Method and apparatus for reconstruction of soundwaves from digital signals

• US 20030044029A1
• Filed: 08/16/2002
• Published: 03/06/2003
• Est. Priority Date: 08/17/2001
• Status: Active Grant

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Diamond, Brett M., Gabriel, Kaigham J., Neumann, John J. Jr.
• Granted Patent: US 7,089,069 B2
• Time in Patent Office: Days
• US Class Current: 381/111
• CPC Class Codes: H04R 1/005 using digitally weighted transducing elements

Abstract

Each of a plurality of speaklets (MEMS membranes) produces a stream of clicks (discrete pulses of acoustic energy) that are summed to generate the desired soundwave. The speaklets are selected to be energized based on the value of a digital signal. The greater the significance of the bit of the digital signal, the more speaklets that are energized in response to that bit. Thus, a time-varying sound level is generated by time-varying the number of speaklets emitting clicks. Louder sound is generated by increasing the number of speaklets emitting clicks. The present invention represents a substantial advance over the prior art in that sound is generated directly from a digital signal without the need to convert the digital signal first to an analog signal for driving a diaphragm.

Claims

1. A method of reconstructing a waveform from a multibit digital signal, comprising:

using at least certain of said bits of said multi-bit digital signal to drive a plurality of MEMS membranes.

2. The method of claim 1 additionally comprising organizing said plurality of MEMS membranes into groups in which each group is representative of one bit of the digital signal.

3. The method of claim 2 wherein each group of membranes, except the group representative of the least significant bit, has twice the number of membranes as the group representative of the preceding bit of the digital signal.

4. The method of claim 2 wherein each group consists of at least one membrane and wherein each membrane, except the membrane representative of the least significant bit, has twice the area of the membrane representative of the preceding bit of the digital signal.

5. The method of claim 2 wherein each group, except the group representative of the least significant bit, has twice the effective area as the group representative of the preceding bit of the digital signal.

6. A method of directly constructing a waveform from a multibit digital signal, comprising:

inputting at least certain of said bits to drive electronics to produce drive pulses; and

controlling the position of a plurality of MEMS membranes with said drive pulses.

7. The method of claim 6 additionally comprising organizing said plurality of MEMS membranes into groups in which each group is representative of one bit of the digital signal.

8. The method of claim 7 wherein each group of membranes, except the group representative of the least significant bit, has twice the number of membranes as the group representative of the preceding bit of the digital signal.

9. The method of claim 7 wherein said each group consists of at least one membrane and wherein each membrane, except the membrane representative of the least significant bit, has twice the area of the membrane representative of the preceding bit of the digital signal.

10. The method of claim 7 wherein each group, except the group representative of the least significant bit, has twice the effective area as the group representative of the preceding bit of the digital signal.

11. A method of producing a waveform from a digital signal, comprising:

generating a plurality of discrete acoustic energy pulses with a plurality of MEMS membranes.

12. The method of claim 11 additionally comprising organizing said plurality of MEMS membranes into groups in which each group is representative of one bit of the digital signal.

13. The method of claim 12 wherein each group of membranes except the group representative of the least significant bit has twice the number of membranes as the group representative of the preceding bit of the digital signal.

14. The method of claim 12 wherein said each group consists of at least one membrane and wherein each membrane, except the membrane representative of the least significant bit, has twice the area of the membrane representative of the preceding bit of the multi-bit digital signal.

15. The method of claim 12 wherein each group, except the group representative of the least significant bit, has twice the effective area as the group representative of the preceding bit of the digital signal.

16. A digital sound reproduction apparatus, comprising:

a plurality of MEMS membranes; and

a plurality of drivers for driving said plurality of membranes in response to a digital signal.

17. The apparatus of claim 16 wherein said membranes are organized into subsets, and wherein each of said plurality of drivers is responsive to a bit of a digital signal to drive one of said subsets, each of said subsets, except the subset representative of the least significant bit, has twice the effective area as the subset representative of the preceding bit.

18. The apparatus of claim 17 Wherein the effective area is doubled by doubling the number of said MEMS membranes.

19. The apparatus of claim 17 wherein the effective area is doubled by doubling the size of said MEMS membrane.

20. The apparatus of claim 17 wherein the effective area is doubled by the combination of increasing the number and increasing the size of said MEMS membranes.

21. A device for producing an acoustic wave from a digital signal, comprising:

a plurality of drivers responsive to a digital signal for producing drive pulses representative of said digital signal; and

a plurality of MEMS membranes of substantially the same size responsive to said drive pulses.

22. A device for producing an acoustic wave from a digital signal, comprising:

a plurality of drivers responsive to a digital signal for producing drive pulses representative of said digital signal; and

a plurality of MEMS membranes of different sizes responsive to said drive pulses.