NAME

ramp - generate an exponential sawtooth waveform

CONTENTS

Syntax
Description
Options
Examples
Copyright

ramp [options]

Generate samples of an exponential sawtooth waveform at a given sample rate.Samples are written on the stdout in binary shorts or floats according tothe ‘type’ option.

1. period, amplitude, duration.

The ‘period’ option sets the period of repetition of the waveform in samples.The ‘duration’ option sets the total duration of the output waveform insamples.Both may be given with time units (s or ms) in which case the time is converted tosamples using the given ‘samplerate’ option.The ‘amplitude’ option sets the height of the waveform.

2. polarity

The ‘polarity’ option is used to set the direction of the ramp:

    polarity=ramp   growing exponential:   A.exp(t-T)   0<=t<=T    polarity=damp   decaying exponential:  A.exp(-t)    0<=t<=T

3. decay

The argument of the exponential is calibrated so that the decay factor isa half-life period.The wave grows/decays to half its given amplitude in the given decay time.

1. Growing exponentials

            ramp polarity=ramp dec=1ms

2. Decaying exponentials

            ramp polarity=damp dec=1ms

3. Half a cycle of an 8ms decaying exponential.

            ramp polarity=damp dec=1ms dur=4ms

4. Modulating a tone with a damped exponential.Note: modulating can be done in floating point using a ramp with unitamplitude, or it can be done in integer arithmetic as below.The scale factor in the ‘merge’ program is used to avoid 16-bit overflow.

            tone period=.5ms      > foo1            ramp pol=damp dec=1ms > foo2            merge op=mult factor=0.01 foo1 foo2 > foo3

5. Modulating a tone with a ramped exponential.The 800Hz tone is modulated with a unit ramped exponential with a 25msrepetition rate and a 4ms half life.

            tone freq=800Hz amp=10000 type=float   > foo1            ramp pol=ramp period=25ms dec=4ms amp=1 type=float > foo2            merge op=mult type=float foo1 foo2  | ftos > foo3

6. Modulating a tone with a damped exponential, and half-wave rectifying togenerate damped pulses.

    tone period=.5ms amp=500 type=float    > foo1    ramp pol=damp dec=1ms amp=1 type=float > foo2    merge op=mult type=float foo1 foo2 | ftos | gate range=min-0 op=0 > foo3

7. Modulating white noise with a ramped exponential.

            noise type=float  > foo1            ramp pol=ramp dec=1ms amp=1 type=float > foo2            merge op=mult type=float foo1 foo2 | ftos > foo3

options tone ptrain noise

Copyright (c) Applied Psychology Unit, Medical Research Council, 1995

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