I am not an electrical engineer, but I am up for a challenge and this is my first venture into electrical engineering. However I am beginning to think this may be a step to far!
As a hobby I survey insects, at the moment particularly those that 'sing' in the 6kHz to 20kHz range. Some of that range I could never hear and the rest I have mostly lost with age!
Last year I built a simple parabolic mic (an old car headlight reflector) with an Electret microphone mounted at the focal point, wired to a 3.5mm jack into my phone (Android). There I have an app, which visually displays the input from the microphone, allowing me to see the frequencies in which I am interested but can no longer hear. This didn't give me the detection range that I needed (it only gave up to about 5 metres and I'd like 10 times that or better).
So I started researching off-the-shelf kits to pre-amplify the signal and found some available online, but I need something more specific. Ideally I am only interested in amplifying a small band of frequencies from 6kHz to 20kHz. So then I started looking at active bandpass filters and have found some education material that shows calculations for the bandpass components, but I am getting a bit lost as to which amplifier to use.
Am I jumping in too deep for a complete novice? I hope that it is feasible to design/build a simple circuit powered by the Android 3.5mm jack, which will filter the frequency range in which I am interested, and amplify it to a level that doesn't damage the phone (but does increase my detection range)?
I'm assuming that the key input to the design would be the voltage from the phone jack, but what other attributes would I use to filter the choice of opamp? How do I ensure that the gain through the circuit isn't going to harm the phone?
Another input is that I'd like the resonant frequency of the bandpass amplifier to be close to 14kHz (where the hardest to detect insect 'sings').
Any pointers to appropriate references to help me progress or other considerations in the design that I have missed would be greatly appreciated.
Thanks for comments/suggestions.
The (hand)shotgun looks interesting but I think I will iterate on my parabolic mic first - a quick read suggests that the shotgun is more sensitive to be pointing accurately at the noise source whereas I will be 'scanning' with the parabolic mic as a search aid to find the source.
Should have also stated that the app I am using is actually a BAT recorder so has all the recording etc capabilities that I need (and I do use audacity to post process) but the key for this problem is detection/discovery.
Noted the advice regarding electret mics tailing off at the high end.
I think the suggestion of separation from the mobile power supply would set me off on the right tracks and give more flexibility. However, looking at an even simpler option (not being an engineer) , if I did the filtering visually in the app (as i do today) could I just use something like this: https://www.adafruit.com/product/1713 ? Is the electret frequency roll-off between 10khz to 20khz going to be significant? If so, maybe use the MAX9814 with a different mic?