Does any one know if the Raspberry Pi 2 is capable of playing frequencies over 40Khz from the audio jack?
The pi B and B+ get a lot of THD around 10kHz (ref).
The Hifiberry claims 192kHz (ref) but fails to show a frequency response curve.
Some Linux is not supporting anything over 192kHz (ref).
The HiFi Shield for C2/C1+ will do 50kHz (ref).
No Pi has a dedicated DAC (ref) so sound is PWMed to about 11 bit 10kHz.
So, if someone made an amplitude fall off curve for an external DAC, and you found a suitable amplifier and speakers, it might be worth a try.