NES's noise channel

Discuss NSF files, FamiTracker, MML tools, or anything else related to NES music.

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CKY-2K/Clay Man
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NES's noise channel

Post by CKY-2K/Clay Man » Thu Feb 07, 2008 12:32 pm

Okay. It's obvious that the noise channel being a white noise channel is full of sh. The noise channel, when I view the wave looks like a square wave with patterned randomized pulse widths.

I looked at wikipedia's refference of how it works:
http://en.wikipedia.org/wiki/Linear_fee ... t_register

It makes a lot of sense now when I saw that, so tell me if I'm right when I discribe it.

The noise channel has a register that discribes the shape of the wave.
The binary is the amplitude, so it would look like this:

examples

1 0 1 0
_ ¯ _ ¯

1 1 0 1
_ _ ¯ _

And there are multiple bits put into a pattern. The 2 modes in the noise channel are switches between the 2 patterns that NES has.

The pitch describes how fast it cycles through the pattern.
Image
Here to at least get an idea of how the NES works. I mean I know alot of the basic things, but this place'll help me grasp more how NES functions.
Major respect to NES developers.

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blargg
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Post by blargg » Thu Feb 07, 2008 1:24 pm

You've got the general idea. Here's the full long noise sequence, all 32767 bits of it:
Image

CKY-2K/Clay Man
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Post by CKY-2K/Clay Man » Thu Feb 07, 2008 6:39 pm

Wow I didn't think it would be that long.

Well the obvious difference between the noise channel and white noise is that white noise has random amplitudes for the wave, but the NES noise channel is just a 1-bit amplitude.
Image
Here to at least get an idea of how the NES works. I mean I know alot of the basic things, but this place'll help me grasp more how NES functions.
Major respect to NES developers.

johannesmutlu
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Joined: Fri Mar 11, 2011 2:22 pm

Re:

Post by johannesmutlu » Sun Nov 18, 2012 2:53 pm

CKY-2K/Clay Man wrote:Wow I didn't think it would be that long.

Well the obvious difference between the noise channel and white noise is that white noise has random amplitudes for the wave, but the NES noise channel is just a 1-bit amplitude.
speaking about the nes noise channel i have discovered that the noise channel can do realistic sound effects like explosions,fire drums,water etc,,,
i was wondering how that could,ve be ever possible.
i remember hearing many nes & gameboy games with many sound effects wich almost sounded like real,i was mind blown away for nearly 2 dekages, like when bowser spits fire out of his mouth in mario 1,when the turtles use their sword in turtles 1,when wario in warioland 1 uses fire wario or jump in the water,those explosions sounds from throwing or hitting barrels in the donkeykong land series etc,,,,also some square waves can produce realistic like sound effects like those cannon and bomb sound effects in supermariobros 1 & 3 or those explosion sounds in journey to cilius all concisting out of square waves.i readed on wiki that somehow if you mix a noise channel with a tone/square wave channel,then altering the volume,so you can create a pcm file but it require more horse power,interestingly a study group suceeded to convert a pcm file into psg sound will still retaining realistic sound,now who had ever tout that creating realistic soundeffect become possible by only using fm sound? i couuld,ve only dream & fantesize about it for years!!!

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rainwarrior
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Re: NES's noise channel

Post by rainwarrior » Sun Nov 18, 2012 4:42 pm

At the highest frequencies, the noise channel is effectively putting out random amplitudes since it is well above audio frequency range (see: pulse width modulation), so it's not really that far from white noise in that range. At lower frequencies though it is a lot different than white noise, the spectrum above the operating frequency becomes harmonic.

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