Chapter 12

Introduction to Visual Sensations

Part I of this book considers the basis for auditory perceptual qualities and preferences, especially as they relate to architectural acoustics. The auditory primary sensations were classified as either temporal or spatial sensations, which are described in terms of a signal-processing model of the central auditory system. The model consists of a monaural autocorrelation mechanism (ACF) and a binaural crosscorrelation mechanism (IACF). The temporal factors extracted from the ACF associated with the left hemisphere and the spatial factors extracted from the IACF associated with the right hemisphere, respectively, effectively describe temporal and spatial sensations. Such specializations of human cerebral hemispheres play an important role in making temporal and spatial factors independent with respect to subjective judgments. The auditory temporal sensations are loudness, pitch (missing fundamental), timbre, and duration sensations. The auditory spatial sensations include sound localization, apparent sound width (ASW), and subjective diffuseness (envelopment).

Part II considers perceptual qualities and preferences in vision. Visual sensations can be considered in terms of temporal and spatial sensations that are based on analogous correlation mechanisms, and similar methods can be used to assess their associated subjective preferences. The visual temporal sensation of flicker rate is analogous to auditory pitch and the missing fundamental phenomenon (Fujii et al., 2000). Considerable physiological and psychological evidence exists for temporal autoand crosscorrelation representations in vision and in many other sensory modalities (Cariani, 2001). The visual spatial sensations include contrast, regularity, and coarseness of the focal vision (Fujii et al., 2003), as well as localization. Visual sensations in relation to temporal factors may well be described in terms of brain activities (Soeta et al., 2002a, b; Soeta et al., 2002). Table 12.1 summarizes temporal and spatial sensations in vision as well as their subjective preferences. The table provides the features of temporal and spatial autocorrelation representations that are thought to be associated with each visual perceptual attribute, as well as their corresponding neural activity observables and the sections in this volume where they are discussed.