This paper presents an acoustic model-based lossy pole-zero modeling for speech signals, which overcomes the limitation in the existing lossless pole-zero model that forced the numerator part of the pole-zero transfer function to be symmetric. We derive the lossy pole-zero model and its transfer function by employing the wave digital filter (WDF) adaptor formulas and by converting the fixed termination value -1 to a loss factor /spl mu//sub 0//sup c//spl isin/(-1, 1). Then we discuss how to determine the reflection coefficients of the lossy pole-zero model. For this we first employ a well-performing ARMA modeling algorithm for a pole-zero type estimation of the given speech signal and then fit the transfer function of the lossy pole-zero model to that of the ARMA model under Euclidean cost function. This procedure is demonstrated by an example using the Steiglitz-McBride ARMA estimation method with a synthetic speech signal. The lossy pole-zero modeling yields a new filter structure-namely, three-branch lattice structure-which consists of three lattice branches with the third branch terminated by the loss factor /spl mu//sub 0//sup c//spl isin/[-1, 1] and with the three branches connected by a three-port wave adaptor characterized by the area ratio /spl sigma//spl isin/ [0,1]. The three-branch lattice structure is a general filter structure which becomes the lossless pole-zero structure when /spl mu//sub 0//sup c/=-1 and becomes the existing all-pole lattice structure when /spl sigma/=0.

In this paper we present a new digital filter structure which enables a practical realization of finite-wordlength low-sensitivity digital filters. It is a cascade structure consisting of Type I and Type 2 LBR two-pairs interlacing each other, and is called a two-type-interlaced structure. In addition, an LBR test is introduced as a means to determine the LBRness of the quantized two-type-interlaced structure. The proposed structure and the LBR test are applied to the conventional digital filters. The results show that perfect LBRness can always be maintained with the proposed structure.>

The authors establish a theory for lossless pole-zero modeling of speech signals for the description of nasal sounds. The theory is based on a generalized vocal tract tube model which consists of the main vocal tract, the oral tract, and the nasal tract. A pole-zero type transfer function, which turns out to be a generalized version of the existing all-pole type transfer function, is derived. Fundamental properties of the generalized vocal tract model are investigated, employing the concept of discrete-time reactance. A procedure for evaluating the reflection coefficients for the model is outlined. The assumption of losslessness in the modeling leads to the following two properties. First, the combination of two lattice structures representing the oral and the nasal tracts form one larger lattice structure when viewed at their joint point called the branch boundary. Second, the oral and the nasal tract render respective discrete-time reactances whose convex combination generates the discrete-time reactance at the branch boundary. The first property enables the combined reactance to be computed, and the second helps separate it into its components.>