A personal computer programmable sine-wave generator

A programmable sine-wave generator has been developed that permits microcomputer control of both discrete and continuous variations in the frequency and amplitude of auditory, visual, or vibrotactile stimuli. The function and design of the sine-wave generator as a peripheral to the Apple II/FIRST system are detailed. Moreover, adaptations of the basic sine-wave circuit are briefly described for interfacing it with other microcomputers (e.g., the IBM PC and compatibles), and for altering the waveform, range, and resolution of the output. Sample programs in Apple II/FIRST and Applesoft BASIC for controlling signal frequency and amplitude are used to illustrate the simplicity of programmable control. The sine-wave generator has many of the capabilities of commercially available ones, at a fraction of the cost.     

A pseudorandom noise generator for use in auditory research

A noise generator that is capable of delivering long-duration samples of reproducible noise is described. The noise is generated as a pseudorandom telegraph waveform but may be filtered so that its amplitude distribution is approximately Gaussian. The design and construction of the generator are detailed and a few possible applications are given.     

Haptic detection of sine-wave gratings

We studied human haptic perception of sine-wave gratings. In the first experiment we measured the dependence of amplitude detection thresholds on the number of cycles and on the wavelength of the gratings. In haptic perception of sine-wave gratings, the results are in agreement with neural summation. The rate at which detection thresholds decrease with increasing number of cycles is much higher than can be accounted for by probability summation alone. Further, neural summation mechanisms describe the detection thresholds accurately over the whole spatial range probed in the experiment, that is wavelengths from 14 mm up to 225 mm. Earlier, we found a power-law dependence of thresholds on the spatial width of Gaussian profiles (Louw et al, 2000 Experimental Brain Research 132 369-374). The current results extend these findings; the power-law dependence holds not only for Gaussian profiles, but also for a broad range of sine-wave gratings with the number of cycles varying between 1 and 8. Haptic perception involves tactual scanning combined with an active, dynamic exploration of the environment. We measured characteristics of the velocity and force with which stimuli were scanned while performing a psychophysical task. One particularly surprising finding was that, without being instructed, participants maintained an almost constant scanning velocity during each 45-min session. A constant velocity in successive trials of the experiment might facilitate or even be necessary for discrimination. Further, a large systematic dependence of velocity on scanning length was found. An eightfold increase in scanning length resulted in about a fourfold increase in scanning velocity. A second experiment was conducted to study the influence of scanning velocity on psychophysical detection thresholds. This was done by systematically imposing specific scanning velocities to the participants while the thresholds were measured. The main result of the second experiment was that psychophysical detection thresholds are constant over a relatively broad range of scanning velocities.     

A programmable multiple-tone generator

A simple tone generator that allows software control of auditory stimuli is described. The circuit provides for the simultaneous generation, timing, and amplification of three different tones. Its low cost, ease of construction, and versatility make it an attractive alternative to conventional auditory stimulus hardware.     

Auditory-phonetic projection and lexical structure in the recognition of sine-wave words

Speech remains intelligible despite the elimination of canonical acoustic correlates of phonemes from the spectrum. A portion of this perceptual flexibility can be attributed to modulation sensitivity in the auditory-to-phonetic projection, although signal-independent properties of lexical neighborhoods also affect intelligibility in utterances composed of words. Three tests were conducted to estimate the effects of exposure to natural and sine-wave samples of speech in this kind of perceptual versatility. First, sine-wave versions of the easy and hard word sets were created, modeled on the speech samples of a single talker. The performance difference in recognition of easy and hard words was used to index the perceptual reliance on signal-independent properties of lexical contrasts. Second, several kinds of exposure produced familiarity with an aspect of sine-wave speech: (a) sine-wave sentences modeled on the same talker; (b) sine-wave sentences modeled on a different talker, to create familiarity with a sine-wave carrier; and (c) natural sentences spoken by the same talker, to create familiarity with the idiolect expressed in the sine-wave words. Recognition performance with both easy and hard sine-wave words improved after exposure only to sine-wave sentences modeled on the same talker. Third, a control test showed that signal-independent uncertainty is a plausible cause of differences in recognition of easy and hard sine-wave words. The conditions of beneficial exposure reveal the specificity of attention underlying versatility in speech perception.     

