Micriphone circular array beamforming Matlab

Hello, recently I am working on the design of microphone array beamforming using convex optimization.I designed the circular array beamforming with the sidelobe suppresion of 20db, 30db, 50db and 100db in the interference direction of 180 degre and 0degre. The result is evident in the beam pattern figure(the sidelobe suppression has reached all the expected db). However when I tested the beamforming on audio data, the maximum db suppression is 30db. Meaning when I set the db to 50 or 100 db, the suppression result is the same as for 30db. I need help to clarify this, maybe I missed some theories and concepts of microphone array beamforming design. Thank you for your reply

[Tsardoz]

Sorry for late reply. I just saw it.

I think the most likely reason is due to tolerances of:

1) microphone sensitivity

2) physical placement

There would be a limit on the maximum suppression due to these. I'd suggest if you can get 30dB you are doing well.

I have been looking for circular array designs - Matlab docs seem to suggest linear. Do you have any references you can point me towards?