A method for the generation of complex vibrotactile stimuli

A method is described utilizing computer-generated sine wave data and purpose-built hardware to generate a complex vibrotactile stimulus. Two sine waves of different frequency were summed to produce a complex waveform with two temporal components, a high frequency component and a low frequency beat component. The computer-generated data points for each of the two component sine waves were downloaded to two banks of static memory in a dual synchronous arbitrary function generator. The data points in memory were fed to two 12-bit digital-to-analogue converters which sent the two analogue sine wave signals to a summing amplifier where the two sine waves were added. This method provides a complex waveform that can be gated on and off, has a fixed frequency ratio of the component sine waves and no phase drift between the component waves. Addition of the separate sine waves in a summing amplifier allows for easy alteration of the amplitude ratio of the sine waves. The output of the summing amplifier is sent to a feedback controlled mechanical stimulator, thereby allowing the stimulus to be presented to the skin of human subjects and experimental animals.