Video and Binaural Audio

I have stopped posting actively in this forum years ago, but occasionally browse here
This thread energized me to post, since I spent a considerable period of my earlier engineering employment directly engaged in binaural systems.

The ability to do an accurate localization of sound sources has particular importance for use in certain military applications, where pilots can react more quickly and reliably when their headset provide them with accurate localization of impending missles or other weapon attacks. Being able to reliably locate these threats using sound sources above, below, behind, and in front of the aircraft is of paramount importance in choosing evasive maneuvers.

In addition, binaural audio for entertainment purposes was quite popular starting in the 1970s by the release of certain commercial equipment which capitalized on this binaural effect . Bob Carver, who started several important audiophile companies including Phase Linear Corporation, Sunfire, and Carver Corporation, introduced his patented "Sonic Hologram" equipment to generate a unique variant of binaural sound fields with previously captured specially recorded vinyl disks and other media. Several competing systems were also introduced, along with a wonderful assortment of binaural recordings, many of which were released in Germany and elsewhere for sale here in the US. Some were recorded with the Aachen head, others with a similar manikin head and microphones made by Shure Corporation.

Key to the technical achievement of binaural sound are a couple very important facts which nobody in the above discussions in this thread appear to be aware of. I will include this information below for those who have a technical interest in how the binaural process actually works.

The fundamental mechanism relies on the fact that the brain can measure the so-called "Inter-Aural Time Delay" time, sometimes referred to as Ithe ITD. With the exception of sound sources which lie precisely equidistant from the left and right ear, every other sound source has a difference in arrival time between the sound arriving at one year versus the sound arriving at the opposite ear. The actual time difference is merely a result of the actual size of the human head for the individual, which notably differs from one person to another, but also differs as we age from infancy to adulthood.

In addition to this ITD which our brain learns to correlate with the angle of arrival of the sound, there is also masking and shading effects caused by the acoustic opacity of the head, making a sound coming to our left ear directly but heavily shadowed by our head when it arrives later at the other ear to hear frequency response differences. Again, our brain over tme learns to calibrate this filtering to allow us to distinguish sources in front of versus sources behind our head, along with vertical discrimination.

To make this even more interesting and complex, the fine details of our exterior ear anatomy, essentially the shape and spacing of the convolutions of the earflaps which are found on the sides of our head cause a time
filtering effect which is known as 'comb filtering' which gives us fine angle discrimination ability. These folds and hills and valleys of the outer ear are called "pinnae", and further refine our positional estimates.

There are many general articles in the audio engineering literature which document all of this anfmore, including decades of university research and corporate investment to understand and capitalize on this mechanism of human hearing which can be exploited for both entertainment as well as things like pilot workload reduction as I mentioned earlier.

I hope this lengthy but not too technical post provides some enlightenment for those who have an interest in this topic.

Larry