gain?

gain is somethin i'm not able to understan in sensors. what does it mean by transmittin gain and recievin gain? and how does this help in the design of the circuitry? i'm working on ultrasonic tx and rx. and this term is confusin. data sheet mentions gain of 65 db for tx and 106 db for recieving..

It's not 'gain' it's sensitivity - db values are meaningless unless it's tells you what the reference is?.

hi,

here's the data sheet.. i think its refered as 1:mu: bar/V/meter (a small *).. what does bar mean? here's the attached datasheet...