DIGITAL LOUDSPEAKER

• US 20180160203A1
• Filed: 06/01/2016
• Published: 06/07/2018
• Est. Priority Date: 06/01/2015
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique, Czech Technical University In Prague, Universite Du Maine
• Original Assignee: Centre National De La Recherche Scientifique, Czech Technical University In Prague, Universite Du Maine
• Inventors: Husnik, Libor, Bequin, Philippe, Lotton, Pierrick
• Granted Patent: US 10,484,765 B2
• Time in Patent Office: Days
• CPC Class Codes: H04R 1/005 using digitally weighted transducing elements
• CPC Class Codes: H04R 2203/12 Beamforming aspects for stereophonic sound reproduction with loudspeaker arrays
• CPC Class Codes: H04R 2217/03 Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407

Abstract

A method for reproducing an acoustic signal from a digital signal, the digital signal being formed of successive bit sequences each having bits representative of the amplitude of an acoustic signal at a time sample, the method including (i) providing a plurality of transducers configured to emit acoustic signals that are wave trains having each a duration lower or equal to the duration of one time sample and including at least one oscillation per time sample, and (ii) successively, for each bit sequence, having each bit associated to at least one of the transducers and independently govern, depending on its value, amplitudes of the acoustic signals emitted by its associated transducers.

Claims

1. Method for reproducing an acoustic signal from a digital signal, the digital signal being formed of successive bit sequences each comprising bits representative of the amplitude of an acoustic signal at a time sample, the method comprising:

providing a plurality of transducers configured to emit acoustic signals that are wave trains having each a duration lower or equal to the duration of one time sample and comprising at least one oscillation per time sample,

successively, for each bit sequence, having each bit associated to at least one of the transducers and independently govern, depending on the value of the bit, amplitudes of the acoustic signals emitted by transducer or transducers associated to the bit, in a manner so as to obtain a carrier wave that is modulated in amplitude according to the digital signal.

2. Method according to claim 1, wherein the acoustic signal emitted by the transducers comprises at least several successive oscillations.

3. Method according to claim 1, wherein the acoustic signal emitted by the transducers is a periodic and alternating signal.

4. Method according to claim 1, wherein the acoustic signal emitted by the transducers is of sinusoidal shape.

5. Method according to claim 1, wherein the fundamental frequency of the acoustic signal emitted by the transducers is in the range of ultrasonic frequencies.

6. Method according to claim 1, wherein each bit sequence comprises quantification bits which define a binary number and indicate a quantified absolute value of the amplitude of the acoustic signal to be reproduced at the time sample associated with the bit sequence.

7. Method according to claim 6, wherein, for each successive bit sequence, one of the value of each quantification bit does not induce any variation of the amplitudes of the acoustic signals emitted by its associated transducers, the other one of the value of each quantification bit induces a variation of the amplitudes of the acoustic signals emitted by its associated transducers.

8. Method according to claim 7, wherein the transducers whose operations are not modified by any quantification bit are at an off default state.

9. Method according to claim 7, wherein, for each bit sequence, the bits of a higher rank of the binary number induce either a greater variation in amplitude for each transducer, a variation in amplitude for more associated transducers, or both, than the bits of lower rank of the binary number.

10. Method according to claim 7, wherein each transducer has the amplitude of its acoustic signal determined by at most one bit value of each bit sequence.

11. Method according to claim 1, wherein each transducer has only two different operating states, one of which is a default state.

12. Method according to claim 1, wherein each transducer has only three different operating states, one of which is a default state.

13. Method according to claim 1, wherein the digital signal is an electromagnetic signal, and wherein the transducers are electro-acoustic transducers driven by an alternative current or an alternative voltage.

14. Method according to claim 1, wherein the transducers are arranged so that the acoustic signals converge at a same focus in phase.

15. Method according to claim 1, wherein the transducers are all arranged facing outwards on a plane surface orthogonal to the axis of a parabolic surface, or are all arranged facing outwards on the internal surface of a sphere.

16. Method according to claim 1, wherein the amplitudes and the shapes of the acoustic signals emitted by the transducers are adapted to produce nonlinear demodulation of the acoustic signals into a lower frequency signal, as in an acoustic parametric array.

17. Method according to claim 1, wherein means of redirection of the signal are arranged at the focus.

19. Method according to claim 2, wherein the acoustic signal emitted by the transducers is a periodic and alternating signal.

20. Method according to claim 8, wherein, for each bit sequence, the bits of a higher rank of the binary number induce either a greater variation in amplitude for each transducer, a variation in amplitude for more associated transducers, or both, than the bits of lower rank of the binary number.

18. A loudspeaker comprising a plurality of transducers configured to emit acoustic signals at a predetermined frequency which is equal or greater than any frequency of sampling of the acoustic signal, and arranged so that said acoustic signals converge at a same focus in phase, the loudspeaker further having a configuration in which a digital signal, being formed of successive bit sequences each comprising bits representative of the amplitude of an acoustic signal at a time sample, is used in a manner so that successively, for each bit sequence, each bit is associated to at least one of the transducers and independently governs, depending on its value, the amplitudes of the acoustic signals emitted by its associated transducers.