Meeting Room Microphone Array Characteristics

When using multichannel enhancement techniques to improve speaker diarization in the meetings environment one usually encounters a set of characteristics in the meeting room data that will condition the practical implementation of the system.

1. Microphone array definition: In a meeting the microphones are set in different positions of the room. Some microphones are in the meetings table, some are in the room walls and in some occasions the attendees are wearing head-mounted or lapel microphones. Such multiplicity of types and positions defies the standard concept of microphone array as analyzed in the theory. The lack of a single/optimum microphone, which obtains a clean signal from all participants, makes acoustic beamforming using all available microphones a feasible and worthwhile application for these microphones. Such implementation needs to be sufficiently general to fit such loose microphone array definition.

2. Number of elements: The number of acoustic channels (microphones) available for processing varies from meeting to meeting, not necessarily being kept constant for meetings coming from the same source. The implementation cannot impose any constraint in the number of channels it requires for processing, and should optimally obtain an ``enhanced'' signal with better quality than either one of the individual signals alone.

3. Different microphone qualities: The frequency response of the different microphones in the meeting room cannot be considered equal as these can be of multiple types. One needs to consider possible differences in the contribution of each of the microphones according to their signal quality, either known a priory or computed automatically by the system.

4. Microphone locations: The exact location of the microphones in the room is unknown. In some cases one can know the relationship between the positions of certain microphone groups (for example microphones within a circular microphone array or a linear array). The microphone settings change for each meeting room and it should not be necessary to know them a priory.