Method for controlling a three-dimensional multi-layer speaker arrangement and apparatus for playing back three-dimensional sound in an audience area

Abstract

A method for controlling a three-dimensional multi-layer speaker arrangement having a plurality of speakers arranged in spaced layers. The method includes: providing information for a sound to be played back from a 3D source position assigned to the sound, wherein the source position is defined with respect to a reference point (RP) within the multi-layer speaker arrangement, extracting a 2D source position (SPXY) from the source position and calculating layer specific speaker coefficients using a 2D calculator to position the sound two dimensional source position, and feeding a vertical pan or 3D source position into a multilayer calculator for obtaining a layer gain factor for each layer for obtaining speaker coefficients used as individual gains enabling the speakers to play back the sound.

Claims

1. A method for controlling a three-dimensional multi-layer speaker arrangement comprising a plurality of speakers arranged in a number of speaker layers (L.sub.0, L.sub.1, L.sub.1) spaced from each other, the method comprising: providing a sound information for a sound to be played back from a three dimensional source position (PS) assigned to the sound, wherein the source position (PS) is defined with respect to a reference point (RP) within the multi-layer speaker arrangement; extracting a two-dimensional source position (SP.sub.xy) from the source position (SP) and calculating layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) using a two-dimensional calculator in order to position the sound at the two-dimensional source position (SP.sub.XY); feeding a vertical pan (n.sub.L) or the three dimensional source position (SP) into a multilayer calculator for obtaining a layer gain factor (g.sub.L0, g.sub.L1, g.sub.L1) for each layer (L.sub.0, L.sub.1, L.sub.1), and multiplying the layer gain factors (g.sub.L0, g.sub.L1, g.sub.L1) with the respective layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for obtaining speaker coefficients (SC.sub.L1, SC.sub.L1, SC.sub.L0)used as individual gains for the speakers for playing back the sound, wherein at least one of the speaker layers (L.sub.1, L.sub.1, L.sub.0) comprises a speaker segment being an arrangement of speakers covering only a limited opening angle (.sub.o) from the perspective of the reference point (RP) projected into the respective speaker layer (L.sub.1, L.sub.1, L.sub.0), wherein the multilayer calculator comprises a step (S6), in which a final vertical pan (n.sub.Lf) is set to a neighbouring speaker layer (L.sub.1, L.sub.1, L.sub.0) having a speaker polygon if the source position (SP) is outside the opening angle (.sub.O) and outside an adjacent blend angle (.sub.B) defined as the angle between the opening angle (.sub.O) and the first speaker outside this opening angle (.sub.O) in the neighbouring speaker layer (L.sub.1, L.sub.1, L.sub.0), wherein the final vertical pan (n.sub.Lf) is blended between the layer (L.sub.1, L.sub.1, L.sub.0) with the speaker segment and the neighbouring speaker layer (L.sub.1, L.sub.1, L.sub.0) having the speaker polygon if the source position (SP) is within the blend angle (.sub.B), and wherein step (S6) is skipped if the source position (SP) is within the opening angle (.sub.O).

2. The method according to claim 1, wherein the speakers within at least one of the speaker layers (L.sub.0, L.sub.1, L.sub.1) are arranged as a speaker polygon.

3. The method according to claim 1, wherein the two-dimensional calculator determines the layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for the individual speakers taking into account a geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, S.sub.L0)).

4. The method according to claim 3, wherein the multilayer calculator determines the layer gain factors (g.sub.L1, g.sub.L1, g.sub.L0) taking into account the geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0)) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.0) and the position of the speaker layers (L.sub.1, L.sub.1, L.sub.0) relative to each other and to the reference point (RP).

5. The method according to claim 3, wherein the multilayer calculator comprises a step (S5), in which the three dimensional source position (SP) is used to calculate the vertical pan (n.sub.L) of the sound source taking into account the geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.0) and the position of the speaker layers (L.sub.1, L.sub.1, L.sub.0) relative to each other and to the reference point (RP).