Metamotivational states displayed using differential digital photoplethysmograms while listening to music and noise

The theory of psychological reversal postulates that individuals switch between paratelic and telic metamotivational states. To observe the paratelic state as an actual phenomenon using a physiological index, a correlation between changes in P-wave amplitudes of differential digital photoplethysmograms (deltaDPG) of 24 undergraduate students while listening to music and changes in mood pre- to postlistening was investigated. Elevation in arousal of the sympathetic nervous system, as indicated by deltaDPG. was related to improvement in mood. It was assumed that the subjects who were aroused more while listening to music enjoyed the high arousal more and were more susceptible to a pleasant state. This was interpreted as a paratelic state. In listening to a noise condition using another 24 undergraduate students, however, the correlation was inverse of that for the music condition. It was assumed that the subjects who spent more effort in identifying stimuli showed more elevation in arousal of the sympathetic nervous system and more aggravation in mood. This was interpreted as a telic state.     

A Constant-current AC shock generator

A device has been developed for the effective delivery of a preset constant current AC electric shock. The shock intensity is adjustable from zero to a maximum of 10 ma as the voltage varies between 0 to 5 kv. The 5-kv, 60-HZ, AC voltage insures a constant-current output regardless of skin contact resistance changes. Shock duration is internally controlled and a “fail safe” lockout circuit to render the apparatus inoperative is provided in case of accidental sticking or failure of control relay signals from either internal circuitry or from behavioral programming equipment.     

Visual field effects in the discrimination of sine-wave gratings

The time needed to decide whether the second of two successively presented sinusoidal gratings was of a higher or lower spatial frequency than the first was measured for spatial frequencies of 1, 2, 4, 8, and 12 cycles per degree (cpd) presented in either the left visual field (LVF) or right visual field (RVF). A LVF advantage was found for discriminating within the low-spatial-frequency range (i.e., 1 and 2 cpd), whereas a RVF advantage was found for discriminating within the high-spatial-frequency range (i.e., 4-12 cpd). These findings support the conclusion that hemispheric asymmetries in the processing of gratings arise when comparisons are made between the output of spatial-frequency channels.     

A test-signal generator for low-frequency instrumentation

An instrument for generating simultaneous sinusoidal test signals m the range of 1–32 Hz for EEG equipment checkout procedures is described. A composite signal is produced by a method that separates the functions of waveform generation and control of output frequencies at which that waveform appears. The general technique may be applicable in a number of situations involving low-frequency instrumentation, as with other types of physiological monitoring. Possibilities and methods for elaboration or modification of the circuit are suggested.     

A simple inexpensive computer-controlled tone generator

A simple circuit for a keyed tone generator is described. The total construction cost is less than $5. Various adaptations and modifications of the circuit are discussed.     

Wuggy: A multilingual pseudoword generator

Pseudowords play an important role in psycholinguistic experiments, either because they are required for performing tasks, such as lexical decision, or because they are the main focus of interest, such as in nonwordreading and nonce-inflection studies. We present a pseudoword generator that improves on current methods. It allows for the generation of written polysyllabic pseudowords that obey a given language’s phonotactic constraints. Given a word or nonword template, the algorithm can quickly generate pseudowords that match the template in subsyllabic structure and transition frequencies without having to search through a list with all possible candidates. Currently, the program is available for Dutch, English, German, French, Spanish, Serbian, and Basque, and, with little effort, it can be expanded to other languages.     

A random-pulse generator with adjustable pulse duration

An electronic device for generating random pulses of adjustable duration within a minimal and maximal interval boundary is described. The instrument is useful in electro- and psychophysiological research where randomization of stimulus input is required.     

A simple,inexpensive stimulus waveform generator

A simple circuit for a sine wave generator is described. The total cost for construction is approximately $30.00. At present, the unit is used to generate a sinusoidally modulated light stimulus for steady state visual evoked response experiments. Modifications of the circuit for other applications are discussed.     

A digital ultrasound recorder

A system that continuously monitors and records rodent ultrasonic vocalizations over the frequency range 10–90 kHz is described. The system records vocal frequency, sound pressure, time, and duration of call. Data are stored digitally. The system was validated by a pilot study in which distress calls of rat pups were selectively activated while they were subjected to a cold environment.