1. Dither and Noise Shaping

2. When do we use DITHER?
Most commonly when Converting DIGITAL AUDIO BITRATES
Ex: 24bit  16bit for CD

3. What is DITHER? It is actually adding NOISE to an audio signal.
We make a trade:
A little low-level hiss is added BUT…
There is a big reduction in DISTORTION.

5. 16-Bit CD Audio Remember: 16-bit CD has a 96dB MAX dynamic rang
BUT we don’t ALWAYS listen to our music at its full dynamic range

6. More on BITS… We are using less BITS when volume level is not FULL
QUIETER digital audio has more DISTORTION because it is utilizing less of those BITS!

7. Here you can see the low bitrate

8. TRY THIS ANALOGY:
Spread your fingers and hold them up a few inches in front of one eye, and close the other. Try to read this text. Your fingers will certainly block portions of the text (the smaller the text, the more you'll be missing), making reading difficult.
Wag your hand back and forth (to and fro!) quickly. You'll be able to read all of the text easily. You'll see the blur of your hand in front of the text, but definitely an improvement over what we had before.
The blur is analogous to the noise we add in dithering. We trade off a little added noise for a much better picture of what's underneath.

9. The LSB. What is that? LSB stands for the LEAST SIGNIFICANT BIT
This is where the noise is added
It spreads individual ERRORS into NOISE

10. In other words…
Creating NOISE actually helps us hear LOW LEVEL SIGNAL BETTER!

11. So when does dither happen?
Converting Sample Rates
Mixdown of a digital project
Normalizing: What is that?

12. Your DAW
The good news is that your software usually does this automatically
Bitrate conversion often allows for the option

13. The Power of our BRAIN
Hearing through dither is like picking out a voice in a crowded room
Our brain can separate low level sound from the noise created by dither

14. In Short… Dither is INTENTIONAL Low-Level NOISE
Is used in DIGITAL SYSTEMS
It’s better than DISTORTION

15. Finally… Noise Shaping
This uses DITHER to make it SEEM like there is a lower NOISE FLOOR
This also uses the ‘Fletcher-munson’ curve: It considers how we HEAR
Again, fooling our brain into hearing something else

17. Listening examples (bottom of page):
.personal.uni-jena.de/~pfk/mpp/dither.html