6. A method for controlling a three-dimensional multi-layer speaker arrangement comprising a plurality of speakers arranged in a number of speaker layers (L.sub.0, L.sub.1, L.sub.1) spaced from each other, the method comprising: providing a sound information for a sound to be played back from a three dimensional source position (PS) assigned to the sound, wherein the source position (PS) is defined with respect to a reference point (RP) within the multi-layer speaker arrangement; extracting a two-dimensional source position (SP.sub.xy) from the source position (SP) and calculating layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) using a two-dimensional calculator in order to position the sound at the two-dimensional source position (SP.sub.xy ); feeding a vertical pan (n.sub.L) or the three dimensional source position (SP) into a multilayer calculator for obtaining a layer gain factor (g.sub.L0, g.sub.L1, g.sub.L1) for each layer (L.sub.0, L.sub.1, L.sub.1); and multiplying the layer gain factors (g.sub.L0, g.sub.L1, g.sub.L1) with the respective layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for obtaining speaker coefficients (SC.sub.L1, SC.sub.L1, SC.sub.L0) used as individual gains for the speakers for playing back the sound, wherein the speaker layers (L.sub.0, L.sub.1, L.sub.1) are arranged in parallel to each other and to an audience area (A), wherein the layer (L.sub.0) which is nearest to the level of the audience area (A) is assigned a layer number (N.sub.L) with the value 0, wherein layers (L.sub.1) above this layer (L.sub.0) are assigned increasing positive integer layer numbers (N.sub.L) and layers (L.sub.1) beneath this layer (L.sub.0) are assigned decreasing negative integer layer numbers (N.sub.L), wherein the layer gain factor (g.sub.L) for a layer (L.sub.0, L.sub.1, L.sub.1) is calculated by subtracting the absolute value of the difference of the vertical pan (n.sub.L) and the layer number (N.sub.L) from 1 if the absolute value of the difference of the vertical pan (n.sub.L) and the layer number (N.sub.L) is at most 1, and wherein the layer gain factor (g.sub.L) is set to 0 otherwise.

7. The method according to claim 6, wherein the reference point (RP) is inside the audience area (A).

8. The method according to claim 6, wherein the speakers within at least one of the speaker layers (L.sub.0, L.sub.1, L.sub.1) are arranged as a speaker polygon.

9. The method according to claim 6, wherein the two-dimensional calculator determines the layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for the individual speakers taking into account a geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (S.sub.1, S.sub.1, S.sub.L0).

10. The method according to claim 9, wherein the multilayer calculator determines the layer gain factors (g.sub.L1,g.sub.L1, g.sub.L0) taking into account the geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.0) and the position of the speaker layers (L.sub.1, L.sub.1, L.sub.0) relative to each other and to the reference point (RP).

11. The method according to claim 9, wherein the multilayer calculator comprises a step (S5), in which the three dimensional source position (SP) is used to calculate the vertical pan (n.sub.L) of the sound source taking into account the geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.0) and the position of the speaker layers (L.sub.1, L.sub.1, L.sub.0) relative to each other and to the reference point (RP).

12. A method for controlling a three-dimensional multi-layer speaker arrangement comprising a plurality of speakers arranged in a number of speaker layers (L.sub.0, L.sub.1, L.sub.1) spaced from each other, the method comprising: providing a sound information for a sound to be played back from a three dimensional source position (PS) assigned to the sound, wherein the source position (PS) is defined with respect to a reference point (RP) within the multi-layer speaker arrangement; extracting a two-dimensional source position (SP.sub.xy) from the source position (SP) and calculating layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) using a two-dimensional calculator in order to position the sound at the two-dimensional source position (SP.sub.xy ); feeding a vertical pan (n.sub.L) or the three dimensional source position (SP) into a multilayer calculator for obtaining a layer gain factor (g.sub.L0, g.sub.L1, g.sub.L1) for each layer (L.sub.0, L.sub.1, L.sub.1); and multiplying the layer gain factors (g.sub.L0, g.sub.L1, g.sub.L1) with the respective layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for obtaining speaker coefficients (SC.sub.L1, SC.sub.L1, SC.sub.L0) used as individual gains for the speakers for playing back the sound, wherein the multilayer calculator comprises a step (S7) with a layer gains mapper for calculating the layer gain factors (g.sub.L1,g.sub.L1, g.sub.L0), wherein a pair of neighbouring layers with a lower layer (N.sub.LL) below and an upper layer (N.sub.LU) above the source position (SP) is selected, wherein the speakers within at least one of the speaker layers (L.sub.0, L.sub.1, L.sub.1) are arranged as a speaker polygon, wherein the vertical pan (n.sub.L) is rounded if the source is positioned inside one of the speaker polygons, wherein a level ratio (r) is calculated by the equation $r = \frac{n - N_{LL}}{N_{LU} - N_{LL}},$ wherein the layer gains (g.sub.l, g.sub.u) of the lower layer (N.sub.LL) and the upper layer (N.sub.LU) are calculated by the equations g.sub.u=r and g.sub.l=1r, and wherein the layer gains (g.sub.1, g.sub.u) are normalized by their power sum.

