Focused parametric array

• US 20050195985A1
• Filed: 02/24/2005
• Published: 09/08/2005
• Est. Priority Date: 10/29/1999
• Status: Abandoned Application

• Current Assignee: American Technology Incorporated (Emerson Electric Company)
• Original Assignee: American Technology Incorporated (Emerson Electric Company)
• Inventors: Croft, James J. III, Liu, Wensen
• Application Number:
  US11/065,698
• Publication Number:
  US 20050195985A1
• Time in Patent Office: Days
• US Class Current: 381/77
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: H04R 2217/03 Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves

Abstract

A parametric sound system for creating an acoustical column along an axis of propagation having a quiet zone an audible zone is disclosed. The system comprises a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves. A plurality of decoupled acoustic waves are maximized at a focalizing area within the audible zone. The system also includes a signal source for applying a parametric ultrasonic signal to the parametric electroacoustic emitter. The signal includes an ultrasonic carrier signal and one or more sideband signals corresponding to an audio input signal. The system further comprises a signal processor for controlling phases of the parametric ultrasonic signal so that the plurality of focalized parametric ultrasonic waves emitted by the parametric electro-acoustic emitter will create a quiet zone along the same direction of propagation as the audible zone. The plurality of decoupled audio waves are substantially in phase within the audible zone while the plurality of decoupled audio waves are largely out-of-phase within the quiet zone.

Claims

1. ) A method for increasing acoustic amplitude at lower audio frequencies of resultant decoupled audio waves from a parametric loudspeaker, the method comprising:

a) configuring adjacent, isolated emission zones of the parametric loudspeaker configured to emit parametric ultrasonic waves at an operating frequency so that when the parametric ultrasonic waves are emitted from the isolated emission zones, wherein resultant decoupled audio waves will have an increased acoustic amplitude at lower audio frequencies of the decoupled audio waves relative to higher audio frequencies of the decoupled audio waves; and

b) applying one or more parametric ultrasonic signals to the adjacent, isolated emission zones, wherein each emission zone has a periodic change in phase from an adjacent zone, enabling the parametric ultrasonic waves to be substantially phase coherent within a predetermined focalizing area, wherein phases of a majority of the parametric ultrasonic waves emitted from the emission zones are configured to arrive within approximately 90°

of one another within the predetermined focalizing area, enabling the parametric ultrasonic waves to constructively interfere within the predetermined focalizing area to increase an acoustic output of the parametric ultrasonic waves within the predetermined focalizing area.

2. ) The method of claim 1, further comprising the step of configuring the adjacent, isolated emission zones as a center isolated conductive emission strip and a parallel emission strip on both sides of the center isolated emission strip, the parallel emission strips being located at progressively further distances from the center isolated emission strip.

3. ) The method of claim 1, further comprising the more specific step of configuring the adjacent, isolated emission zones as a center isolated emission zone and at least one concentric outer-ring isolated emission zone.

4. ) The method of claim 1, wherein the adjacent, isolated emission zones are comprised of Electrically Sensitive and Mechanically Responsive (ESMR) film configured for emitting parametric ultrasonic waves.

5. ) The method of claim 1, wherein the isolated emission zones are comprised of a plurality of bimorph transducers configured for emitting parametric ultrasonic waves.

6. ) The method of claim 1, further comprising the step of positioning all adjacent, isolated emission zones on a single plane.

7. ) The method of claim 6, further comprising the step of applying the one or more parametric ultrasonic signals to a center isolated emission zone at approximately 0°

phase, and incrementing a phase of the one or more parametric ultrasonic signals applied to each successive outer adjacent emission zone by approximately 180°

.

8. ) The method of claim 6, further comprising the step of applying the one or more parametric ultrasonic signals to a center isolated emission zone at approximately 0°

phase, and incrementing a phase of the one or more parametric ultrasonic signals applied to each successive outer adjacent emission zone by approximately 90°

.

9. ) The method of claim 6, comprising the step of applying the one or more parametric ultrasonic signals to a center isolated emission zone at approximately 0°

phase, and incrementing a phase of the one or more parametric ultrasonic signal applied to each successive outer adjacent emission zone by approximately 45°

.

10. ) The method of claim 1, comprising the step of positioning at least one outer emission zone on a separate plane relative to an adjacent emission zone, wherein one or more planes of a plurality of the adjacent, isolated emission zones are located at different distances from the predetermined focalizing area, such that the phases of all emitted parametric waves are within approximately 90°

within the predetermined focalizing area.

