We have proposed this idea in a project made for Prof. Zygmunt Pawłowski for the Music Academy in Warsaw. Some years ago he has made a pioneer work, measuring vibrations of the head and face of singing people, using optical holography. We have proposed to use for this purpose acoustical method and have had a success.
The method has some advantages in comparison to other methods for contactless measurement of vibrations:
1. The shape and the kind of the surface, that vibrate does not matter.
2. It is possible to measure from relatively large distance (even some meter are possible)
3. Electronics, that is necessary for this method is relatively simple and not expensive. This allows to build devices, that can measure the picture of vibration of larger surfaces, using many channels. Similar devices using laser vibrometry would be very expensive.
4. It is possible to measure exactly the amplitude of vibrations.
The sensitive of the method is now in the region of 0.1 micrometer vibration amplitude, but it can be improved.
There are also some disadvantages of this method: It is sensitive to strong movements of the air. But it seems, that it can be also improved from this point of view.
The first prototypes, that we have created some years ago was based on the measurement of phase of continuous wave. Now we have a product, that is based on pulse analysis and described here
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