Feature Name | Definition | Description and references |
---|---|---|
Mean absolute value (MAV) |
| [25] |
Variance (VAR) |
| [25] |
Wave length (WL) |
| [25] |
Wavelet denoise (WDEN) | θ = σ (0.3936 + 0.1829log2(N)), σ-standard deviation of noise | Symmlet 7 mother wavelet, and hard threshold (θ). |
Energy based on discrete Fourier transformation (DFT) | , where X [k] is DFT of x [n] | [25] |
Autoregressive coefficients (AR) |
| The forward-backward approach. The sum of a least squares criterion for a forward model and the analogous criterion for a time-reversed model is minimized [27]. |
Cepstral coefficients (CEPS) | c1 = -a1
| The cepstrum coefficients (ci), are calculated from AR coefficients (AR model with order P), as proposed in Kang's work [26]. |
Autocorrelation-based, second order processing (HOS2) | , H0-noise only (null hypotesis), H1-presence of signal | Toepliz matrix creation, based on estimate of autocorrelation; singular value decomposition; difference among maximum and minimum eigenvalue (σ) [21]. |
Cumulant-based third order processing (HOS3) | , H0-noise only, H1-presence of signal | Toepliz matrix creation, based on estimate of third order cumulant of a data frame; singular value decomposition; the largest eigenvalue (λ) [21]. |
Autocorrelation minimum value (ACORR) | , L-length of ROW |