Sediment Acoustics

Abstract

cant papers; those commented upon below happen to be more closely related to my own current interests, and the choice does not imply that the others are not worth equal attention.In a chapter entitled "Review of Selected Models of Speech Perception" (Chap. 6), Dennis Klatt presents a masterly overview of selected models of lexical hypothesis formation from acoustic data. Klatt offers both a description and a reasoned critique of the following models: a revised version of the motor theory (Liberman and Mattingly, 1986); analysis by synthesis using broad phonetic classification for initial lexical search (Zue, 1986); lexical access from phonetic features (Stevens, 1986); the LAFS (Lexical Access from Spectra) model of spectral sequences for words (Klatt 1979(Klatt , 1986; auditory front ends that attempt to model the encoding of speech by the peripheral auditory system; pseudoneural models and other network models such as Trace (Elman and McClelland, 1986); phonetic recognition using features as input to a decision strategy involving fuzzy logical prototypes (Massaro, 1987); the perceptual-pointer "speech is not special" theory (Miller, 1982); and hidden Markov models (Jelinek, 1985).Not surprisingly, Klatt finds his own LAPS model most attractive, since "all the detailed knowledge about the relations between acoustics and word sequences is contained in a network of expected spectral sequences" (p. 217). He grants, however, that it has not been proved that enumeration of alternatives is a feasible approach to the characterization of variability inherent in speech. Klatt recognizes that LAPS is basically an atheoretical approach, and admits that until such time as a working system is constructed, LAPS is no more convincing than several other candidate models.In general, theories of lexical access seem to assume that word boundaries are somehow "given," as they are marked by spaces in a printed text. Klatt's model makes provisions for word boundary detection by assuming, first, that matching at the lexical level is done in terms of spectra, that any phonetic transition can be characterized by a sequence of spectra (or by several alternative spectral sequences), and that phonetic recoding across word boundaries is best represented by a decoding network that enumerates all possible spectral sequences for all possible word combinations (of English) (pp. 193-194). Klatt's model, and most of the others reviewed in the article, are basi-J.

Poroelasticity: parameters reviewed

“…When modelling dynamic pressure changes, the equilibrium equations are expanded by inertial forces, being proportional to the acceleration of the rock particles, and Darcy's Law is modified to account for turbulent flow. A small selection of the discourses in this field are the articles of Biot (1956bBiot ( , 1962, Bodvarsson (1970), Thomsen (1985), Boutin, Bonnet & Bard (1987), and the books of BourbiC, Coussy & Zinszner (1987) and Stoll (1989). Cleary (1978) points out some inherent difficulties that occur with rapid deformations in poroelastic media.…”

An analytical relationship between scattering attenuation and porosity in oceanic crust

“…The distinction between intrinsic and scattering attenuation is important only when the scale length of heterogeneity is comparable to or larger than the propagating wavelength [Richards and Menke, 1983]. Due to the complexity of attenuation mechanisms, few empirical and theoretical relationships link observed measurements of attenuation (either scattering or intrinsic or both) with porosity or other rock properties [Stoll, 1989;Wepfer and Christensen, 1991]. Goldberg and Sun [1997] estimate the scattering attenuation in the upper oceanic crust from seismic to sonic wavelengths using a high-resolution velocity model from downhole logs.…”

Rayleigh waves in a partially saturated poroelastic solid

“…Biot-Stoll model (Stoll & Bryan 1970) is an important mathematical model that takes into account both intergranular losses in solid frame and viscous losses in interstitial fluid. This is a very useful model to study the propagation of attenuated waves in marine sediments (Stoll 1974(Stoll , 1985(Stoll , 1989. Sharma & Gogna (1991) considered this model to study the reflection of attenuated body waves at its plane boundary.…”