Monocular masking studies show that the visibility of a one-dimensional sinusoidal grating remains unchanged in the presence of masking noise filtered so as to contain spectral components that are at least two octaves away from the spatial frequency of the grating (Stromeyer and Julesz 1972). In the present study, random-dot stereograms were bandpass filtered in the two-dimensional Fourier domain, and masking noise of various spatial frequency bands was added to the filtered stereograms. Masking noise bands containing equally effective noise energy were selected such that their bands were either overlapping with the stereoscopic image spectrum or were two octaves distant. The first case resulted in binocular rivalry; however, in the second case stereoscopic fusion could be maintained in the presence of strong binocular rivalry owing to the masking noise. This finding indicates that spatial-frequency-tuned channels are not restricted to one-dimensional gratings but operate on two-dimensional patterns as well. Furthermore, these frequency channels are utilized in stereopsis and work independently from each other, since some of these channels can be in binocular rivalry while at the same time other channels yield fusion. The main binocular experiments are demonstrated.

A study of vowel sounds by means of a spectral analysis keyed synchronously to the voice pitch has been carried out. Spectra are obtained by Fourier analysis of individual pitch periods which were established by visual inspection of oscillograms. A digital computer served as the analyzer. The spectra are represented by a pattern of zeros and poles obtained by a process of successive approximation, again carried out by computer. The contributions from vocal tract and glottal source can be uniquely separated and examined. These results show that vowel sounds can be represented by a sequence of poles arising from the vocal tract and a sequence of zeros charactering the izglottal excitation. The frequencies of the vocal tract poles agreed with previous measurements, but the damping factors were not entirely consistent with earlier estimates. The zeros showed approximately uniform frequency spacing, particularly at high frequencies. A theoretical development indicated that this characteristic was to be expected from the known structure of the glottal excitation. The zero pattern was used to estimate the ratio of open-to-closed time for the glottis during voicing. PEECH is the acoustic result of certain events in the vocal apparatus. Indeed, many of the characteristics of these events can be deduced from the acoustical properties of the speech itself. For instance,it has been long realized that speech formants are a reflection of vocal tract resonances, and that the quasi-periodic nature of vocalized speech can be attributed directly to the vocal cord excitation. Usually, such features have been studied with the aid of the sound spectrograph and other special instruments. Though of great utility, these instruments have limitations, both in the range and flexibility of their analysis parameters, and in the dynamic range and resolution of their output displays.With the advent of digital computers as analysis tools, much more sophisticated processing and display have become possible. 2'a This paper presents a basic speech spectrum analysis 4'5 which takes advantage of the greater resources of the computer. The results indicate that this analysis leads to a much more precise acoustic representation of the speech wave than heretofore feasible. Consequently, this representation can be tied quite accurately to vocal tract events.In the first step of the analysis the speech time waveform is segmented into pitch periods which are then subjected to a Fourier expansion. The resulting spectrum is approximated by a number of resonances (poles) and antiresonances (zeros). Utilizing the assumption that each period is one of an infinite sequence of identical periods, this "pitch synchronous" representation can be related easily and precisely to vocal characteristics. In particular, the physical constraints imposed by the known structure of the vocal tract permit the • This paper is the written version of a talk given at the 58th Publishing Company, Amsterdam, 1960). 179 poles and zeros to be assigned uniquely to either the vocal tract...

Objective.—This review article is designed to thoroughly familiarize all health care professionals with the history, classification, epidemiology, clinical characteristics, differential diagnosis, diagnostic evaluation (including laboratory-based testing), treatment, and prognosis of botulism. It is especially targeted toward clinical laboratorians and includes a detailed enumeration of the important clinical laboratory contributions to the diagnosis, treatment, and monitoring of patients with botulism. Finally, the bioterrorism potential for botulism is discussed, with an emphasis on the clinical laboratory ramifications of this possibility. Data Sources.—Included medical periodicals and textbooks accessioned from computerized and manual medical literature searches. More than 1000 medical works published from the 1800s through 2003 were retrieved and reviewed in this process. Data Synthesis.—Pertinent data are presented in textual and tabular formats, the latter including 6 tables presenting detailed information regarding the clinical parameters, differential diagnosis, diagnostic studies, laboratory testing, and therapeutic approaches to botulism. Conclusions.—Because botulism is such a rare disease, a keen awareness of its manifestations and prompt diagnosis are absolutely crucial for its successful treatment. The bioterrorism potential of botulism adds further urgency to the need for all health care professionals to be familiar with this disease, its proper evaluation, and timely treatment; the need for such urgency clearly includes the clinical laboratory.

Spatial models of functions of two variables are often a valuable research tool. Nomograms and artistic relief drawings in two dimensions are difficult to prepare and still lack the direct impact of a spatial object. It has been demonstrated (see Ref. 2) that objects with a randomly dotted surface permit the determination of binocular parallax and, thus, can be seen in depth even though they are devoid of all other depth cues. This random surface presentation has the advantage that the random brightness points can be evenly and densely placed, whereas the classical contour‐line projection at equally spaced heights may leave empty spaces between adjacent contour‐lines. A digital computer is used to generate the three‐dimensional image of a given z = f (x, y) function and to wrap its surface with points of random brightness. The stereo projections of the function are obtained and, when viewed stereoscopically, give the impression of the three‐dimensional object as being viewed along the z‐axis. The random surface prevents the accumulation of clusters of uniform regions or periodic patterns which yield ambiguities when fused. Two stereo demonstrations are given of surfaces obtained by this method.

Considerable attention has been given of late to the source function, its properties and significance. Consequently, a method of pitch-synchronous analysis, reported on previously, has been improved and applied more extensively to gather additional data on the volume-velocity function of the glottis. The technique arises from the model of vocalic sounds in which the spectra are characterized by a separation of vocal-tract poles from glottal-source zeros. A Fourier analysis is made on one period of the pressure wave, the formants are located and removed from the spectrum, and the glottal waveform is computed from the residual by Fourier synthesis. This approach requires digital recordings free from phase distortion and with a high signal-to-noise ratio. Data from six male talkers in varying contexts and at different pitches and intensities have been studied with attention to shape, phase with respect to the speech wave, duty factor and degree of closure as a function of talker, sound, pitch, and intensity.