As the beamformer aims at suppressing sources not arriving from the target DOA, an error in the DOA estimate may lead to suppression of the desired source by the beamformer.
It is established in [35] that the performance of a given time-frequency mask depends on two criteria: the amount of preserved target source and the amount of suppressed interfering sources.
The target suppression gain (discussed in Section 4.2.2) for Directional BSS degrades from 20 dB for the target signal at 0 ° to about 10 dB for the target signal at 90 °, where the target suppression performance is still acceptable, but the missing selectivity will suppress interfering sources located close to the target source as well.
The LCMV beamformer requires reference signal(s) represented by linear constraints in order to suppress interfering sources and to preserve target signal(s) from known directions [11].
This is what we aim to do - to work on the noise sources, to suppress the noise sources, to learn the noise sources; and then what remains must be a straight line".
This allows the technology to identify and suppress noise sources that would otherwise interfere with a call.
In the system presented in this paper, the microphone signals are first processed using an MVDR beamformer [17], which aims to suppress sound sources not arriving from the direction of arrival (DOA) of the target speaker, while maintaining a unit gain towards this DOA.
Compared with the existing literature, the main contribution of this article is to propose a structure that is able to suppress all sources of interference present in the FBMC-OQAM system: inter-symbol, inter-subchannel, and multi-user interference; even when the subchannels are frequency selective (highly selective channels, low number of subchannels).
Figure 7 Output stream 3, speech signal from source 3 and interfering speech signals from sources 1 and 2. (a) Output stream 3 of the hybrid algorithm containing a separated speech signal from source 3 and suppressed interfering signals from sources 1 and 2. (b) The separated speech signal from source 3 separately.
It can be seen that the secondary source is suppressed, whereas the target source is highlighted.
