actually, there is phase information in bass that the brain does process, and it is directional information. this effect disappears above 400hz or so. try this experiment with headphones. feed 100hz into one channel, and 100.25hz into the other channel. it sounds like the source of the sound is rotating around you once every 4 seconds. do the same at any frequency below 400hz, and you can see how the brain processes phase informatio. as soon as you get above about 400 to 405hz, the effect disappears entirely. i've done this experiment, and it is a very strange experience, especially when you get to 400hz or so and the effect literally evaporates. starting at 20hz (keeping 0.25hz spacing between both channels at all times) the effect is difficult to discern, but it is there, and becomes more pronounced as you approach 400hz, then evaporates as you pass 400 hz.