Enhancing the reproduction of multiple audio channels

1. A method of enhancing the reproduction of multiple audio channels, the channels including channels intended for playback to the front (L, R) of a listening area and a pair of channels intended for playback to the sides (Ls, Rs) of the listening area and/or a pair of channels intended for playback to the rear (Lrs, Rrs) of the listening area, comprising:

extracting two audio signals, a left vertical height signal and a right vertical height signal, from (a) the pair of channels intended for playback to the sides (Ls, Rs) of the listening area or (b) the pair of channels intended for playback to the rear sides (Lrs, Rrs) of the listening area, each of the vertical height signals comprising out-of-phase components in the pair of channels from which it is extracted, wherein said extracting extracts said out-of-phase sound information using an extractor, and

applying said left and right vertical height signals to left vertical height (Lvh) and right vertical height (Rvh) loudspeakers, the left vertical height signal being weighted to the left side and/or left rear side channel in the respective pair of channels and the right vertical height signal being weighted to the right side and/or right rear side channel in the respective pair of channels, the vertical height loudspeakers being located at the front of the listening area and above loudspeakers playing back the channels intended for playback to the front (L, R) of the listening area, one or more left vertical height loudspeakers being located above one or more loudspeakers that reproduce the left front channel and one or more right vertical height loudspeakers being located above one or more loudspeakers that reproduce the right front channel, wherein the pair of channels from which the out-of-phase sound information is extracted may be designated Ls and Rs and the extracted out-of-phase sound information may be designated Lvh and Rvh, such that the relationships among Lvh, Rvh, Ls and Rs may be characterized by

Lvh=[(0.871*Ls)−(0.49*Rs)], and

Rvh=[(−0.49*Ls)+(0.871*Rs)].

2. A method according to claim 1 wherein said extracting extracts a single-channel monophonic audio signal comprising out-of-phase components in each of said pair of channels) and divides the monophonic audio signal into two signals, a left vertical height signal and a right vertical height signal, for application, respectively, to said left vertical height (Lvh) and right vertical height (Rvh) loudspeakers.

3. A method according to claim 2 or claim 1 wherein the signals applied to said left vertical height (Lvh) and right vertical height (Rvh) loudspeakers are in phase with each other.

4. A method according to claim 1 wherein there is one pair of channels intended for playback to the sides (Ls, Rs) of the listening area, a left surround channel and a right surround channel.

5. A method according to claim 1 wherein there is one pair of channels intended for playback to the rear sides (Lrs, Rrs) of the listening area, a left rear surround channel and a right rear surround channel.

6. A method according to claim 1 wherein there are a pair of side surround channels intended for playback to the sides (Ls, Rs) of the listening area, and a pair of rear surround channels intended for playback to the rear sides (Lrs, Rrs) of the listening area, and wherein said pair of side surround channels are the left surround and right surround channels and the pair of rear surround channels are the left rear surround and right rear surround channels.

7. A method according to claim 1 wherein said extractor comprises one of a passive matrix or an active matrix.

8. A method according to claim 1 wherein said multiple audio channels are derived from a pair of audio source signals.

9. A method according to claim 8 wherein said pair of audio signals are a stereophonic pair of audio signals into which directional information is encoded.

10. A method according to claim 1 wherein said multiple audio channels are derived from more than two audio source signals comprising independent signals representing respective channels intended for playback to the front of the listening area and to the sides and/or rear of the listening area.

11. A method according to claim 10 wherein a pair of independent signals representing respective channels intended for playback to the sides and/or rear of the listening area is encoded with out-of-phase vertical height information.

12. Apparatus adapted to practice the method of claim 1 .

13. A non-transitory computer-readable storage medium encoded with a computer program for causing a computer to perform the method of any one of claim 2 or 1 .

14. A method according to claim 1 wherein said pair of channels intended for playback to the sides (Ls, Rs) of the listening area are applied to loudspeakers located at the sides (Ls, Rs) of the listening area.

15. A method according to claim 1 wherein said pair of channels intended for playback to the rear sides (Lrs, Rrs) of the listening area are applied to loudspeakers located at the rear sides (Lrs, Rrs) of the listening area.

16. A method according to claim 1 wherein said pair of channels intended for playback to the sides (Ls, Rs) of the listening area are applied to loudspeakers located at the sides (Ls, Rs) of the listening area and wherein said pair of channels intended for playback to the rear sides (Lrs, Rrs) of the listening area are applied to loudspeakers located at the rear sides (Lrs, Rrs) of the listening area.