Dear Pashupati,

It seems that your requirements both combine high precision acoustics, very thin sensor and a well defined range of frequency for the pressure fluctuations.

To the best of my knowledge, for such purpose, the only solution is to use piezoelectric transducers embeded in very thin needles. I have in mind two manufacturers for such products :

https://www.acoustics.co.uk/product-category/pressure-measurement/needle-hydrophones/

http://www.gaeltec.com/products/specials-general-purpose-transducer/needle-tip-pressure-transducer-CTN/

However, you have to keep in mind that these devices only work within a specific range of frequency, which are dependent on the size of the piezo element. They are generally sold with an electronic pre-amplifier, and the overall cost can be several thousands of euros (or US dollars).

Hope this helps.