What is Dithering Audio? – Why It’s Necessary

Dithering is a process which can be applied to a number of different types of media including audio. This being an audio mixing website, let’s specifically identify what is dithering audio and why it’s done.

What is Dithering Audio

Dithering audio is the process of intentionally adding low level white noise when lowering the bit depth of audio.

As I mentioned in my breakdown on what is bit depth, the bit depth setting as it relates to audio recording hardware and your digital audio workstation (DAW) refers to the amount/range of amplitudes to which every unique sample which can be assigned.

The amplitude of a sample of audio is essentially its volume which is determined by the strength of the sound pressure of that sound wave (see parts of a sound wave for more information).

When audio is recorded, every sample gets assigned a different amplitude value.

24 bit depth, the most common bit depth to record audio at, features 16777216 (2 to the 24th power) unique values it can assign to every sample.

As I explained in my overview of the noise floor, when you don’t have the exact value an amplitude requires, this results in a quantization error to where the amplitude is essentially rounded up or down to an existing nearest value. This manifests as unpleasant distortion.

When we lower the bit depth of existing audio, it makes sense that we get this distortion because we’re doing a huge amount of amplitude rounding up or down to make it work which results in a lot of quantization errors.

So why would you want to lower the bit depth of audio? Why can’t you just leave it at whatever it was recorded at?

Why Lower Bit Depth

The main reason to lower the bit depth of audio is because the medium can’t support or playback a higher bit depth.

For example, CD’s are a 16 bit audio format, so when you have 24 bit audio, it needs to be converted to 16 bits to actually be written to a CD.

Simply converting the audio to 16 bits would create all of that distortion I just mentioned. You may not always notice it, but it’s always there and is more noticeable at quiet sections and fade outs.

This is why audio mastering engineers use dithering during the process of converting 24 bit audio down to 16 bit.

What Does Dithering Do?

Getting back to what is dithering audio, I initially mentioned this is the process of intentionally adding white noise when you’re lowering the bit depth.

Dithering actually replaces the distortion from quantization errors with a smoother and more comparatively pleasing low level noise floor hiss.

You can actually shape the tone of this artifact by using different shaping options to dither with to sculpt the intentional noise and get a smoother result. All DAWs have an option to dither built in when you’re exporting audio, or you can use a third party plugin like Izotope’s Ozone.

Audio Dithering Reviewed

• Dithering audio is the process of intentionally adding low level white noise to your audio to replace the distortion of quantization errors during the process of lowering bit depth.
• Bit depth refers to the amount of amplitudes (essentially volume values) which samples can be assigned. Higher bit depth options have more values which can be assigned, yielding higher resolution and cleaner audio.
• When a sample can’t be recorded at the proper amplitude, it gets rounded up or down which results in a quantization error. This manifests as unwanted distortion.
• When audio is converted to a lower bit depth, it leads to a lot of quantization errors as amplitudes are readjusted and reassigned en masse.
• Audio dithering replaces the quantization error distortion with a pleasant and rounder white noise which manifests as an analog noise floor like hiss.
• Dithering is important when dropping bit depth from 24 bit to 16 bit (as in getting audio ready to print to CD, for example) to keep audio from distorting.