What is the cutoff speed-of-sound for humans to distinguish direction in water?

[Ouabache]

This wave phenomena is great!

I'm pretty sure you already know this but we humans have a natural ability to determine the direction from which a sound is emitted, and part of the ability comes from the perception of relative loudness from one ear to the other and part of it comes from an ability to sense a delay between one ear and the other. The very rapid propagation of sound underwater takes much of the delay away, and robs us of some of the perception of direction. Dolphins and whales do not have this problem.

Turbo: you're right, I am aware of this and glad that you posted your reasoning on how we perceive direction in air. Triangulation from two receiving antennas (our ears) is an efficient system that our brain handles really well.. Amazing actually

It is also a good deduction, that the rapid propagation of sound underwater is the reason why we lose direction perception. But how fast is too fast?

Is there some way we could find the cutoff speed-of-sound, beyond which we cannot distinguish direction?

Here is the information I have found so far.
In air, sound reaches one of our ears 30μsec before the other.
ref----> http://library.thinkquest.org/28170/36.html and Reshma has told us that the speed of sound in sea-water is 1531m/s . The distance between our ears (as I measure with a ruler) is approximately 7 inches (0.178m).
Also from Reshma's data, sound waves propagate 1531/343 = 4.46 times faster in the ocean than in air.