Graduate School

 
 
 

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. 

 

labcall

 

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.

 
 
 

Clayton State - Recording System Mark I

 
 
 

One of the first things I did when I got to CSU was to set up a system that matched the one I used in graduate school. The computer was easy since CSU provides all faculty with laptops for teaching purposes.  The amplifier was also easy because my advisor from Ohio State built me one as a graduation present!  The rest of the stuff I cobbled together over a couple of years to produce a system that is basically the same as the one I had used previously. 


This was nice because it meant all the work developing the software and learning how things worked would carry over, which saved me a ton of time and effort!

 
 
 

Clayton State - Recording System Mark II

 
 
 

Sadly, the fact that it was fairly easy to set up that system should have been a warning that it wasn't going to last. This system depends on a PCMCIA card to connect to the microphone and convert the data to a format that can be stored on the hard drive. Sadly. PCMCIA is an obsolete technology, which means that when I upgraded my laptop I no longer had the ability to record bats! Lucky for me, the technology to record ultrasonic signals has advanced a great deal, and I was able to find a company called Dodotronic that makes a device called the UltraMic 250K, which plugs directly into the USB port and functions as a microphone that can record up to 125 kHz. This is high enough to get the calls of bats in any area where I am working, and it's a lot cheaper. I got three of these microphones for about half the cost of the Mark I system, which means I have the opportunity to use this system to record at multiple locations, which wouldn't have been possible previously. Because these work on the USB port, I have confidence that they will continue to work for a long time. The system is also potentially able to work with a tablet, so even in a post-laptop world, I should be good to go!

 
 
 
 
 
 
 
 
 
 
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