The name is absent

13

SignaIGeneration

During experiments, one of two types of stimulus is desired, either a long pulse
at a specific frequency of sinusoid, which creates a "buzzing" sensation, or an
instantaneous "tap" stimulus.

Pulse generation

The pulse signal is constructed by the software used to run the experiments,
Presentation (www.neurobs.com). The signal is created as a sound and then fed into an
amplifier from the sound card's headphone jack. However_zWhenPresentation
generates sinusoids, it starts the sinusoid at an unknown phase, which can result in
extreme ramp rates at the onset and cessation of the sinusoid (Fig. 7A). This causes a
very rapid flex in the piezoelectric bending actuator that creates a loud click and a
strong tactile impulse. To correct this the sinusoid is multiplied by a windowing function
constructed by playing the first quarter phase of a 5Hz sinusoid, followed by a DC signal,
followed by the second quarter phase of a 5Hz sinusoid (Fig. 7B), giving the waveform
shown in Fig. 7C. The results in an electrical signal that still has a relatively pure
frequency spectrum (Fig. 8), in fact more pure than the waveform shown in 2.1.7A, and
eliminates the high ramp rates that cause the mechanical disturbances in the
piezoelectric bending actuator. An example of a generated IOOHz pulse as recorded by
oscilloscope is shown if Fig. 8.

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