text: which type of a/d converter should i use for recording ultrasonic bio acoustic sounds? give me reasons please?   this is dependent on a few things, in order of importance (to me at least): 1.  how much money do you have to spend on an adc 2.  what is the input frequency range you want to capture 3.  what kind of accuracy are you looking for  as you answer those questions, start looking at how different adcs compare against what you need.  a good place to start looking is http://www.digikey.com , which sells all sorts of adcs.