Teleconferencing system with visual feedback

• US 6,173,059 B1
• Filed: 04/24/1998
• Issued: 01/09/2001
• Est. Priority Date: 04/24/1998
• Status: Expired due to Term

• Current Assignee: Gentner Communications Corp. (Clearone Incorporated)
• Original Assignee: Gentner Communications Corp. (Clearone Incorporated)
• Inventors: Huang, Jixiong, Grinnell, Richard S.
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): ZINTEL, HAROLD ALBERT
• Application Number:
  US09/066,163
• Time in Patent Office: 991 Days
• Field of Search: 381/92, 367/118, 367/119, 367/121, 367/122, 367/124, 367/126, 379/202
• US Class Current: 381/92
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2201/401 2D or 3D arrays of transducers

Abstract

A telephone system includes two or more cardioid microphones held together and directed outwardly from a central point. Mixing circuitry and control circuitry combines and analyzes signals from the microphones and selects the signal from one of the microphones or from one of one or more predetermined combinations of microphone signals in order to track a speaker as the speaker moves about a room or as various speakers situated about the room speak then fall silent. Visual indicators, in the form of light emitting diodes (LEDs) are evenly spaced around the perimeter of a circle concentric with the microphone array. Mixing circuitry produces ten combination signals, A+B, A+C, B+C, A+B+C, A−B, B−C, A−C, A−0.5(B+C), B−0.5(A+C), and C−0.5(B+A), with the “listening beam” formed by combinations, such as A−0.5(B+C), that involve the subtraction of signals, generally being more narrowly directed than beams formed by combinations, such as A+B, that involve only the addition of signals. An omnidirectional combination A+B+C is employed when active speakers are widely scattered throughout the room. Weighting factors are employed in a known manner to provide unity gain output. Control circuitry selects the signal from the microphone or from one of the predetermined microphone combinations, based generally on the energy level of the signal, and employs the selected signal as the output signal. The control circuitry also operates to limit dithering between microphones and, by analyzing the beam selection pattern, may switch to a broader coverage pattern, rather than switching between two narrower beams that each covers one of the speakers.

Claims

1. A microphone system for use in an environment where an acoustic source emits energy from diverse and varying locations within the environment, comprising:

at least two directional cardioid microphones held in a fixed arrangement about a center point, the respective response of each of the microphones being directed radially away from the center point, the microphones producing electrical signals in response to acoustic signals,

mixing circuitry for combining electrical signals from the microphones to form a set of composite electrical signals, each composite electrical signal corresponding to a predetermined acoustic reception pattern wherein at least some of the predetermined acoustic reception patterns corresponding to the set of composite electrical signals have different spatial shapes and sizes, and

control circuitry for analyzing the signal energy value of each composite electrical signal in the set to thereby determine an acoustic reception pattern which best fits the angular orientation and physical pattern of the acoustic source relative to the central point and to select the corresponding composite electrical signal for transmission.

2. The microphone system of claim 1 wherein the control circuit substantially continuously analyzes the composite electrical signals and selects for transmission the composite electrical signal corresponding to the acoustic reception pattern having the highest energy value.

3. The microphone system of claim 2 wherein the control system determines the best fit substantially as the composite electrical signal related to the acoustic response pattern having the highest average filtered energy value over a given time period.

4. The microphone system of claim 3 wherein the control system alters the selection of the composite electrical signal to be transmitted only if the most recent best fit value exceeds the prior best fit value by a predetermined amount.

5. The microphone system of claim 4 wherein the control system selects a composite electrical signal corresponding to a combination of microphones having a relatively broad acoustic response pattern that substantially encompasses acoustic response patterns that the control system has recently been switching between.

6. The microphone system of claim 1 wherein the microphone array is a substantially coplanar array of microphones.

7. The microphone system of claim 1 wherein the microphone array comprises three cardioid microphones space 120 degrees apart.

8. The microphone system of claim 7 wherein the acoustic response patterns include a combination formed by adding the acoustic response patterns of two of the microphones.

9. The microphone system of claim 8 wherein the acoustic response patterns include a combination formed by adding the acoustic response patterns of all three microphones.

10. The microphone system of claim 1 further comprising:

a visual indication system controlled by the control system such that the control system produces a visual signal indicative of which acoustic response pattern has been chosen.

11. The microphone system of claim 10 wherein the visual indication system comprises a ring of LEDs concentric with the microphones.

12. In a microphone system for use in an environment where an acoustic source moves about the environment, a method comprising the steps of:

(a) providing at least two directional cardioid microphones held iii a fixed arrangement about a center point, the respective response of each of the microphones being directed radially away from the center point, the microphones producing electrical signals in responses to acoustic signals,

(b) producing a sequence of samples for each microphone corresponding to the electrical signals,

(c) combining sequences of samples from at least two microphones, thereby producing a set of composite sequences of samples, each sequence corresponding to a predetermined acoustic reception pattern, wherein at least some of the predetermined acoustic reception patterns corresponding to the set of composite sequences have different spatial shapes and sizes,

(d) partitioning the composite sequences into subsequences of at least one sample each,

(e) computing an energy value for each subsequence,

(f) comparing the energy values for all subsequences partitioned from all composite sequences in the set, thereby determining the subsequence corresponding to an acoustic reception pattern which best fits the angular orientation and physical pattern of the acoustic source relative to the central point, and

(g) selecting an electrical signal corresponding to a composite sequence from which the determined subsequence is partitioned for transmission.

13. The method of claim 12 wherein step (f) comprises the step of:

(f1) substantially continuously [analyzing the electrical signals] comparing the energy values for each subsequence.

14. The method of claim 13 wherein step (f) comprises the step of:

(f2) selecting for transmission the electrical signal corresponding to the acoustic reception pattern having the highest energy value.

15. The method of claim 13 wherein step (f) comprises the step of:

(f3) selecting for transmission the electrical signal corresponding to the acoustic reception pattern having the highest average filtered energy value over a given time period.

16. The method of claim 15 wherein step (f3) comprises the step of

(f3a) altering the selection of the electrical signal to be transmitted only if the most recent best fit value exceeds the prior best fit value by a predetermined amount.

17. The method of claim 16 wherein step (f3) comprises the step of:

(f3b) selecting an electrical signal corresponding to a combination of microphones having a relatively broad acoustic response pattern that substantially encompasses acoustic response patterns that the control system has recently been switching between.

18. The method of claim 12 wherein step (a) comprises the step of:

(a1) providing at least three directional cardioid microphones held in a fixed arrangement about a center point spaced apart at equal angles, the respective acoustic response of each of the microphones being directed radially away from the center point.

19. The method of claim 12 further comprising the step of:

(h) producing a visual signal indicative of which acoustic response pattern has been chosen.