How to use 'phased.Su​bbandPhase​ShiftBeamf​ormer' from the Phased Array Toolbox for microphone array beamforming?

Hello,

I am trying to use the Phased Array Toolbox for microphone array beamforming.

Following the beamforming overview in [1] , I decided that the most appropriate approach for me would be phase-shift beamforming performed at each frequency band, which is implemented in the 'phased.SubbandPhaseShiftBeamformer'.

However, looking at the documentation [2], I see that the object requires "OperatingFrequency" as input parameter, without defining the term.

A search over the whole user manual give a hint by looking at some examples, that this is the carrier frequency for modulated signals used in radar processing.

What is the "OperatingFrequency" in the domain of microphone array beamforming?

If "OperatingFrequency" doesn't make sense in the case of microphone arrays, does this mean, that I cannot use the 'phased.SubbandPhaseShiftBeamformer'?

Finally, besides the true and tested "delay and sum" are there any other conventional wideband beamformers, which can be used with microphone arrays?

P.S. Just out of curiosity, plugging-in a value of "OperatingFrequency" = 2*fs and plotting the RMS output over a grid of steering angles gives a funny looking plot with criss-crossing bands of high and low levels. In contrast, the same plot with the output of 'phased.TimeDelayBeamformer' produced a smooth looking image with the location of the sound source approximately, where it was expected.

[1] Beamforming Overview - MATLAB & Simulink (mathworks.com)

[2] Subband phase shift beamformer - MATLAB (mathworks.com)