Dithering could be the most misunderstood topic when mixing and mastering. Dither is the low-level noise added to digital audio files intentionally when rendered to a lower bit depth. Although it might seem to be counterintuitive, the process is remarkably effective.
Dither masks the quantization distortion that generates artifacts and unwanted noise in digital audio. When you transform a mix through an ADC (analog-to-digital converter), the signal gets digitally represented in binary code.
The ADC takes samples at specific rates and sizes to govern how much gets captured. You must have a sampling rate equal to or up to double the highest audio frequency to get a positive result.
What Is quantization distortion?
You have a 24-bit audio file. What you’re working on requires that information be available in 16-bit resolution. When you initiate the command to remove those eight bits, the software must round out the data to fit your new structures.
That process is called quantization. Since that creates fewer steps for mapping the amplitude levels of the audio, an error occurs that makes unwanted low-level noise that impacts the listening experience.
Although the music masks it when enough bits are available, you can still pick it up at the 16-bit level during quiet passages or during fades. Even if you cannot hear the distortion itself, the sound tends to be harsher and unrealistic, making it less enjoyable for listening.
Dither helps to solve the distortion issue
You can save a file from a lower sampling rate and the quantization distortion by adding dither. It masks the unwanted audio through decorrelation, making the mapping process more randomized to make it harder for the average listener to discern the change. You receive a steady, analog-style hiss in the file at a low level instead.
This technique is sometimes included in the noise-shaping menu of DAWs, plugins, and music software. It allows you to change the frequency characteristics of the added noise to ensure it falls into the least audible range.
When should I use dithering in my mixes?
The easiest way to think about dithering is to look at the bit depth of your mix. If your work is going down, you should add it. Even if you’re not hitting 16-bit, this technique can improve the quality of your work.
When you switch between data compression codecs, dithering isn’t necessary. AAC, MP3, and others introduce signal artifacts that dither cannot remedy.
That means your best option is to use the highest bit rate possible while having a file size that meets the standards of your preferred streaming platform.
The one mistake that many musicians and audio engineers make at first is to add dithering too soon in the processing chain. It should be the last step, which means a processor shouldn’t get inserted into your audio editor or DAW after it.
Most software options have a basic automatic dithering option as a default that handles the most severe issues. When you want more noise-shaping options for your mix, consider adding dither for each lower conversion.
