# Pysound simple square waves

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- pysound

In this example, we will create a simple square wave.

This process is quite similar to the way we create a sine wave, it is worth reading that first.. The way we create a graph of the function, and the way we vary the amplitude and frequency are identical, so we won't repeat them here.

However, square waves have an extra parameter, the `ratio`

, that determines the on/off time of the wave. This creates waves with different shapes, and and similar but different sounds.

## The code

Here is the code:

from pysound.buffer import BufferParams from pysound.oscillators import sine_wave from pysound import soundfile from pysound.graphs import Plotter params = BufferParams() out = square_wave(params, frequency=500) soundfile.save(params, 'square-500.wav', out)

This works in a similar way to the sine wave example, but it uses the `square_wave`

function instead:

out = square_wave(params, frequency=500)

It is stored as *square-500.wav* in the current folder.

Here is what the sound looks like:

This sound is a lot harsher and more electronic sounding than a sine wave.

## Changing the ratio of the square wave

A square wave only has two values, on or off (which are +1.0 and -1.0 in this case). By default, it spends half its time on, and half its time off.

We can change this using the `ratio`

parameter. The ratio specifies the on time as a proportion of the total wave time. A square wave, above, has a ratio of 0.5 (it is on for 50% of the time, therefore off for 50% of the time). The `ratio`

parameter defaults to 0.5, so if you don;t specify it you will get a square wave.

We can change the ratio like this:

out = square_wave(params, frequency=500, ratio=0.2) soundfile.save(params, 'pulse-500.wav', out)

In this case, the ratio is 0.2 (it is on for 20% of the time, therefore off for 80% of the time). Of course it is also possible to create a wave that is on for longer than it is off (for example a ratio of 0.6 gives a wave that is one for 60% of the time, off for 40%).

A wave with unequal of/off times is sometimes called a pulse wave. Here is what the 0.2 case looks like: