I am designing a audio gating cct to gate the outpt frm codec ADC port. I need the mesuare the signal to noise ratio of the circuit to determine my circuit isnt noisy since my entire board contains digital circt and digital gnd is noisy. So can any one guide me how do i do the mesuarement to make sure my cct is nt noisy assuming i have audio analyser, osciloscope. Could any one guide me on this. Thanks