So, as we know from the experiment with measuring the ultrasonic noise output of the quadcopter at different distances that the microphone needs to be at least 3m away from the quadcopter.
As shown from the string suspended weight this produces stability problems when the 'detector' swings about.
There seem to be a number of solutions to these problems:
What we're actually going to try:
All of them! Might as well try everything as only by experimentation are we likely to find the best option.
Firstly, we've bought a plane and will be doing the same noise test with the propeller interference. We'll also be trying wooden propellers to reduce this. The plane is a Bix3 from Hobbyking:
Secondly, we're trying to reduce the weight of the recording equipment. Instead of using a bat detector and digital recorder we'll try using this configuration:
Happily, we can use a mobile phone instead of a tablet to help keep the weight down. The microphone is an ultramic from Dodotronics.
Thirdly, we'll attempt to mount a lightweight (~100g) carbon fibre rod below the quad which will pivot with changes in pitch. This may provide problems with the roll of the quad but we'll have to see.
Finally, we will be shielding any microphone with noise insulation foam.
Hopefully through the combination of these efforts we'll have a viable vehicle to do some real world testing!