Note: This is a planned workshop on April 10th 2012 at 7:30pm.
2012 is international year of the bat: www.yearofthebat.org. Get listening to these amazing creatures with the bat detector.
The bat detector circuit converts the high frequency sounds that bats make down to the audible frequency range for us humans to hear. Typically bats send out pulses of ultrasonic frequencies in the range of 40 to 120kHz (depending upon the species of bat). Humans hearing range is in the region up to 20kHz, hence we cannot hear them. This circuit converts the ultrasonic frequensice down to human audiable level so we can hear what they are saying.
Bat detector circuit from Elektor electronics magazine November 2011. The circuit and component list can be found here
Hopefully there will be some photos put here as well.