Cascade implementation of CANFs in spectral analysis of short data auditory evoked brainstem responses

Auditory evoked brainstem response (ABR) can be modeled as two closely spaced sinusoids immersed in noise. Conventional methods on the FFT are often not useful in the spectral estimation of short-duration ABRs. The authors propose the use of constrained adaptive notch filters (CANFs) implemented as a cascade of second-order sections, and discuss two special configurations based on CANF combined with a constrained notch filter (CNF) with fixed parameters. The problem associated with the convergence of the direct-form implementation of higher-order CANFs to a local minimum is also addressed. The methods proposed are shown to provide reliable spectral estimation and enhancement of the real data ABRs