Direct digital speaker apparatus having a desired directivity pattern

1. Direct digital speaker apparatus receiving a digital input signal and generating sound accordingly, the apparatus comprising:

an array of pressure-producing elements; and

a controller operative to compute a timing pattern determining if and when each pressure-producing element is actuated so as to achieve a desired directivity pattern,

wherein said elements move harmonically and have a single amplitude and a single frequency,

and wherein each said pressure-producing element is operative to produce both positive pressure pulses and negative pressure pulses.

2. A method for controlling direct digital speaker apparatus receiving a digital input signal and generating sound accordingly, the method comprising:

providing an array of pressure-producing elements, and

computing a timing pattern determining if and when each pressure-producing element is operative to produce pressure pulses so as to achieve a desired directivity pattern,

wherein said elements move harmonically and have a single amplitude and a single frequency.

3. Apparatus according to claim 1 wherein each pressure-producing element comprises a moving element, operating to travel alternately back and forth along a respective path.

4. Apparatus according to claim 1 and also comprising a user interface receiving a desired directivity pattern from a user.

5. Apparatus according to claim 1 wherein said directivity pattern is omni-directional defining a focal point.

6. Apparatus according to claim 1 wherein said directivity pattern is cylindrical defining a focal axis.

7. Apparatus according to claim 1 wherein said directivity pattern is unidirectional defining an angle of propagation.

8. Apparatus according to claim 1 wherein said directivity pattern comprises a combination of a plurality of unidirectional directivity patterns.

9. Apparatus according to claim 3 wherein said array defines a plane and wherein said timing pattern comprises employing a suitable delay for at least some of said pressure-producing elements, using the formula: delay=[(d 2 +r 2 )0.5−d]/c, where r=distance between a projection of a focal point onto the array of pressure-producing elements and a given pressure-producing element, d=the distance of the plane of the array of the pressure-producing elements from the focal point, and c=the speed of sound propagation through a medium in which the apparatus is operating.

10. Apparatus according to claim 1 wherein each of said pressure-producing elements is individually controlled.

11. A method according to claim 2 wherein said array providing and said computing are performed a plurality of times thereby to obtain a corresponding plurality of arrays and a corresponding plurality of timing patterns defining a corresponding plurality of directivity patterns; the method also comprising operating said arrays simultaneously in accordance with said corresponding plurality of timing patterns respectively thereby to obtain a single directivity pattern comprising a combination of the directivity patterns corresponding to said plurality of timing patterns.