There are some topics out there that never fail to get engineers ranting and raving. You know, topics like loudness, compression, mastering and…
Dithering.
Dithering could be an intimidating subject—it has a lot to do with the fundamentals of digital audio.
However, applying dither correctly is extremely easy and simple to get more listeners. Once what you are doing and why you are doing it, you will never have to stress about whether to dither or not again.
What’s dithering?
Dither is low-level noise added to your audio to reduce errors when changing bit depth.
I understanđ what you are thinking, “how could including noise make my recordings sound better? Is not noise a bad thing?”
Dither is not just an audio term—and the noise it adds is really more like random variation.
Actually, the word dither means “nervous vibration.” It comes from how it was found.
Engineers discovered that mechanical aircraft computers performed more accurately in flight than on the ground.
The vibration from the plane’s engine actually helped enhance the accuracy of the sticky transferring components within the machines.
The noise that dithering provides to your tracks works the same method. It helps improve the accuracy of your digital audio information.
When should you dither?
Before we get too far into the nuts and bolts, let’s begin with the best practices.
Follow these three tips and dithering will not cause you any trouble:
- Do not change file types unless you absolutely have to. When you tracked at 24-bit/44.1kHz, just stay there! If for some reason you should downsample, make sure you dither during conversion.
- Save dithering for when your files are headed outside of your DAW. Dither only once—during export.
- When you are sending your files for mastering, leave dithering out if you could export 32-bit float files. In this case, the mastering process will take care of dither for you. If you export anything other than 32-bit float, you must dither. That features once you bounce files which are the same bit-depth as the ones you recorded.
That’s it! When you never want to think about dither again you could stop right here and get back to your newest project. However, when you are still confused, or if you wish to know why you need to follow these rules, read on.
I will go through everything you ever needed to know about dither but were afraid to ask.
Bit-depth
Let’s begin initially. We are talking about digital audio here!
The files your pc makes when you record are digital representations of the analog signals made by whatever you plug into your audio interface.
Before you begin recording, you must select a sample rate and bit-depth for your DAW session. When you choose the bit depth, you are truly selecting the accuracy of the files you make during recording.
Each additional bit increases the resolution that your ADC (analog-to-digital converter) has to measure the level of an incoming signal.
That is why we suggest you record 24-bit files for LANDR mastering. They are the best option available in most DAWs.
Reducing the effects of error
When your files are in your DAW, lowering the resolution is difficult. Reducing the bit depth will introduce digital error when you aren’t careful.
However, you will need to do it at some point in your process. Here’s why…
Your DAW makes the calculations that energy your faders, busses, and plugins at a higher resolution than your audio files.
That means that unless you are exporting your files in 32-bit float, you will be decreasing the resolution of your tracks once they leave your DAW—and introducing error!
Error in your digital files has real-world consequences for how your tracks sound. It could translate into harsh noise and distortion.
This distortion only occurs in the quietest part of your system’s dynamic range, however, proper dithering fixes it!
Visualizing error
To see what I mean, let’s see what error looks like in a picture, which is just another type of digital file.
- The picture on the left is the original. It’s just like the file you recorded into your DAW at full resolution.
- The center one is like taking these pristine files and dramatically decreasing their bit depth. It’s pretty hard to recognize the picture.
- The one on the right has been reduced the same amount, however, this time with dither utilized.
It looks a lot better! However, how could dither make a low-resolution picture look better?
Once we reduced the resolution, we had to throw out lots of the information in the file that allowed us to see the detail.
How that info gets thrown out is why dithering is vital. Keeping the errors to a minimum has a huge impact.
Let’s take a look at exactly what occurs when bit-depth reduction gets rid of info in your audio files.
Rounding and truncating
Imagine we have to change 24-bit files into 16-bit ones. To make them fit, all the information from the original 24-bit files has to go into the 16-bit spaces.
Meaning something has to get left behind. However, how could you do the least damage?
The first option is to easily cut the numbers off to make them fit. That is known as truncation and it’s the least accurate method of solving the issue.
Instead of just cutting the numbers off, we could attempt rounding them up or right down to get nearer to representing the 24-bit audio in 16-bits.
However what occurs when the quantity you have to spherical is true within the center? You can attempt a rule of thumb—say you decide to round up every time you encounter a number right in the middle.
This way at least you will be correct some of the time. The trade-off is that you will be wrong just as often! That is known as rounding error.
The noise (or random variation) that dither includes essentially randomizes the decision to round up or down.
After dithering, the distortion that will be made by truncation or rounding has a much less detectable impact.
Dithering Heights
All this business with rounding and error might seem completely academic, however, correct dithering could make a difference in your last product.
At the very least, including dither at the correct point in your project is the closest thing you could get to enhance your mix with one click on, even when it’s just a small improvement.
As an engineer, you need to strive for the best possible sound you could—and not miss any chance to make it better.
Now that your method around dither, get back to your DAW and bounce some tracks.