Thread: removing unwanted "wiggle" from sine wave

Hi,

Please see attachments.

Is it possible to derive the equation for the "wiggle" (green wave) given the wiggle's amplitude and period as shown?

Or are there any suggestions as to how I might reach my ultimate goal, which is to derive the equation for the red wave?


(I know, I know, this should go in the Physics Help Forum Waves page--But I had problems uploading my thumbnails there, whereas here everything works smoothly.)

Thanks

You seem to have some excellent s/w at your fingertips: have you tried fourier analysis?

Originally Posted by Matt Westwood

You seem to have some excellent s/w at your fingertips: have you tried fourier analysis?

Not all that excellent--just "advanced grapher." Does not handle fourier analysis.

Anyways, that's part of my problem here. Fourier analysis is over my head.

Would you say that FA could be useful in this case?

I confess that the details of Fourier analysis are somewhat out of my immediate reach as well nowadays (I used to know, I'm rusty now).

What it does is separate out a more-or-less complicated (but periodic) function into a sum of sine waves of various frequencies. In this case I wouldn't dream of doing it analytically, but there do exist tools which do it automatically. I used to use one many many years ago written in Fortran for analysing the pitch, roll and yaw of ships in heavy seas. I'd be very surprised if there isn't some free program out there somewhere that would do the job for you - but I've not been able to find one with a bit of cursory googling.

It's obviously a practical problem (you have some unwanted harmonics on a signal that ought to be a pure sine wave). Here's a link that may help, apologies if it's over your head, it's heavy going.

Originally Posted by Matt Westwood

It's obviously a practical problem (you have some unwanted harmonics on a signal that ought to be a pure sine wave). Here's a link that may help, apologies if it's over your head, it's heavy going.

Ok, thanks for orienting me a bit. I look forward to checking out the link you mentioned. However I don't see it. Could you please repost the link?

Thanks

Fast Fourier transform - Wikipedia, the free encyclopedia

Sorry.