13. The method according to claim 12, wherein the two-dimensional calculator determines the layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for the individual speakers taking into account a geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.L0).

14. The method according to claim 13, wherein the multilayer calculator determines the layer gain factors (g.sub.L1,g.sub.L1, g.sub.L0) taking into account the geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.0) and the position of the speaker layers (L.sub.1, L.sub.1, L.sub.0) relative to each other and to the reference point (RP).

15. The method according to claim 13, wherein the multilayer calculator comprises a step (S5), in which the three dimensional source position (SP) is used to calculate the vertical pan (n.sub.L) of the sound source taking into account the geometrical speaker setup (S.sub.L1, S.sub.L1, S.sub.L0) in the respective speaker layer (L.sub.1, L.sub.1, L.sub.0) and the position of the speaker layers (L.sub.1, L.sub.1, L.sub.0) relative to each other and to the reference point (RP).

16. The method according to claim 15, wherein in step (S5) an auxiliary 2D plane is fit through the reference point (RP) and the source position (SP) such that the auxiliary 2D plane cuts an audience area (A) at right angles, wherein the two positions, where the auxiliary 2D plane cuts the boundaries of the speaker layers (L.sub.1, L.sub.1) are defined as panning intersection points (PIP.sub.L1, PIP.sub.L1), wherein elevation direction vectors (EDV.sub.L1 EDV.sub.L1) for the respective speaker layer (L.sub.1, L.sub.1) are constructed between the reference point (RP) and the panning intersection points (PIP.sub.L1, PIP.sub.L1), wherein a source vector (SV) is constructed between the reference point (RP) and the source position (SP), wherein the elevation direction vectors (EDV.sub.L1 EDV.sub.L1) and the source vector (SV) are fed into a 2D calculator for calculating the layer gain factors (g.sub.L1,g.sub.L1).

17. The method according to claim 15, wherein the two dimensional panning algorithm in step (S5) comprises Vector Base Amplitude Panning.

18. An apparatus for playing back three-dimensional sound in an audience area (A), comprising: a three-dimensional multi-layer speaker arrangement comprising a plurality of speakers arranged in a number of speaker layers (L.sub.0, L.sub.1, L.sub.1) spaced from each other; and a control unit for multi-layer speaker arrangement, wherein the control unit is arranged to perform: providing a sound information for a sound to be played back from a three dimensional source position (PS) assigned to the sound, wherein the source position (PS) is defined with respect to a reference point (RP) within the multi-layer speaker arrangement; extracting a two-dimensional source position (SP.sub.xy) from the source position (SP) and calculating layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) using a two-dimensional calculator in order to position the sound at the two-dimensional source position (SP.sub.xy); feeding a vertical pan (n.sub.L) or the three dimensional source position (SP) into a multilayer calculator for obtaining a layer gain factor (g.sub.L0, g.sub.L1, g.sub.L1) for each layer (L.sub.0, L.sub.1, L.sub.1); and multiplying the layer gain factors (g.sub.L0, g.sub.L1, g.sub.L1) with the respective layer specific speaker coefficients (SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D, SC.sub.L0.sub._.sub.2D) for obtaining speaker coefficients (SC.sub.L1, SC.sub.L1, SC.sub.L0) used as individual gains for the speakers for playing back the sound, wherein at least one of the speaker layers (L.sub.1, L.sub.1, L.sub.0) comprises a speaker segment being an arrangement of speakers covering only a limited opening angle (.sub.O) from the perspective of the reference point (RP) projected into the respective speaker layer (L.sub.1, L.sub.1, L.sub.0), wherein the multilayer calculator comprises a step (S6), in which a final vertical pan (n.sub.Lf) is set to a neighbouring speaker layer (L.sub.1, L.sub.1, L.sub.0) having a speaker polygon if the source position (SP) is outside the opening angle (.sub.O) and outside an adjacent blend angle (.sub.B) defined as the angle between the opening angle (.sub.O) and the first speaker outside this opening angle (.sub.O) in the neighbouring speaker layer (L.sub.1, L.sub.1, L.sub.0), wherein the final vertical pan (n.sub.Lf) is blended between the layer (L.sub.1, L.sub.1, L.sub.0) with the speaker segment and the neighbouring speaker layer (L.sub.1, L.sub.1, L.sub.0) having the speaker polygon if the source position (SP) is within the blend angle (.sub.B), wherein step (S6) is skipped if the source position (SP) is within the opening angle (.sub.O).

