Role of Microphone sensitivity in building an SPL meter or dB meter In idea of buying an SPL meter i have drawn the specifications out in them very first and important spec is sensitivity of microphone many high priced microphones have their sensitivity arround 50mV/Pa where as some other with less cost have it arround 1V/Pa,
so what actually i want to know is, what is the actual role of Microphone sensitivity ?,for me it looks like the mic sensitivity will help in extending its dynamic range only i think..
for example the low cost meters will have differnt dB ranges

low    30-80dB, Med 50-100dB,High   80-130dB
why so

which microphones will be costly,whether a high sensitive like 12mV/Pa or a low sensitive 40mV/Pa
This is all about dynamic range since you can always compensate for sensitivity with a proper pre-amp. Dynamic range is limited at the low end by the self noise of the microphone (or the quality of the electronics) and the high end is limited by the distortion of the microphone or the clip points of the electronics.