Estimating the Spectral Envelope of Voiced Speech Using Multi-Frame Analysis
This paper proposes a novel approach for estimating the spectral envelope of voiced speech independently of its harmonic structure. Because of the quasi-periodicity of voiced speech, its spectrum indicates harmonic structure and only has energy at frequencies corresponding to integral multiples of F_0. It is hence impossible to identify transfer characteristics between the adjacent harmonics. In order to resolve this problem, Multi-frame Analysis (MFA) is introduced. The MFA estimates a spectral envelope using many portions of speech which are vocalised using the same vocal-tract shape. Since each of the portions usually has a different F_0 and ensuing different harmonic structure, a number of harmonics can be obtained at various frequencies to form a spectral envelope. The method thereby gives a closer approximation to the vocal-tract transfer function.