Description

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is a schematic view of a three dimensional multi-layer speaker arrangement with two speaker layers in a three dimensional space,

(3) FIG. 2 is a schematic block diagram of a first embodiment of a method for controlling the multi-layer speaker arrangement,

(4) FIG. 3 is a schematic block diagram of a second embodiment of a method for controlling the multi-layer speaker arrangement,

(5) FIG. 4 is a schematic block diagram of the multilayer calculator,

(6) FIG. 5 is a perspective view of a 3D multilayer speaker arrangement,

(7) FIG. 6 is a top view of the 3D multilayer speaker arrangement,

(8) FIG. 7 is another top view of the 3D multilayer speaker arrangement,

(9) FIG. 8 illustrates a 2D vector base gain factor calculation, and

(10) FIG. 9 illustrates the selection of the layer id part addressing a pair of neighbouring layers.

(11) Corresponding parts are marked with the same reference symbols in all figures.

(12) FIG. 1 is a schematic view of a three dimensional multi-layer speaker arrangement 1 with two speaker layers L.sub.1 and L.sub.1 in a three dimensional space such as a room or a cinema. The speaker layer L.sub.1 is arranged above an audience area A and therefore referred to as an upper layer L.sub.1 with a layer number N.sub.L=1. The speaker layer L.sub.1 is arranged below the audience area A and therefore referred to as a lower layer L.sub.1 with a layer number N.sub.L=1.

(13) A sound is intended to be played back such that it appears to originate from a pre-determined point or position in the room referred to as a source position SP. The source position SP is defined with respect to a coordinate system having its reference point RP in the centre of the audience area A. The audience area A is considered a horizontal plane extending in the directions X and Y and having a height Z with the value 0. All points in the audience area A have an elevation angle with the value 0. The upper speaker layer L.sub.1 is arranged as a speaker polygon in parallel above the audience area at a height Z.sub.1. The lower speaker layer L.sub.1 is arranged as a lower speaker polygon in parallel beneath the audience area at a height Z.sub.1. In the embodiment illustrated the source position SP is located between the audience area A and the upper speaker layer L.sub.1.

(14) The boundaries of the speaker layers L.sub.1 and L.sub.1 are defined by a speaker polygon formed by arranging a number of speakers 2 in the respective speaker layer L.sub.1 and L.sub.1, wherein at least a subset of the speakers 2 are the vertices or corners of the polygon. In the illustrated embodiment the upper speaker layer L.sub.1 is a rectangle while the lower speaker layer L.sub.1 is a trapezoid covering a smaller area than the upper speaker layer L.sub.1. The illustrated shapes are given by way of example only. In alternative embodiments the speaker layers L.sub.1, L.sub.1 may have different shapes.

(15) In alternative embodiments the multi-layer speaker arrangement 1 may comprise more than two speaker layers L.sub.1, L.sub.1 In particular it may comprise an additional speaker layer at the level of the audience area A.

(16) FIG. 2 is a schematic block diagram of a first embodiment of a method for controlling the multi-layer speaker arrangement such that the sound appears to be played back from the pre-determined source position SP.

(17) In the first embodiment the pre-determined source position SP is provided by a memory medium. In the memory medium, individual sounds or sound sequences are assigned to absolute three dimensional source positions SP or three dimensional source trajectories, i.e. sequences of source positions SP. Each three dimensional source position SP may be defined by Cartesian and/or spherical coordinates with respect to the reference point RP. For example, the source position SP may be defined by three values in the directions X, Y and Z. In another example, the three-dimensional source position SP may be defined by two Cartesian coordinates in the XY plane, i.e. the audience area A and a source elevation angle above the audience area A. Likewise the three-dimensional source position SP may be defined by spherical coordinates comprising a radius, i.e. a distance between the source and the reference point RP, further comprising a source azimuth angle and a source elevation angle above the audience area A.

