The kazoo, a wind instrument, generates its typical sound when stimulated by voiced speech. Using this instrument, this paper proposes a novel technique to recover the glottal pulse excitation of its player. We applied multiband frequency techniques to the kazoo signal to compare the results with those obtained from the corresponding recordings of an electroglottograph (EGG). With the player's management over his embouchure on the instrument, one can make recordings for spoken and singing speech as well as recitative, at the instrument’s resonator cap, which closely fit the EGG recordings. After a spectrogram analysis, it was possible to detect in the lower frequency band of the kazoo signals, the spectral envelope and, in the higher frequency band, the pitch harmonics mixed with the spectral decay of the glottal pulse. A quadrature mirror filter (QMF) was designed, providing this source-filter separation. Additionally, a reverse spectral band replication (SBR) technique was applied, which consists in recovering the lower frequency band by the demodulation of the higher frequency band followed by a total energy spectral gain adjustment, where a new signal was generated and then evaluated. At the end, a subjective evaluation, SNR, and SD measures prove the efficiency of the proposed method.
Physical layer security (PLS) is an alternative to traditional information security mechanisms. Physical layer secret key generation (PSKG) is a PLS technique that uses channel randomness to generate keys for encryption algorithms. Although several works investigated PSKG in slow fading channels, fast fading scenarios remain a challenge. We propose two predictors to deal with such scenarios, one based on the Recursive Least Squares (RLS) and another based on the Dual Extended Kalman Filter (DEKF). The aim is to mitigate the channel variation effects during PSKG, reducing the errors between keys generated by legitimate users.
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