Dual 555 timer musical horn

[ElectricLizzie93]

Hi,

I've just built this circuit http://www.circuitstoday.com/musical-horn-circuit and simulated it in LTSpice (attached) for my lab project. I think I works ok, makes a sort of buzzing sound, but for my report I need to understand how it works. I understand that the left hand chip provides a pulse (the frequency of which depends on the resistor and capacitor values) which affects the timing of the right hand chip, which in turn produces the raspy horn sound. But it's my first electronics course and I can't figure out any more detail than that.

Any clues? Thanks!

 

[Harald Kapp]

Both chips are astable multivibrators (amv). Google can give you thousands of hits when you search for this, so I won't repeat the description here.
The left amv has a low frequency. The right amv has a frequency in the audio range. The output of the left amv controls the frequency of the right amv.
You may want to read this.