A system of reducing echoes resulting from acoustic coupling, the system comprising:
- a sound pick-up device having a signal output;
- a sound reproduction device;
- an application unit having an input connected to said signal output of said sound pickup device and having an output connected to an input of said sound reproduction device, said sound reproduction device adapted to reproduce said signal output from said sound pick-up device;
- said sound pick-up device including at least two sound sensors situated at different distances from said sound reproduction device and further including a processing unit adapted to process signals outputted from said at least two sound sensors and to output said sound pick-up device signal output to said application unit, said processing unit reducing an echoes in said sound pick-up device signal output caused by acoustic coupling between said sound pickup device and said sound reproduction device;
- said processing unit including a filter adapted to filter an output signal from each of said at least two sound sensors and a summer adapted to sum a filtered output signal from each of said at least two sound sensors;
- wherein each filter of said processing unit has a pulse response defined by a function gi(t) that is a solution calculated once and for all of the following equation:
- ∑ i [ h i ( t ) * g i ( t ) ] ≈ 0
- for i varying from 1 to n, wherein n is a positive integer equal to the number of sensors;
- and
- wherein hi(t) is a previously obtained impulse response of each of said at least two sensors to signals outputted by said reproduction device is for i varying from 1 to n, and wherein* represents a convolution operation.