Quasonama Four channels of audio for the 21st Century

-120° +120° right mic array +60° left mic array -60° mic -105° mic -15° mic +15° mic +105° (you) This represents the immersive panoramic soundfield as imagined, viewed from above This represents static positions of the four speakers relative to the head direction This represents virtual directions of four microphones or two stereo microphone arrays sum of right stereo image +60° sum of left stereo image -60° left inboard -15° left outboard -105° right inboard +15° right outboard +105°

We don’t need surround sound

There is little point in full 360° “surround sound”. If I heard a sudden sound behind me I’d turn around to see what it is, thus ignoring the screen! Besides, few rooms are arranged for “surround” — seating is often against a wall, leaving no rearward distance required by most “surround sound” schemes.

We have two ears, but that does not mean spatially realistic sound only needs two channels. A sonic partial panorama that “wraps around” the forward focus of attention can be more effective. Two-speaker stereo is often more deficient than assumed, while headphones can sound too separate. In real life, natural crosstalk is an important part of sonic identity.

Quasonama is panoramic sound

The aim of Quasonama is to portray a 240° partial-panoramic soundfield. This is two thirds of a circle. The left side is represented by a 120° arc, the right side by another 120° arc. The remaining 120° arc behind the listener is left to “phantom” interpretation as precise positioning there is relatively unimportant. There will be ample rearward coverage from both left and right arcs to create the impression of “behind”. Although the arcs are depicted as 120°, of course the coverage is far wider — greater than a hemisphere. When you stand adjacent to a speaker, of course you still hear it adequately!

Virtual reality audio

Quasonama will be vital for virtual reality. A VR headset may position the left and right inboard emanators a distance to the front of the ears and either side of the viewing apparatus. The outboard emanators may sit behind the earlobes (slightly outward from the head to prevent “tucking in” to neck curvature). The sensation of front to rear positional transition can rely on earlobe produced HRTF and HRIR. The difference in panning a sound from outboard to inboard across a single ear’s surroundings would cause a partial “binaural”-like effect for that ear. Combine two ears and you would have an entire immersive panorama — covering a little bit behind the left ear to a little bit behind the right ear via everything across the front of the listener.

Two modes of Quasonama

The Static mode of Quasonama assumes the room and the speakers will not move. This applies to films, movies, music and other audio reproductions of performances.

The Mobile mode assumes the sound emanators should move along with the head of the listener, such as the case of a VR headset arrangement. In these circumstances, the emanator configuration is still ±15° & ±105° but, for example, as dynamic virtual sources derived or matrixed from a full 360° soundscape.

A stereo pair of stereo pairs

Where no Quasonama speaker or headset arrangement is available, simply summing the left pair should produce a single “left” signal. Similarly, summing the right pair will produce a single “right” signal. Doing both returns us to ordinary stereo again. A Quasonama arrangement could be created from two existing satellite + subwoofer sets. The left inboard and outboard occupy one entire 2.1 speaker system (satellites become one side’s inboard and outboard with subwoofer in the middle of those) and the right inboard and outboard similarly occupy another entire 2.1 speaker system. Hence each 2.1 system is considered either totally a left set or totally a right set.

Not encoded but discrete

The advantage of Quasonama is a simpler implementation of four discrete full range unencoded channels. Conventional stereo is two discrete full range unencoded channels. By contrast, existing “surround sound” schemes are encoding schemes. The Quasonama signal is not encoded, hence the playing and amplification arrangements are a lot simpler to implement — providing there are four discrete channels available throughout the entire path from creation to delivery to consumption. In the past encoding was a consumer necessity for delivery, storage and transport of multi-channel audio. Future products should strive to include discrete four channel audio by default, easily able to be summable into conventional two channel stereo.

Inboard versus centre

The centre speaker in “surround” is commonly considered a “dialogue” channel. Influence of cinema sound schemes (rather than music) dominate sonic arrangements in the home, for those wishing to transcend two channel stereo. The two front (inboard) speakers of Quasonama are closer together than the equivalent front speakers in current “surround”. The -15° and +15° positions resemble placement either side of a fairly large screen in the home. The inboard speakers function as their own less distant virtual pair, affording more precise positioning across the screen-sized soundscape image. The inboard pair are close enough together to form a tight stereo field the size of the screen and yet avoid a “phantom centre” effect.

A partial sonic panorama

The full immersive effect comes from the left sum of the left outboard and inboard, together with the right sum of the right outboard and inboard. Overall, this produces a wider panoramic soundscape, as well as featuring a narrower front-focus soundscape. As you can imagine, from four discrete channels, we cover a partial panoramic soundscape that goes from behind one shoulder all the way round to behind the other shoulder, via a detailed front area. You would still perceive any incidental “behind you” sound distinctly enough, when present. It is preferable to consider any sound immediately behind to be an unwanted distraction, with few exception cases.

Future deployment

Games, serious games, educational material, simulations, as well as ‘ordinary’ television broadcasts and films would benefit from adopting Quasonama. Most feature films or serious television broadcasts are already sourced for “surround” encoding. Widespread acceptance of the idea of Quasonama would be helped by considering it a good idea to produce immersive content with discrete four channel audio, and to publicise the ease of implementation. Imagine if tomorrow it were natural to rely on the presence of four discrete audio channels all the way through from creation to consumption.