Need help to understand harmonics and spectrogram

Special Interest Groups Audio Processing
1

Hello experts,

I have simple understanding Problem. I try to make an Audio recording of 2kHz sinus and Motor. I’m waiting to get harmonics 2f, 3f, …, nf
But I see just a 1f, 3f, 5f. Why is it happens? Where can I read more about?

See attachment please!
On the 1. picture: It’s a recording of my motor system with 2kHz Buzzer on beginning
On the 2. picture: This is just a generated 2 kHz tone with tone generator (here I can see very little line on 2f and 4f)

Thank you very much!
Best regards, NR

img_021.jpeg
img_020.jpeg

2

Perhaps your expectation was incorrect.

The harmonics in a square wave are the odd harmonics: Square wave - Wikipedia


Below is a screenshot using Audacity 2.4.0 alpha (it allows the waveform and spectrogram view to be displayed at the same time).
The waveform is a 2kHz alias free square wave. Note the harmonics at 3f, 5f, 7f, 9f.

First Track000.png
First Track000.png978×553 25.6 KB

3

Oh, thank you very much! Yes, I think it was a wrong expectation of my.
I will read more about this topic!

Sincerely yours,
NR

P.S. I will open a new topic about another Question about Motors