About tone detection in noise with biaural hearing:
In an ancient magazine article (If I recall correctly it was "dubus") there
was a scientific reference mentioned. The signal must be delayed AND a
difference in power level feeding it to the ears. They mentioned it is
possible to get 3dB improvement with this methode.

Of course, detecting "submarine" is a good search for Google I think. They
do worn stereo head phones.

Signal detection in general is how the processing is done:
- online or offline. Offline gives the added benefit of knowing all the
signal in advance.
- bit-speed needed (Here the brain is bounded to limits)
- power level achievable (over background)
You can't beat the modern detection systems doing DSP algorithms.

- Henry