Human Speech is Bi-otic (Like Vision Can be Bi-focal)

This 'locking in' certainly exists and is generally called 'the cocktail party phenomenon'. People are able to extract 'interesting' low level messages from surrounding higher level 'noise'. It does not seem to depend much on geometrical location. Probably it is a sophisticated data processing procedure which occurs within the brain.

And it requires two ears to "focus" on the sound source that you wish to hear. I never realized this until I lost the hearing in my left ear due to an acoustic neuroma and now at "cocktail parties" or any place with higher background noise levels I cannot understand conversations at all because I cannot "focus" in on the person. When you become monaural, sometimes the background noise can become quite maddening. The other ear has virtually perfect hearing so it isn't because of a loss of sensitivity, it must have to do with how the brain can spatially locate a sound of interest and "attenuate" the rest of the background noise.

There is a silver lining. When I sleep, I put my "good" ear into the pillow and I get a great night's rest.

Most of the new hearing aids have the ability to pragmatically tune the frequency response to the needs of individual ears. My left ear is at least 20dB less sensitive than my right ear, but I purchased hearing aids for both ears for several reasons.

I can also link up wirelessly to any Blue Tooth device (i.e. cell phone) with these hearing aids, and I have 4 other defined hearing modes that I can select. I can quickly switch from normal hearing to a noise suppression mode or I can play any audio device and listen to it from up to 20 meters away - and nobody knows!!!

The geek level of these new hearing aids is pretty high, but getting them tuned up takes a little time and patience. Once you start using them, you realize how different everything seems to sound. Setting the levels and frequency response is done digitally at the office of the audiologist. But I think some analog knobs that I could tweak would be a little easier to use instead of the mouse and keyboard. I have to laugh when the doctor asks me if some particular setting sounds right. I tell her, "I don't know...I need a test environment in order to make a determination."