Phantom harmonics? -Sound Forge - PC - MAGIX Community Forums Archive

Subject:Phantom harmonics? Posted by: sucram Date:3/6/2013 2:32:45 PM Hello all, I'm using SF 8 on a Win XP machine. I was creating test tones using SF's simple synthesis tool and viewing results in the spectrum analyzer. Sine waves look great. Triangle waves look as expected, too. But when I created a 5 second square wave at 200 hz, I see harmonics at 100 hz and octaves above that. I tested it at 1000 hz, and again, I see harmonics every 100 hz throughout the spectrum. It's with Blackman-Harris, which gives the cleanest peaks on sine waves. First, why is energy created lower than the fundamental using this digital synthesis? Second, should it be there, or is it some kind of artifact? Tanks in advance, Marcus
Subject:RE: Phantom harmonics? Reply by: ChristoC Date:3/6/2013 3:06:52 PM That is expected. It is because square waves are a rich source of harmonics; from memory, probably the richest! The short answer is find a book about Fourier Analysis, or read http://en.wikipedia.org/wiki/Fourier_analysis for a 'simple' introduction!
Subject:RE: Phantom harmonics? Reply by: musicvid10 Date:3/6/2013 8:53:41 PM "First, why is energy created lower than the fundamental using this digital synthesis? Second, should it be there, or is it some kind of artifact?" It's called the combination tone phenomenon. Two much-higher harmonics at close frequencies beat against each other to create "phantom" combination tones that can be much lower than the fundamental. With two tuneable HF oscillators and tiny piezoelectric speakers you can create near-subsonic effects that will put any subwoofer system to shame and have the neighbors calling 911. Unfortunately, no one has developed algorithms to make this response anywhere near linear and free of gargantuan artifacts in an acoustic space. If someone could, they would make a billion dollars off the patent alone. There are some good books on the physics of acoustics out there. It's all comprehensible math and waveforms, but starts to get hairy when you get into beat frequency generation and enharmonic overtones. Message last edited on3/7/2013 9:10:06 AM bymusicvid10.

Subject:Phantom harmonics?

Posted by: sucram

Date:3/6/2013 2:32:45 PM

Hello all,

I'm using SF 8 on a Win XP machine. I was creating test tones using SF's simple synthesis tool and viewing results in the spectrum analyzer. Sine waves look great. Triangle waves look as expected, too. But when I created a 5 second square wave at 200 hz, I see harmonics at 100 hz and octaves above that. I tested it at 1000 hz, and again, I see harmonics every 100 hz throughout the spectrum. It's with Blackman-Harris, which gives the cleanest peaks on sine waves.

First, why is energy created lower than the fundamental using this digital synthesis? Second, should it be there, or is it some kind of artifact?

Tanks in advance,
Marcus

Subject:RE: Phantom harmonics?

Reply by: ChristoC

Date:3/6/2013 3:06:52 PM

That is expected. It is because square waves are a rich source of harmonics; from memory, probably the richest!
The short answer is find a book about Fourier Analysis, or read http://en.wikipedia.org/wiki/Fourier_analysis for a 'simple' introduction!

Subject:RE: Phantom harmonics?

Reply by: musicvid10

Date:3/6/2013 8:53:41 PM

"First, why is energy created lower than the fundamental using this digital synthesis? Second, should it be there, or is it some kind of artifact?"

It's called the combination tone phenomenon. Two much-higher harmonics at close frequencies beat against each other to create "phantom" combination tones that can be much lower than the fundamental. With two tuneable HF oscillators and tiny piezoelectric speakers you can create near-subsonic effects that will put any subwoofer system to shame and have the neighbors calling 911.

Unfortunately, no one has developed algorithms to make this response anywhere near linear and free of gargantuan artifacts in an acoustic space. If someone could, they would make a billion dollars off the patent alone.

There are some good books on the physics of acoustics out there. It's all comprehensible math and waveforms, but starts to get hairy when you get into beat frequency generation and enharmonic overtones.

Message last edited on3/7/2013 9:10:06 AM bymusicvid10.