Interesting graphs; eigenbeams with higher orders have more low
frequency noise, without much impact on beam forming.
Marc
Le 18/08/2018 à 19:20, Steven Backer a écrit :
Following up on the insightful comments from Fons et al. -
The increase or decrease in noise relative to the self-noise of a single mic is
often referred to in the literature as White Noise Gain (WNG). This can be
calculated or measured for linear filtering operations such as Ambisonics
B-format encoding or virtual microphone beamforming. Lower numbers are worse;
negative values indicate an increase in noise level relative to a single omni
mic, and positive values indicate a reduction in relative noise level.
For the Eigenmike, we take this into account as a design constraint in our
software, and even give the user a few options to trade off this constraint
against the operating regions of the higher-order signals. We did post some
documents specifying the WNG (as a function of frequency) on our website not
too long ago, both for the B-format encoding (“Eigenbeams”) as well as the
virtual microphones (“Modal Beamformers”). This is specific to our hardware
and software and may differ in others’ implementations.
Eigenbeams:
https://mhacoustics.com/sites/default/files/Eigenbeam%20Datasheet_R01A.pdf
<https://mhacoustics.com/sites/default/files/Eigenbeam%20Datasheet_R01A.pdf>
Modal Beamformer:
https://mhacoustics.com/sites/default/files/Beamformer%20Datasheet_R02A.pdf
<https://mhacoustics.com/sites/default/files/Beamformer%20Datasheet_R02A.pdf>
-Steven
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