The studies that I worked on in graduate school initially place in the laboratory, where it is possible to record calls under fairly controlled conditions, and thus get high-quality recordings like the one shown below.
However, this required a rather unwieldy setup, including a rack of electronic equipment that was about six feet tall
I am most interested in seeing how bats use their echolocation signals when they are flying in the wild, so I needed a system for recording and analyzing the calls bats make in the field. Using a combination of different equipment, a grant to my advisor from the NIH and a lot of work (involving several people), we assembled the following system while I was at OSU.
This system starts with a U30 bat detector from UltraSound Advice in the UK. This functions as our microphone, because it can the high-frequency sounds as an analog signal. This goes into a custom-built amplifier (designed by my advisor) that increases the amplitude of the signal by a factor of 6. This makes sure the sounds are loud enough to record accurately. This goes into a special box that has a connector that can attach to a PCMCIA card. This card plugs into the laptop and includes an analog-to-digital (A/D) converter that changes the signal into one the computer can record. The files are recorded in a program called CBDISK from Engineering Design as continuous recordings. We usually ran the recordings for about five minutes, because recording a sample rate that is high enough to record bat echolocation calls requires large files (200 MB for five minutes). These files would quickly fill up the hard drive (bearing in mind that this system was built in 2000) so we would back up recordings onto CD so that we could clear the hard drive for more recordings.