have a
built-in passive or active vibration cancellation system. However that does not
exclude the susceptibility of the SEM to the induced acoustically coupled vibration.
The sources of which are usually air-handlers in a clean room. Plot A shows the
acoustic noise specification that we have created for a particular kind of scanning
electron microscope. A large speaker was used as a driving mechanism to excite the
tool at its resonant frequencies in each one third octave band. Plot B shows the
room reverberation after an impulse caused by popping of a balloon. The exponential
decay rate of the sound pressure is apparent.
