Variable pattern microphone system

• US 4,888,807 A
• Filed: 01/18/1989
• Issued: 12/19/1989
• Est. Priority Date: 01/18/1989
• Status: Expired due to Fees

• Current Assignee: Audio Technica U.S. Inc (Audio-Technica Corporation)
• Original Assignee: Audio Technica U.S. Inc (Audio-Technica Corporation)
• Inventors: Reichel, Kenneth R.
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US07/298,068
• Time in Patent Office: 335 Days
• Field of Search: 381/92, 381/113, 381/26, 381/169, 381/170
• US Class Current: 381/92
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2410/01 Noise reduction using microphones having different directional characteristics
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A microphone system including a plurality of sound transducers integrally contained in a single microphone housing, wherein each transducer has a different polar pick-up pattern. The system includes a remote combiner for the symmetrical addition of the output of each transducer into a composite signal of variable pattern. In the illustrated implementation, the system includes an electret microphone capsule having an omnidirectional pick-up pattern, an electret microphone capsule having a cardioid pick-up pattern, and an electret microphone capsule having a hypercardioid pick-up pattern. The capsules each have a mechanical acoustic phase shifting element to produce the desired pick-up patterns and are time aligned in the housing by placing the capsules together at the same location while pointing in the same direction. Each capsule has an independent power supply module and adjustable gain amplifier for the acoustical balancing of the system which is also integrally contained in the microphone housing. The combiner is shown implemented as a resistive switching network allowing the selection of multiple patterns, and alternatively, as a number of rheostats connected at a common node thereby providing an infinitely variable selection of patterns.

Claims

1. A variable pattern microphone system comprising:

a first sound transducer with an omnidirectional pick-up pattern;

a second sound transducer with a cardioid pick-up pattern;

a third sound transducer with a hypercardioid pick-up pattern;

means for equalizing the phase and acoustical balance between said first transducer and said second and third transducers to produce a first equalized output;

means for equalizing the phase and acoustical balance between said second transducer and said first and third transducers to produce a second equalized output;

means for equalizing the phase and acoustical balance between said third transducer and said first and second transducers to produce a third equalized output; and

means for combining said first, second and third equalized outputs to provide a combined signal having a selectable pick-up pattern from the microphone system.

2. A variable pattern microphone system as set forth in claim 1 which further includes:

means for amplifying said combined signal in the selected pattern.

3. A variable pattern microphone system as set forth in claim 1 wherein said means for combining include:

a SP3T switch having three switch contacts and a pole contact, wherein said first equalized output is connected to one of the switch contacts, said first equalized output is connected to another of the switch contacts through an impedance, and the other switch contact is not connected;

a DP4T switch having four pairs of switch contacts and two pole contacts, wherein a first pair of switch contacts are not connected, a second pair of switch contacts has one contact connected to said second equalized output and the other contact not connected, a third pair of switch contacts has one contact connected to said third equalized output and the other contact not connected, and a fourth pair of switch contacts has one contact connected to said second equalized output and the other contact connected to said third equalized output; and

wherein the pole contact of said SP3T switch and the pole contacts of said DP4T switch are connected together.

4. A variable pattern microphone system as set forth in claim 1 wherein said means for combining include:

a common node;

a first variable impedance connected between said first equalized output and said common node;

a second variable impedance connected between said second equalized output and said common node; and

a third variable impedance connected between said third equalized output and said common node.

5. A variable pattern microphone system as set forth in claim 1 wherein:

said first, second, and third transducers and said means for equalizing the phase and acoustical balance between said first, second, and third transducers are contained integrally in a single microphone housing.

6. A variable pattern microphone system as set forth in claim 5 wherein:

said transducer are positioned in close proximity to each other in said microphone housing.

7. A variable patter microphone system as set forth in claim 6 wherein:

said transducers are pointed substantially in the same direction in said microphone housing.

8. A variable pattern microphone system as set forth in claim 5 wherein:

said means for combining are located remotely from said single microphone housing.

9. A variable pattern microphone system as set forth in claim 8 wherein said means for combining include:

a SP3T switch having three switch contacts and a pole contact, wherein said first equalized output is connected to one of the switch contacts, said first equalized output is connected to another of the switch contacts through an impedance, and the other switch contact is not connected;

a DP4T switch having four pairs of switch contacts and two pole contacts, wherein a first pair of switch contacts are not connected, a second pair of switch contacts has one contact connected to said second equalized output and the other contact not connected, a third pair of switch contacts has one contact connected to said third equalized output and the other contact not connected, and a fourth pair of switch contacts has one contact connected to said second equalized output and the other contact connected to said third equalized output; and

wherein the pole contact of said SP3T switch and the pole contacts of said DP4T switch are connected together.

10. A variable pattern microphone system as set forth in claim 8 wherein said means for combining include:

a common node;

a first variable impedance connected between said first equalized output and said common node;

a second variable impedance connected between said second equalized output and said common node; and

a third variable impedance connected between said third equalized output and said common node.

11. A variable pattern microphone system having a microphone housing connected to a remote means for pattern modification by a microphone cable, wherein said microphone housing integrally includes:

a plurality of electret microphone capsules, each capsule having a variable capacitance, a preamplifier, and a mechanical phase filter means for determining the pick-up pattern of the capsule; and

a plurality of equalizing means, each corresponding to a separate capsule for balancing the output signal from a respective preamplifier against those of the other capsules to produce respective first, second, and third equalized outputs;

wherein said capsules point in substantially the same direction and are positioned in close proximity to each other in said microphone housing;

wherein each of said capsules has a different pick-up pattern; and

wherein said means for pattern modification includes means for linearly combining the output signals from said equalizing means.

12. A microphone system as defined in claim 11 wherein said means for combining includes:

a SP3T switch having three switch contacts and a pole contact, wherein said first equalized output is connected to one of the switch contacts, said first equalized output is connected to another of the switch contacts through an impedance, and the other switch contact is not connected;

a DP4T switch having four pairs of switch contacts and two pole contacts, wherein a first pair of switch contacts are not connected, a second pair of switch contacts has one contact connected to said second equalized output and the other contact not connected, a third pair of switch contacts has one contact connected to said third equalized output and the other contact not connected, and a fourth pair of switch contacts has one contact connected to said second equalized output and the other contact connected to said third equalized output; and

wherein the pole contact of said SP3T switch and the pole contacts of said DP4T switch are connected together.

13. A microphone system as defined in claim 11 wherein said means for combining include:

a common node;

a first variable impedance connected between said first equalized output and said common node;

a second variable impedance connected between said second equalized output and said common node; and

a third variable impedance connected between said third equalized output and said common node.

14. A microphone system as defined in claim 11 wherein said plurality of capsules include:

a first transducer capsule with an omnidirectional pick-up pattern;

a second transducer capsule with a cardioid pick-up pattern; and

a third transducer with a hypercardioid pick-up pattern.