(18) In a step S1 of the method the sound source is projected into the two-dimensional XY plane, i.e. a source height value SP.sub.Z in the direction Z is removed from the source position SP. In the embodiment illustrated in FIG. 1 the projected source position SP.sub.XY is inside the upper speaker layer L.sub.1 but outside the lower speaker layer L.sub.1. In steps S2.1, S2.2 the projected two dimensional source position SP.sub.XY is fed into respective 2D calculators for the speaker layers L.sub.1, L.sub.1. Taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 the 2D calculator determines layer specific speaker coefficients SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D for the individual speakers 2 within the speaker layer L.sub.1, L.sub.1 in order to virtually play the sound back from the respective projected two dimensional source position SP.sub.XY. In a step S3 the source position SP is fed into a multilayer calculator whose details are illustrated in FIG. 4. Taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 and the position of the speaker layers L.sub.1, L.sub.1 relative to each other and to the reference point RP the multilayer calculator determines layer gain factors g.sub.L1, g.sub.L1 for each speaker layer L.sub.1, L.sub.1. In steps S4.1, S4.2 the layer specific speaker coefficients SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D are multiplied by the respective gain factors g.sub.L1, g.sub.L1resulting in speaker coefficients SC.sub.L1, SC.sub.L1, i.e. the individual gain used for each speaker 2 in order to make the sound source appear to be played back from the source position SP.

(19) The method illustrated in FIG. 2 may be expanded to more than two speaker layers L.sub.1, L.sub.1 by adding respective branches in parallel to the branches consisting of the steps S2.1, S4.1 and S2.2, S4.2. For example a branch with steps S2.3 and S4.3 for a speaker layer L.sub.0 with a speaker polygon arranged at the level of the audience area A may be additionally provided.

(20) FIG. 3 is a schematic block diagram of a second embodiment of a method for controlling the multi-layer speaker arrangement 1 such that the sound appears to be played back from the pre-determined source position SP.

(21) As in the first embodiment the pre-determined source position SP is provided by a memory medium. In the memory medium, individual sounds or sound sequences are assigned to relative three dimensional source positions SP or relative three dimensional source trajectories, i.e. sequences of source positions SP. Each source position SP is defined by two-dimensional Cartesian and/or polar coordinates with respect to the reference point RP within the XY-plane. A relative position of the source in the Z direction is referred to as the vertical pan n.sub.L, which relates to the speaker layer numbers N.sub.L. For example, a vertical pan n.sub.L of 0.8 would represent a relative height of the source at 80% of the height of the speaker layer L.sub.1 above the audience area A or the layer L.sub.0, respectively. The vertical position of the source in this embodiment therefore depends on the actual speaker setup S.sub.L1, S.sub.L1, S.sub.L0 of the speaker layers L.sub.1, L.sub.1, L.sub.0.

(22) In steps S2.1, S2.2 the two dimensional source position SP.sub.XY is fed into respective 2D calculators for the speaker layers L.sub.1, L.sub.1. Taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 the 2D calculator determines layer specific speaker coefficients SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D for the individual speakers 2 within the speaker layer L.sub.1, L.sub.1 in order to virtually play the sound back from the respective projected two dimensional source position SP.sub.XY. In a step S3 the vertical pan n.sub.L of the source position SP is fed into a multilayer calculator whose details are illustrated in FIG. 4. Taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 the multilayer calculator determines layer gain factors g.sub.L1, g.sub.L1 for each speaker layer L.sub.1, L.sub.1. In steps S4.1, S4.2 the layer specific speaker coefficients SC.sub.L1.sub._.sub.2D, SC.sub.L1.sub._.sub.2D are multiplied by the respective layer gain factors g.sub.L1, g.sub.L1 resulting in speaker coefficients SC.sub.L1, SC.sub.L1, i.e. the individual gain used for each speaker 2 in order to make the sound source appear to be played back from the source position SP.

(23) The method illustrated in FIG. 3 may be expanded to more than two speaker layers L.sub.1, L.sub.1 by adding respective branches in parallel to the branches consisting of the steps S2.1, S4.1 and S2.2, S4.2. For example a branch with steps S2.3 and S4.3 for a speaker layer L.sub.0 with a speaker polygon arranged at the level of the audience area A may be additionally provided.

(24) FIG. 4 is a schematic block diagram of the multilayer calculator used in step S3 of the methods according to FIGS. 2 and 3.

(25) If the multilayer calculator is called from the method according to the first embodiment (cf. FIG. 2) it is fed the three dimensional source position SP. Taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 and the position of the speaker layers L.sub.1, L.sub.1 relative to each other and to the reference point RP in a step S5 the three dimensional source position SP is used to calculate the vertical pan n.sub.L of the sound source.

