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Dithering Audio [How it Works. Explained]

Changing of high-resolution audio to CD quality causes the distortions. Dithering is popular way to reduce impact of the artifacts to sound quality. Read in the article what happens there and how it can be fixed. Keep reading.
 
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Author: Yuri Korzunov,
Audiophile Inventory's developer with 25+ year experience in digital signal processing,
author of the articles that make audio easy for beginners

Audio Basis - articles about audio

Sometimes you need to adjust an audio file for a device or music format with CD quality (16-bit/44.1 kHz). It adds distortions due to information losses. These losses are not ordinary white noise. They as correlate with the music. It can cause additional listening discomfort. And there is technology that can partially solve the issue.

 

What is audio dithering?

Dithering audio is a suppression method of non-linear audio distortions when bit depth is decreased. It is adding specially generated very weak noise to a digital signal. The dithering algorithm of AuI ConverteR 48x44 (alphaD) observes the signal behavior. It allows for minimizing noise influence on hearing and open minute details of a music.

We will not tell you about dithering mathematics. You can read it at another place. We'll just show what you get.

Dithering audio

 

 

When should you use dither?

Dithering is optional processing. If you use it, make sound check for better result. Dithering is most effective for music with low loudness. We should refer loudness relative maximum loudness of used resolution. In instance, the maximum loudness of 16 bit resolution is about 32000. The minimum is 0. You can follow your own perception when choose control level. It may be the quietest place of tested recording.

 

Now we make 24-bit to 16-bit conversion without dithering. When 24-bit signal truncated to 16-bit one, rounding to thr nearest integer is doing.

Pure sine after 24-bit to 16-bit truncation

Pure sine after 24-bit to 16-bit truncation. Appear non-linear distortions

We see in this picture non-linear distortions ("wood of blue sticks"). Middle level of peaks of the "sticks" is about -135 dB.

Levels of these distortions increase and decrease together with the useful signal. In ther words, the distortions correlate with the useful signal.

No signal = No these distortions

The "digital sounding" is consequence of these "sticks" and their correlation with useful signal. And it is not "not very pleasant".

 

Case #1: without dithering

You have 24-bit or 32-bit (integer or float point) source. You need 16-bit source.

 

Pure modeled sine signal 24-bit or 32-bit (float point also)


Pure modeled sine signal 24-bit or 32-bit (float point also)

 

Case #2: with dithering audio

Now we will see 24-bit to 16-bit conversion with Audiophile Inventory's dithering audio alphaD.

In settings of AuI ConverteR 48x44 we set minimal value (Light) of Dithering mask depth... slider

Dithering audio settings of AuI ConverteR 48x44 - Light

Dithering audio settings of AuI ConverteR 48x44 - Light value (recommended)

That is result of 24 to 16 bit conversion

Conversion 24 to 16 bit with dithering

Conversion 24 to 16 bit with AuI's dithering audio alphaD

Now we see 2 things:

1. Mid level of peaks of noise about -145 dB.

2. The noise does not depend on the behavior of the signal. Now we loss "digital sounding".

If necessary we can add dithering intensivity for mask non-linear distortions by moving of Dithering mask depth... slider to right.

 

Attention!!! Non-traditional case!

Let's look to generated without dithering source 16-bit sine.

Source 16-bit sine generated without dithering

Source 16-bit sine generated without dithering

"Wood of sticks" again :)

Below we will see how does slider Dithering mask depth... position to signal spectrum. How it mask the non-linear distortions.

Source 16-bit sine generated without dithering after dithering level 0
Source 16-bit sine generated without dithering after dithering level 1
Source 16-bit sine generated without dithering after dithering level 2
Source 16-bit sine generated without dithering after dithering level 3
Source 16-bit sine generated without dithering after dithering level 4
Source 16-bit sine generated without dithering after dithering level 5
Source 16-bit sine generated without dithering after dithering level 6
Source 16-bit sine generated without dithering after dithering level 7
Source 16-bit sine generated without dithering after dithering level 8
Source 16-bit sine generated without dithering after dithering level 9


We can mask source non-linear distortions with changing Dithering mask depth... slider position.

 

Watch: Demonstration of sound distortions without dithering for 8-bit signal
video: Demonstration of sound distortions without dithering for 8-bit signal
 

 

Watch: Andrey Subbotin talks about dither (en sub)

 

video: Andrey Subbotin talks about dither (en sub)
 

 

 

AuI ConverteR's alphaD dithering

Audio file converter AuI ConverteR provides own dithering technology alphaD. The method smooth "16-bit artefects" and keep low noise.

It supported in all version of the program.

In configurable Modula-R edition, dithering is provided by "Base (core)" module.

 

How to apply dithering with AuI ConverteR?

To apply dithering with AuI ConverteR:

  1. Launch AuI ConverteR software
     

     
  2. In the main window, push Open files button and select source files.
  3. In the main window, check Dither button (led is light).
     
    AuI ConverteR Dithering
     
  4. Push Start button and wait for the end of the conversion.

WARNING: For bit depth above 24 bit and DSD on input and output, button state is ignored.

If you need, change dithering settings in the converter's Settings > General tab.

 

Conclusions

  1. Dithering allows getting more "transparent" sounding without "16-bit digital artefacts".
     
  2. However, the dithering increases average noise level due to the artefact's enetrgy is distributed over frequency band of signal.
     
  3. In common case recommended use Light position of slider Dithering mask depth... in Settings windows of AuI ConverteR 48x44.
     
  4. We can mask non-linear distortions of 16-bit sources with moving slider Dithering mask depth... to 3 or 4 position (from left).

 

 

Frequently Asked Questions

What is dithering used for?

The audio dithering is used to smooth non-linear distortions in 16-bit resolution.
See more...

 

Why is dithering important?

The audio dithering is important because it allow significantly eliminate resolution-decreasing losses.
See more...

 

 

Read more

  1. What is Jitter in Audio. Sound Quality Issues >
  2. 64-bit audio processing. Necessity or redundancy >
  3. How to Choose the Best Audio Converter Software >
  4. What Is Ringing Audio >
  5. Bit-Depth Audio and Harmonic Distortions >
  6. Audio as Optics >
  7. What is optimization audio for DAC >
  8. Where is the Limit of Audio Quality? >
  9. Power Conditioner for Audio. It's real advantage? >

 

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