I am working on conventional frequency domain beamforming for linear microphone receive array. I have simulated 32 channels array data with a poin target at 45 deg emiiting 20KHz tonal. I performed beamforming to make 32 beam time series data.

To calculate array gain (or beamformer gain) I compare the 20 kHz tonal level in individual channel data and in 45degree beam time series data. Problem is that array gain/beamformer gain calculated in this way is approximately 16dB above theoretical array gain (i.e. 10*log10 (32) = 15dB).

Can any one kindly guide me where I am wrong?

Note: I have tried many simulations with different parameters but results were same.

THANKS