(26) In step S5 the layer elevation angle .sub.L1, .sub.L1 for every speaker layer L.sub.1, L.sub.1 in relation to the source elevation angle is calculated. These layer elevation angles .sub.L1, .sub.L1 depend on the source position SP. Based on the differences between these layers elevation angles .sub.L1, .sub.L1 and the source elevation angle which all are lined up in a 2D plane the layer gain factors g.sub.L1, g.sub.L1 can be calculated by using an algorithm similar to a 2D panning algorithm, e.g. VBAP.

(27) The layer gain factors g.sub.L0, g.sub.L1, g.sub.L1 are a function of the respective layer elevation angles .sub.L1, .sub.L1, .sub.L1 or a function of the angles and , wherein is the difference angle between .sub.L1 and and wherein is the difference angle between .sub.L1 and . Vectors i, j and k are unit length vectors representing the elevation of the lower speaker layer L.sub.1, the upper speaker layer L.sub.1 and the source position SP. By using the angles and to construct the vectors i, j and k in the 2D plane, a vector based approach similar to VBAP 2D can be used to calculate the layer gain factors or alternatively the ratio part of the vertical pan value as detailed below.

(28) FIG. 8 illustrates the 2D vector base gain factor calculation. The two unit length vectors i and j form a vector base and the unit length vector k of the source can be expressed as linear combination of vectors i and j. The layer gain factors g.sub.L0 and g.sub.L1 of two exemplary neighbouring layers L.sub.0, L.sub.1 are obtained by the equation (1):
k=g.sub.L0i+g.sub.L1j(1)

(29) The equation may likewise be performed for other pairs of neighbouring layers. For additional operations it is advantageous to have one value expressing the ratio r between the two layer gain factors g.sub.L0, g.sub.L1. The ratio r is the fractional part of the vertical pan. The relation between the ratio r and the layer gain factors g.sub.L0, g.sub.L1 is shown in equations (3), (4), (5) and (6).

(30) $\begin{matrix} g_{L 0} = 1 - r & (3) \\ g_{L 1} = r & (4) \\ r = \frac{g_{L 1}}{g_{L 0} + g_{L 1}} & (5) \\ 1 - r = \frac{g_{L 0}}{g_{L 0} + g_{L 1}} & (6) \end{matrix}$

(31) When using more than two speaker layers, an integer value, which addresses a pair of neighbouring layers, may be used in addition to the gain ratio r. For this purpose the layers are assigned consecutive numbers. For the vertical pan the layer address and the ratio r can be expressed by one real number whose integer part is the layer number N.sub.L and whose fractional part is the gain ratio r. This kind of representation leads to the vertical pan value described in the following.

(32) The layer number N.sub.L part of the vertical pan value is determined by finding the 2D transformed layer pair vectors which enclose the source vector SV.

(33) FIG. 9 illustrates the selection of the layer id part addressing a pair of neighbouring layers. In this example, the source vector SV is located between the elevation direction vectors EDV.sub.L0 and EDV.sub.L1. Hence, the layer pair L.sub.0 and L.sub.1 will be selected. The resulting integer part of the vertical pan value will therefore be 0.

(34) FIG. 1 shows the construction of the layer elevation angles .sub.L1, .sub.L1 in detail. An auxiliary 2D plane is fit through the reference point RP and the source position SP such that the auxiliary 2D plane cuts the audience area A at right angles. The two positions, where the auxiliary 2D plane cuts the boundaries of the envelop polygons of the upper speaker layer L.sub.1 and the lower speaker layer L.sub.1 are defined as panning intersection points PIP.sub.L1, PIP.sub.L1. This intersection operation may be calculated in the 2D space of the layer. The 2D panning intersection point PIP.sub.L1, PIP.sub.L1 may then be transformed back to 3D.

(35) A respective line from the reference point RP to the panning intersection point PIP.sub.L1, PIP.sub.L1 is referred to as the elevation direction vector EDV.sub.L1 EDV.sub.L1 for the respective speaker layer L.sub.1, L.sub.1. A line from the reference point RP to the source position SP is referred to as the source vector SV. All elevation direction vectors EDV.sub.L1 EDV.sub.L1 and the source vector SV are coplanar within the auxiliary 2D plane. The elevation direction vectors EDV.sub.L1 EDV.sub.L1 and the source vector SV can be transformed to 2D within the auxiliary 2D plane and then be fed into a 2D calculator which returns the layer gain factors g.sub.L1, g.sub.L1 to be used in the method in order to properly localize the 3D source. The 2D calculator may for example be a VBAP calculator as disclosed in V. Pulkki, Virtual Sound Source Positioning Using Vector Base Amplitude Panning, J. Audio Eng. Soc., Vol. 45, pp. 456-466, No. 6, 1997 Jun. In another embodiment the 2D calculator may be a WFS calculator.

