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Eric Altizer

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I have made several recordings of late and exported them to wav 24/44100
with the dithering set to triangle. Can someone tell me what this means? I was wondering if I need to re-do the recordings now with the dithering set to "none". The other dithering options are: rectangle, triangle, shaped and none. I am trying to figure out what this means. :confused:
 
Dithering is no more than simply adding a noise floor to a recording. This is because at the quietest points in your sound file (we're talking like the end of a fade out at, say, -80 dB) your actual waveform is not as accurately reproduced because it is not, for example, utilizing every one of your sixteen bits. Thus your lowest-amplitude waves will sound choppy or distorted. Adding the noise floor both fills in the gaps in those choppy spots and in some cases boosts the overall signal enough that you better utilize that quietest bit. This lends to a "smoother" sounding fade-out, for example.

I imagine that your selectable attributes like "triangle" or "rectangle" may refer to the equation used to calculate the waveform for noise. I have seen references to a "triangular probability density function", which is used in calculating your dithering noise. However, I have no idea how to explain the origin of this name as I am not a statistician.

A more homely guess would be that you can generate different types of white noise for your noise floor, and the "shapes" you are selecting might be wave shapes (e.g. "triangle" means you generate a sawtooth waveform, or "rectangle" generates a square wave). But, that's just a guess.

Here's a link to a page a Middle Tennessee State University. I hear they have a mighty good recording arts degree program.

http://www.mtsu.edu/~dsmitche/rim420/reading/rim420_Dither.html
 
Haha! Sorry, I forgot to mention this in my first post, and it's pretty fricking relevant. If you are exporting to 24-bit, you really don't need to dither. If you plan on going to redbook CD (standard 16/44.1k) you will want to dither when you cut down on your wordlength.

The reason: 16 bits of wordlength give you 65,536 possible values. Since sound waves consist of both compression AND rarification (postive AND negative air pressure), that gives you roughly 32,768 levels of amplitude in each direction (positive and negative), excluding a "zero" value.

24 bits gives you 16,777,216 possible values, 8,388,608 in each direction (excluding zero).

You can see how much more accurate 24-bit recording is. And, in fact, it is accurate enough that you don't have to dither because your ears aren't really good enough to hear the bad quantization (distorted crappy sounds at low levels) with 24 bits. That being said, if you are just exporting to 24 bits, then just turn your dithering off.


By the way, I only learned this stuff from taking a college class in electroacoustic composition (we had to learn quite a bit about our equipment). That was over a year ago, and so some of it might be a little rusty. If anyone can correct me on anything, please do so in the hopes that any poor advice from me won't destroy Eric's pristine audio recordings.

Cheers,

~Brent
 
Thanks for that response. I use Audacity for sound editing and the "triangle" setting may just be a default setting but I am not certain. Since this is an archiving project of open reel to digital transfers I prefer to leave the transfers unprocessed. I am not even cleaning them yet. Thus I am thinking that I will set the dithering to "none" for now and hopefully that will be just fine for what I am doing. Does this make sense?
 
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Yeah...especially since you are archiving.

Adding anything (dither, effects, eq) now would be a no-no because you can do just about anything after the fact--but once you archive it you only have the one copy or version. Once done you can't "undo" a dither without re-digitizing the tape and starting with a "new oroginal source"...and, of course, if it were the case that you felt you could preserve the reels, you wouldn't be archiving now, would you?

So NO! Don't add any dither! Haha, hope that helps.
 
As for the earlier recordings that were processed on the triangular dither I am still uncertain how they were effected and if I need to re-record them or not. I don't think that I can here any difference. I have tried the different dithering settings in real time.
 
Depending on how much time you put into transferring the recordings to digital, it might not be worth it to re-record them. The only effect would be a noise floor--and a tiny one at that--sort of like tape hiss. I think the only time this could be a problem is if you keep dithering over and over again...you'll just get hiss building up by the layer.

If you can't hear it, and it doesn't bother you, I don't think I'd worry about it. But, if you can hook your reels up, set your levels, hit record, and go watch TV while the tapes run, what's the harm (except for disk space)?

Word.
 
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