Ultra-directional microphones
OwnerJames A. Moorerinventor
Life of this patent
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Abstract
The present invention provides a highly directional audio response that is flat over five octaves or more by the use of multiple colinear arrays followed by signal processing. Each of the colinear arrays has a common center, but a different spacing so that it can be used for a different frequency range. The response of the microphones for each spacing are combined and filtered so that when the filtered responses are added, the combined response is flat over the selected frequency range. To improve the response, the output of the microphones for a given array spacing can also be filtered with windowing functions. To receive the response from other directions a “steering” delay may also be introduced in the microphone signals before they are combined. The invention also extends to two and three dimensional arrays.
Claims13
A microphone system comprising:
- a plurality of collinear microphones regularly spaced according to pluralities of distinct spacings with a common center;
- a plurality of microphone signal adders, wherein the microphones of each set of microphones having one of said spacings are connected to the same signal adder;
- a plurality of first filters, each connected to receive an output of a corresponding one of the microphone signal adders;
- a plurality of second filters each connected to an output of one of the microphones such that each microphone is connected to a microphone signal adder through the second filter, wherein each of the second filters implements one of a plurality of windowing functions that are each a function of one of the pluralities of spacings associated with the one of the microphones with which the second filter is connected;
- and
- an output adder connected to receive the output of the first filters and supply the combined signal as an output, wherein the frequency response of the first filters is such that the combined signal is flat over a selected frequency range in a selected direction.
Dependencies are inferred from the claim text.