Sound system for video screens
A sound system for use with a non-acoustically transparent video screen ( 1 ) is disclosed, comprising at least one loudspeaker enclosure ( 10 ) comprising a loudspeaker ( 15 ) arranged so that the main direction of propagation of the sound ( 33 ) which it emits is directed towards said screen, the sound being reflected by the surface of the screen towards an audience ( 2 ). The enclosure ( 10 ) further comprises a second sound emitter ( 16/20 ) situated at the rear of said loudspeaker ( 15 ), whereby the loudspeaker enclosure has a directivity of the cardioid type. The second sound emitter may, for example, comprise an opening, combined with a defined quantity of acoustically absorbent material ( 17 ) arranged inside the enclosure ( 10 ) between the rear of the loudspeaker ( 15 ) and the opening ( 16 ); alternatively, it may comprise at least one second loudspeaker ( 20 ) situated so as to be substantially directed towards the audience ( 2 ), said second loudspeaker ( 20 ) being connected with a reversed polarity with respect to the principal loudspeaker ( 15 ).
1. A sound system comprising a screen, said screen being a non-acoustically transparent video screen, said sound system further comprising a loudspeaker enclosure fixed to the ceiling of a room or placed on the ground, said loudspeaker enclosure comprising a loudspeaker arranged so that a main direction of propagation of a sound emitted by said loudspeaker is directed towards said screen, said sound being reflected by a surface of said screen towards an audience, characterized in that said loudspeaker enclosure further comprises a second sound emitter situated at the rear of said loudspeaker adapted to emit sound in phase opposition to said sound emitted in said main direction of propagation by said loudspeaker, whereby said loudspeaker enclosure has a directivity selected from semi-cardioid type and semi-hypercardioid type, with the level of emitted sound being at a maximum in the direction of said screen and at a minimum in the direction of said audience.
2. The sound system according to claim 1 , wherein said second sound emitter comprises an opening in said loudspeaker enclosure situated at the rear of said loudspeaker and a defined quantity of an acoustically absorbent material arranged inside said loudspeaker enclosure between the rear of said loudspeaker and said opening.
3. The sound system according to claim 2 , characterized in that said defined quantity of said acoustically absorbent material is adjusted so that an axis of minimum sound radiation defining said directivity of said loudspeaker enclosure is substantially oriented in a direction toward said audience.
4. The sound system according to claim 2 , wherein said opening has a surface area at least equal to half of an emissive surface area of said loudspeaker.
5. The sound system according to claim 4 , characterized in that said defined quantity of said acoustically absorbent material is adjusted so that an axis of minimum sound radiation defining said directivity of said loudspeaker enclosure is substantially oriented in a direction toward said audience.
6. The sound system according to claim 1 , wherein said loudspeaker constitutes a principal loudspeaker and wherein said second sound emitter comprises a second loudspeaker situated so as to be substantially directed towards said audience, said second loudspeaker being connected with a reversed polarity with respect to said principal loudspeaker.
7. The sound system according to claim 6 , wherein said second loudspeaker receives a signal which is modified with respect to a signal received by said principal loudspeaker, said signal received by said second loudspeaker being delayed, equalized and low-pass filtered by a digital processing means so as to reduce a sound level emitted by said sound system along an axis substantially oriented toward said audience.
8. The sound system according to claim 1 , wherein said loudspeaker enclosure is fixed to the ceiling of a room.
9. The sound system according to claim 8 , wherein said loudspeaker enclosure has a front face inclined at an angle between 15° and 45° with respect to vertical axis, so that said loudspeaker is directed towards said screen when said loudspeaker enclosure is fixed to said ceiling.
10. The sound system according to claim 1 , wherein said loudspeaker enclosure has an asymmetrical shape about a vertical axis, so that said loudspeaker is directed towards said screen when said loudspeaker enclosure is placed on the ground.
11. The sound system according to claim 1 , wherein said loudspeaker enclosure comprises a plurality of loudspeakers.
12. The sound system according to claim 1 , comprising at least three identical said loudspeaker enclosures directed towards said screen, each of said loudspeaker enclosures receiving an individual signal.