11. ) A parametric sound system for increasing acoustic amplitude at lower audio frequencies at a predetermined focalizing area, comprising:

a) an electro-acoustic emitter capable of emitting parametric ultrasonic waves, and having a series of adjacent, isolated emission zones;

b) a signal source for supplying parametric ultrasonic signals to each adjacent, isolated emission zone; and

c) wherein each adjacent, isolated emission zone is sized and positioned to operate at a predetermined operating frequency, and phases of each parametric ultrasonic signal applied to each emission zone are configured such that the parametric ultrasonic waves emitted from each emission zone will arrive at the predetermined focalizing area within approximately a 90°

phase difference, resulting in a plurality of decoupled audio waves having increased acoustic amplitude at lower audio frequencies relative to higher audio frequencies of the decoupled audio waves.

12. ) The parametric sound system of claim 11, wherein the adjacent, isolated emission zones more specifically comprise a center isolated conductive emission strip and a plurality of parallel emission strips on both sides of the center isolated conductive emission strip, each of the plurality of parallel emission strips being located at progressively further distances from the center emission strip.

13. ) The parametric sound system of claim 11, wherein the adjacent isolated, emission zones more specifically comprise a center isolated emission zone and at least one concentric outer-ring isolated conductive emission zone.

14. ) The parametric sound system of claim 11, wherein the adjacent, isolated emission zones are comprised of electrically sensitive and mechanically responsive (ESMR) film configured for emitting parametric ultrasonic waves, wherein one side of the ESMR film is coupled to a support member.

15. ) The parametric sound system of claim 14, wherein at least one portion of an outer electrode coupled to the ESMR film is etched away to create the adjacent, isolated emission zones.

16. ) The parametric sound system of claim 15, wherein the outer electrode coupled to the ESMR film having at least one etched portion is facing outward from the support member.

17. ) The parametric sound system of claim 15, wherein the outer electrode coupled to the ESMR film having at least one etched portion is facing toward the support member.

18. ) The parametric sound system of claim 14, wherein each emission zone is comprised of a portion of an entire ESMR film, with etched portions between each adjacent emission zone to create the adjacent, isolated emission zones.

19. ) The parametric sound system of claim 14, further comprising a printed circuit board coupled to the support member, the printed circuit board having electrical contacts for coupling the signal source to each adjacent, isolated emission zone.

20. ) The parametric sound system of claim 11, wherein the adjacent, emission zones are comprised of a plurality of bimorph transducers configured for emitting parametric ultrasonic waves.

21. ) The parametric sound system of claim 11, wherein the parametric ultrasonic signal is applied to a center isolated emission zone at approximately 0°

phase, and the phases applied to each successive outer adjacent emission zone are alternated between approximately 180°

out-of-phase and approximately 0°

out-of-phase with respect to an inner adjacent emission zone.

22. ) The parametric sound system of claim 11, wherein the parametric ultrasonic signal is applied to a center isolated emission zone at approximately 0°

phase, and a phase of the parametric ultrasonic signal applied to each successive outer adjacent emission zone is increased by approximately 90°

.

23. ) The parametric sound system of claim 11, wherein the parametric ultrasonic signal is applied to a center isolated emission zone at approximately 0°

phase, and the phase of the parametric ultrasonic signal applied to each successive outer adjacent emission zone is increased by approximately 45°

.

24. ) The parametric sound system of claim 11, further comprising a switch for disabling phase differentials of the parametric ultrasonic signals applied to each emission zone such that all signals are applied at approximately 0°

phase differential, thereby creating a parametric ultrasonic wave that is not focalized to the predetermined focalizing area.

25. ) The parametric sound system of claim 24, more specifically comprising a fading switch for gradually switching the parametric ultrasonic wave between a focalized wave and a non-focalized wave.

26. ) A parametric sound system for increasing amplitude at lower audio frequencies, comprising:

a) an electro-acoustic emitter capable of emitting parametric ultrasonic waves, and having at least a center circular isolated emission zone and one or more concentric outer-ring isolated emission zone;

b) a signal source for supplying a parametric ultrasonic signal to each of the one or more isolated emission zone;

c) wherein radii of outer and inner bounds of each of the one or more isolated emission zones are constructed to operate at a predetermined operating frequency; and

d) wherein the parametric ultrasonic waves decouple to produce acoustic waves, wherein the acoustic waves have an increased acoustic amplitude at lower acoustic frequencies relative to higher frequencies of the acoustic waves.

