Hi ,
I was trying to use the toneAC library to produce ultrasound in the 20kHz range. Firstly, the library works brilliantly and thank you for that 
.
The only issue that i have been having is that sound isin't loud enough. I was using a standard 4 ohm buzzer and the sound output coming from it dosnt seem to be loud enough.
I tried using an Amp LM386 circuit to amplify the output .. described here http://web.mit.edu/6.s28/www/schematics/lm386.htm
But i then had to resort to use one of the 2 pins(9 or 10) which brought the clicking soung back. I have an Atmeg168.
Any you help me figure out how can i raise the output volume. I want t be able to detect the sound in a range of abt 10 m.
Lastly, Im fairly new to this 