Making low-frequency sounds audible on cheap speakers?

I hope this is the right board to post this question. I have a small library of sound effects which are being used in a game for the Nintendo 3DS. They are all 8-bit 11Mhz files. I have a problem where several of the sounds are very low-frequency effects with mostly bass sounds. These sound great through headphones, but if you try to listen to them on the 3DS speakers, you can’t hear anything at all.

Is there anything I can do to these sounds in Audacity to make them somewhat audible on the 3DS speakers? They don’t have to sound great, they just have to sound like something. Preferably I don’t want to modify the original sound heard through the headphones too much, although it’s more important that I be able to hear them both with and without headphones.

Any suggestions are greatly appreciated!

The only way that you will hear them on small speakers is to ensure that they also contain higher frequency sounds.
People often don’t realise that when they hear a double bass on TV, they often can’t hear the actual “notes” (the “fundamental frequencies”) that are being played. What they hear are the harmonics of the notes being played.

One way to add harmonics to sounds, is to apply a bit of “distortion”. Until the next version of Audacity comes out (due around the end of the year) there isn’t a dedicated distortion effect in Audacity, but there is the “Leveller” effect, which on higher settings produces distortion, so you could try that:

Wow, the leveler works great, thanks!