27. ) A parametric sound system for focalizing a parametric ultrasonic wave, comprising:

a) an electro-acoustic emitter capable of emitting parametric ultrasonic waves, and having a plurality of isolated emission zones comprising a center circular isolated emission zone and at least one concentric outer-ring isolated emission zone;

b) a signal source for supplying a parametric ultrasonic signal to each isolated emission zone wherein each emission zone has a periodic change in phase from an adjacent zone;

c) wherein location of a focalizing area is a function of the phase of each emission zone and a radius of outer and inner bounds of each of the isolated emission zones; and

d) wherein the radius of each of the isolated emission zones are sized such that all emitted parametric waves will arrive at the focalizing area within approximately a 90°

range with respect to the phase of other parametric waves in the focalizing area.

28. ) A method for creating a wideband focalization of an audio wave, comprising:

a) providing a phased emitter having a plurality of adjacent emission zones and having an operating frequency;

b) applying a parametric ultrasonic signal to the phased emitter to produce a parametric ultrasonic wave, wherein the parametric ultrasonic signal comprises a carrier signal and at least one sideband signal, wherein the at least one sideband signal corresponds to an audio input signal; and

c) emitting the parametric ultrasonic wave at an intensity sufficient to drive a surrounding medium into nonlinearity such that interaction of the at least one sideband signal with the carrier signal in the nonlinear medium creates audio waves having a frequency corresponding to a difference of the carrier signal and the at least one sideband signals, and having increased amplitude at lower frequencies of the audio waves relative to upper frequencies of the audio waves.

29. ) The method of claim 28, further comprising setting the carrier frequency approximately at the operating frequency for increased energy efficiency at the carrier frequency.

30. ) The method of claim 28, further comprising offsetting the operating frequency from a resonant frequency of a plurality of phased emitters by a predetermined frequency amount to an offset operating frequency to increase output efficiency at the offset operating frequency.

31. ) A method for reducing length of an audio column of a parametric loudspeaker when used in an air medium, comprising:

a) providing an electro-acoustic emitter with a central emission zone and one or more outer emission zones adjacent to the central emission zone;

b) configuring the one or more outer emission zones to be in a different plane than the central emission zone to enable each emission zone to have a periodic change in phase from an adjacent zone;

c) applying a parametric ultrasonic signal to the emission zones to emit a corresponding parametric ultrasonic wave into a surrounding air medium; and

d) driving the surrounding air medium into non-linearity, thereby creating a plurality of decoupled audio waves having a phase coherency that is maximized at a predetermined length from the electro-acoustic emitter, wherein the phase of the plurality of decoupled audio waves becomes largely incoherent at a set distance beyond the predetermined length.

32. ) A method for creating a quiet zone interposed between at least two audible zones along a direction of propagation, comprising:

a) providing a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, wherein a plurality of decoupled acoustic waves are maximized at a focalizing area within a predefined audible zone, the plurality of decoupled acoustic waves having increased amplitude at lower frequencies of the plurality of decoupled audio waves relative to the higher frequencies of the plurality of decoupled audio waves;

b) applying a parametric ultrasonic signal to the parametric electro-acoustic emitter, including a carrier signal set substantially near an operating frequency of the parametric electro-acoustic emitter and one or more sideband signals corresponding to an audio input signal;

c) emitting the plurality of focalized parametric ultrasonic waves at an intensity sufficient to drive a surrounding medium into nonlinearity, thereby creating the plurality of decoupled acoustic waves; and

d) controlling a phase alignment of the parametric ultrasonic signal to create a quiet zone interposed between, and along the same direction of propagation as at least two audible zones, wherein the plurality of decoupled audio waves are substantially in-phase in the at least two audible zones, and the plurality of decoupled audio waves are substantially out-of-phase in the quiet zone.

33. ) The method of claim 32, comprising the more specific step of providing a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, having a central circular isolated emission zone and at least one concentric outer-ring isolated emission zone.

34. ) The method of claim 33, comprising the more specific step of providing a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, having a central circular isolated emission zone and at least one concentric outer-ring isolated emission zone, wherein there is an even number of emission zones.

