Fundamental Frequency

[blue fish]

In the getting started section of the first lab, it asks:

What are the differences between sine_100Hz.wav, sine_200Hz.wav and sine_300Hz.wav ?
– measure the time between 2 adjacent peaks in the waveform and
calculate their fundamental frequency

I am confused to as why we need to calculate the fundamental frequency of the waves as it’s already given in the file names.

[Simon]

Measuring the fundamental period for yourself from the waveform is a learning exercise, and so is calculating the fundamental frequency from the fundamental period. Real waveforms don’t tell you their fundamental frequency in their filename!

This task is very easy for the sine wave, pulse train, and square wave. But it’s not always quite so easy for the speech waveform, as you will discover when you try it for yourself.

[blue fish]

Can you tell me whether or not this is correct for the 100Hz sine wave:

Its fundamental frequency is 100Hz because, since it’s time between two peaks is 0.01 seconds, there must be 100 cycles per second.

[Simon]

Yes – that’s correct.

[blue fish]

Also I did not mean that the file names always had the frequency in it! I just thought it was a weird task since the frequencies were in the sine files and it was simple to calculate the frequencies.

[Simon]

Sure – it’s a very simple task, but it does require you to learn how to use Wavesurfer, which is something you’ll need later in the course.

[Author]

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