(36) If the multilayer calculator is called from the method according to the second embodiment (cf. FIG. 3) step S5 is skipped as the vertical pan n.sub.L of the sound source is provided in the first place.

(37) Step S6 is an optional step which is performed in case one of the speaker layers L.sub.1, L.sub.1, L.sub.0 comprises a speaker segment instead of a speaker polygon, a speaker segment being an arrangement of speakers 2 covering only a limited angle when seen from the reference point or from the Z axis of the coordinate system. In the step S6 taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 and the position of the speaker layers L.sub.1, L.sub.1 relative to each other and to the reference point RP the vertical pan n.sub.L is manipulated so as to determine a final vertical pan n.sub.Lf. Conventional multilayer speaker arrangements 1 typically have an array or speaker segment of lower front speakers 2 at the bottom of a cinema screen. These speakers 2 define a lower layer L.sub.1 in the multilayer arrangement 1 with a non closed speaker polygon or ring which may be referred to as the speaker segment. The solution for such a situation is to use the speakers 2 of a neighbouring layer L.sub.0 which has speakers 2 in the non covered angle range. Depending on the source azimuth angle the given vertical pan n.sub.L is manipulated to blend to the fully equipped neighbouring layer L.sub.0 thereby obtaining the final vertical pan n.sub.Lf. Blend angles .sub.B are defined as the angle between a lower speaker segment opening angle .sub.O, i.e. an angle between two vectors obtained by connecting the reference point RP with the outermost speakers 2 of the speaker segment, and the first speaker outside of this opening angle in the neighbouring speaker layer L.sub.0 (cf. FIG. 7).

(38) If all speaker layers L.sub.1, L.sub.1, L.sub.0 comprise complete speaker polygons step S6 is skipped and the vertical pan n.sub.L is used as the final vertical pan n.sub.Lf.

(39) In a step S7 taking into account the geometrical speaker setup S.sub.L1, S.sub.L1 in the respective speaker layer L.sub.1, L.sub.1 and the position of the speaker layers L.sub.1, L.sub.1 relative to each other and to the reference point RP the final vertical pan n.sub.Lf is fed into a layer gains mapper.

(40) The vertical pan n.sub.L or final vertical pan n.sub.Lf directly maps to the layer gain factors g.sub.L1, g.sub.L1. For this, every speaker layer L.sub.1, L.sub.1, e.g. every speaker polygon has a layer number N.sub.L assigned. When creating the speaker setup, the speaker layers are assigned layer numbers N.sub.L. A main layer L.sub.0, which is typically the nearest layer to the ear level, i.e. the audience area A, has number 0, layers above have positive numbers (1,2, . . . ), lower layers have negative numbers (1,2, . . . ).

(41) In the cinema case speakers near ear level may be assigned the layer number N.sub.L=0, speakers above a screen or on a ceiling are assigned the layer number N.sub.L=1 and speakers below ear level, e.g. at the lower edge of the screen are assigned layer number N.sub.L=1.

(42) In cases with speakers above and below ear level only, no speakers are assigned layer number N.sub.L=0.

(43) Sources are assigned 2D coordinates SP.sub.XY and a vertical pan or blend value n.sub.L. Sources outside of all speaker envelop polygons can be panned to every layer L.sub.1, L.sub.1, L.sub.0 and between them. For sources inside at least one of the speaker envelop polygons the vertical pan value is rounded to an integer value so that there is no blending but only switching between the layers L.sub.1, L.sub.1, L.sub.0 because blending between layers L.sub.1, L.sub.1, L.sub.0 may produce unpleasant sound if one of the layers L.sub.1, L.sub.1, L.sub.0 renders a focussed source (Source position inside a layer envelope polygon means focussing if the layer algorithm is WFS).

(44) Before calculating the layer gain factors the vertical pan value n is rounded if the source is inside one of the layer envelope polygons:
n=round(n)(7)

(45) Then a pair of neighbouring speaker layers L.sub.1, L.sub.0, L.sub.1 with one layer above and one layer below the source position SP is determined. The selected layer numbers N.sub.L may be referred to as N.sub.LU and N.sub.LL.