35. ) A method for creating a quiet zone directly following, and along a same direction of propagation as an audible zone, comprising:

a) providing a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, wherein a plurality of decoupled acoustic waves are maximized at a focalizing area within a predefined audible zone, the plurality of decoupled acoustic waves having increased amplitude at lower frequencies of the plurality of decoupled acoustic waves relative to the higher frequencies of the plurality of decoupled acoustic waves;

b) applying a parametric ultrasonic signal to the parametric electro-acoustic emitter, including a carrier signal set substantially near an operating frequency of the parametric electro-acoustic emitter and one or more sideband signals corresponding to an audio input signal;

c) emitting the plurality of focalized parametric ultrasonic waves at an intensity sufficient to drive a surrounding medium into nonlinearity, thereby creating the plurality of decoupled acoustic waves; and

d) controlling a phase alignment of the parametric ultrasonic signal to create the quiet zone directly following, and along the same direction of propagation as the audible zone, wherein the plurality of decoupled acoustic waves are substantially in phase in the audible zone, and the plurality of decoupled acoustic waves are substantially out-of-phase in the quiet zone.

36. ) The method of claim 35, comprising the more specific step of providing a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, having a central circular isolated emission zone and at least one concentric outer-ring isolated emission zone.

37. ) The method of claim 36, comprising the more specific step of providing a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, having a central circular isolated emission zone and at least one concentric outer-ring isolated emission zone, wherein there is an odd number of emission zones.

38. ) A parametric sound system for creating a quiet zone along a same direction of propagation as an audible zone, comprising:

a) a parametric electro-acoustic emitter configured for emitting a plurality of focalized parametric ultrasonic waves, wherein a plurality of decoupled acoustic waves are maximized at a focalizing area within the audible zone, the plurality of decoupled acoustic waves having increased amplitude at lower frequencies of the decoupled audio waves relative to higher frequencies of the decoupled audio waves;

b) a signal source for applying a parametric ultrasonic signal to the parametric electro-acoustic emitter, wherein the parametric ultrasonic signal includes an ultrasonic carrier signal and one or more sideband signals corresponding to an audio input signal; and

c) a signal processor for controlling phases of the parametric ultrasonic signal so that the plurality of focalized parametric ultrasonic waves emitted by the parametric electro-acoustic emitter will create a quiet zone along the same direction of propagation as the audible zone, wherein the plurality of decoupled audio waves are substantially in phase within the audible zone, and the plurality of decoupled audio waves are largely out-of-phase within the quiet zone.

39. ) The parametric sound system of claim 38, more specifically comprising a signal processor for controlling phases of the parametric ultrasonic signal so that the plurality of focalized parametric ultrasonic waves will create a quiet zone interposed between, and along the same direction of propagation as at least two audible zones, wherein the plurality of decoupled audio waves are substantially in phase within the at least two audible zones, and the plurality of decoupled audio waves are largely out-of-phase within the quiet zone.

40. ) The parametric sound system of claim 38, more specifically comprising a signal processor for controlling phases of the parametric ultrasonic signal so that the plurality of focalized parametric ultrasonic waves will create a quiet zone directly following, and along the same direction of propagation as the audible zone, wherein the plurality of decoupled audio waves are substantially in phase within the audible zone, and the plurality of decoupled audio waves are largely out-of-phase within the quiet zone.

41. ) A parametric sound system configured for creating a plurality of focalized decoupled audio waves, comprising:

a) an electro-acoustic emitter configured for emitting a plurality of ultrasonic wave-fronts including carrier wave components at a carrier wave frequency and sideband wave components at a sideband wave frequency, wherein phases of all carrier wave components arriving at a focalizing area are substantially aligned, and wherein the sideband wave components at frequencies near the carrier wave frequency arrive at the focalizing area having greater phase alignment and greater amplitude than the sideband wave components at frequencies that depart from the carrier wave frequency; and

b) a signal source configured for driving the electro-acoustic emitter at a level sufficient for the plurality of ultrasonic wave fronts to drive a surrounding medium into nonlinearity such that interaction of the sideband wave components with the carrier wave components creates the plurality of decoupled, focalized audio waves having maximized phase coherency at the focalizing area and having an audible frequency corresponding to a difference between the carrier wave frequency and the sideband wave frequency, and the plurality of decoupled, focalized acoustic waves having increased amplitude at lower frequencies relative to higher frequencies of the plurality of decoupled, focalized acoustic waves due to a greater phase alignment in the focalizing area of the plurality of decoupled audio waves at frequencies near the carrier wave frequency.