A computer-implemented method including, transmitting a high-spectrum energy wave towards a subject from a first sensor and transmitting a low-spectrum energy wave towards the subject from a second sensor. In response, modulation with a carrier sequence code results in a modulated evoked biological signal. The carrier sequence code has an autocorrelation function. The method includes demodulating the modulated evoked biological signal by calculating a convolution of the modulated evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum. The evoked biological signal spectrum has a peak to sideband ratio as a function of the carrier sequence code. The method includes calculating deviations between each element of the sampled evoked biological signal and the peak to sideband ratio and filtering noise artifacts from the sampled evoked biological signal based on the deviations.