Canceling speaker HRTFs can synthesize virtual surround sound when head position is fixed

Evidence

To convert binaural signals into a form suitable for normal stereo presentation, it is necessary to cancel out the HRTFs associated with the positions of left and right speakers, as shown in Figure 7.16. This involves using two filters that are the inverse of the HRTF to each ear and two other filters that model the cross-coupling between the two ears and subtract the effect. Clearly this is only going to be possible for a particular speaker layout and a forward-facing listener with no head movement. However, this technique is used in some proprietary spatial-enhancement systems. It has also been used in television and computer game sound reproduction to provide “virtual surround” by using the HRTFs to synthesize the surround speakers from the forward stereo ones. In this situation, not only are the speaker locations known, as they are built into the set, but the head is effectively clamped in position due to the need to watch the picture. In this sort of situation, the technique can be very effective. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2255

Categorization

• QUESTION: Does HRTF-cancellation require the listener’s head to be geometrically locked, and how do consumer systems cope with head movement?