(46) For example there are three layers L.sub.1, L.sub.0, L.sub.1. The vertical pan value n.sub.L of the source is 0.3. Hence, the layer L.sub.0 is the lower layer with layer number N.sub.LL and the layer L.sub.1 is the upper layer with layer number N.sub.LU. The layers N.sub.LU and N.sub.LL will be used for playing back the sound of the source.

(47) In order to determine the layer gain factors g.sub.u, g.sub.L of the layers N.sub.LU and N.sub.LL a layer ratio r is is calculated:

(48) $\begin{matrix} r = \frac{n - N_{LL}}{N_{LU} - N_{LL}} & (8) \end{matrix}$

(49) With the ratio r the gains g.sub.u, g.sub.l are calculated as follows:
g.sub.u=r(9)
g.sub.l=1r(10)

(50) To keep the perceived loudness constant the gains g.sub.u, g.sub.l are normalized by their power sum:

(51) $\begin{matrix} g_{u_norm} = \frac{g_{u}}{\sqrt{g_{u}^{2} + g_{l}^{2}}} & (11) \\ g_{l_norm} = \frac{g_{l}}{\sqrt{g_{u}^{2} + g_{l}^{2}}} & (12) \end{matrix}$

(52) The method for controlling the multi-layer speaker arrangement 1 fits well for speaker arrangements 1 where every layer is a complete polygon or ring of speakers 2. In this context, ring means that an angle between neighbouring speakers 2 is not larger than 120 degrees. In practice, there exist speaker arrangements 1 which don't meet this condition. For example one of the speaker layers L.sub.1, L.sub.1, L.sub.0 may comprise a speaker segment instead of a speaker polygon, a speaker segment being an arrangement of speakers 2 covering only a limited angle when seen from the reference point or from the Z axis of the coordinate system. In this case step S6 would be performed as described above.

(53) FIGS. 5, 6 and 7 show a typical 3D multilayer speaker arrangement 1 as for example used in a cinema. The 3D multilayer speaker arrangement 1 comprises three layers L.sub.0, L.sub.1, L.sub.1, the main speaker polygon L.sub.0 with layer number N.sub.L=0 at ear level in the audience area A, ceiling speakers 2 in a laminar, grid-like arrangement in speaker layer L.sub.1 and a lower front speaker segment forming the layer L.sub.1. The laminar, grid-like arrangement of speaker layer L.sub.1 can be approximated so that it can be handled as a layer. In the approximation the z-components of the speaker coordinates are ignored, i.e. projected into an xy-plane along the z-axis, so that the resulting 2D speaker grid can then be controlled by a suitable 2D laminar panning algorithm, e.g. by triangulating the 2D grid (delaunay triangulation) and then panning between the three speakers surrounding the 2D source position using areal coordinates. FIG. 5 is a perspective view of the 3D multilayer speaker arrangement 1. FIG. 6 is a top view of the 3D multilayer speaker arrangement 1. FIG. 7 is a top view of the 3D multilayer speaker arrangement 1 without the level L.sub.1.

LIST OF REFERENCES

(54) 1 multilayer speaker arrangement 2 speaker 3 control unit A audience area source elevation angle .sub.B blend angle .sub.L1 layer elevation angle .sub.L31 1 layer elevation angle .sub.O opening angle difference angle difference angle EDV.sub.L1 elevation direction vector EDV.sub.L31 1 elevation direction vector g.sub.L0 layer gain factor g.sub.L1 layer gain factor g.sub.L1 layer gain factor g.sub.L layer gain factor g.sub.U layer gain factor i, j, k unit length vector L.sub.0 speaker layer L.sub.1 speaker layer L.sub.1 speaker layer n.sub.L vertical pan n.sub.L1 final vertical pan N.sub.L layer number PIP.sub.L1 panning intersection point PIP.sub.L1 panning intersection point r ratio RP reference point SC.sub.L1 speaker coefficient SC.sub.L1 speaker coefficient SC.sub.L1.sub._.sub.2D layer specific speaker coefficient SC.sub.L1.sub._.sub.2D layer specific speaker coefficient S.sub.L1 geometrical speaker setup S.sub.L1 geometrical speaker setup SP source position SP.sub.X X component of source position SP.sub.XY projected source position SP.sub.Y Y component of source position SP.sub.Z source height value SV source vector S1 step S2.1 step S2.2 step S2.3 step S3 step S4.1 step S4.2 step S4.3 step S5 step S6 step S7 step X direction Y direction Z direction Z.sub.1 height

Method for controlling a three-dimensional multi-layer speaker arrangement and apparatus for playing back three-dimensional sound in an audience area

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