How To

Wave Generation

McPepic 2024-02-01 20:06 (Edited)

I'm working on an audio-based project and was curious how some of the data is interpreted to form the resulting audio wave.

I'm using a triangle wave and need to recreate the wave given the pitch, pulse width, and volume so that I can sample values from it.

Does anyone know how to create a mathematical expression to create the wave based on the pitch, volume, and pulse width of a triangle wave?

SP4CEBAR 2024-02-01 22:26

I think I know what this is for, Good luck!

McPepic 2024-02-02 16:36

Wait, pulse width only works with square waves?

SP4CEBAR 2024-02-02 23:42

Yes

McPepic 2024-02-02 23:46

I'm going to need to rethink this a bit. I really don't mess with audio on LowRes.

SP4CEBAR 2024-02-03 10:15

If you listen to this frequency sweep
https://lowresnx.inutilis.com/topic.php?id=1890
Without touching the screen, you'll be able to hear some artifacts that may give some information about the bit depth of the audio.

SP4CEBAR 2024-02-03 13:01

@McPepic, I think this is what you are looking for:
https://github.com/timoinutilis/lowres-nx/blob/master/core/machine/audio_chip.c

SP4CEBAR 2024-02-04 16:14 (Edited)

Wait, you wanted a mathematical expression these waveforms in general (not the specific NX sounds), I can give you some:

• noise: spam some math functions like sine waves of different amplitudes and frequencies until it sounds random-ish.

For the other waves, here are a few approaches that could work:

• approach 1: integers
  • square: Y=int(x*2)-2*int(x) (similar to X- X mod 2)
  • triangle: Y=|1-2*X|-2*int(x)
  • sawtooth: Y=x-int(x)
• approach 2: domain: u = X-int(x)
  • square: y=int(2*u)
  • triangle: y=|1-2*u|
  • sawtooth: y=u
• approach 3: sine
  • square: sin(x)>=0
  • triangle: y=asin(sin(x))
  • sawtooth: y=atan(tan(x))

McPepic 2024-02-05 01:37

Alright, thanks! I'll look into these for the project. God bless you!

SP4CEBAR 2024-02-05 09:46

God bless you too man!