It is a tiny bit of deliberate noise added on purpose to hide worse-sounding rounding errors.
Same wave, same bit grid: no dither locks rounding error to the signal (crackle); dither randomises it into a soft, steady hiss.
What it is
Tiny deliberate random noise added before reducing bit depth, so rounding errors sound like soft hiss instead of crackly distortion.
Key facts
Bit depth sets the number of loudness steps: 16-bit = 65,536 levels, 24-bit = 16,777,216 levels, 8-bit = only 256 levels.
Dynamic range per bit: each bit adds about 6.02 dB. 16-bit = ~96 dB, 24-bit = ~144 dB, 8-bit = ~48 dB.
Quantisation error = the gap between the true value and the nearest step; without dither it correlates with the signal and becomes audible distortion.
Dither decorrelates that error: it turns harsh harmonic distortion into a constant, benign noise floor.
TPDF (Triangular Probability Density Function) dither is the studio default: 2 LSB peak-to-peak, flat across frequency, no noise modulation.
Dither only matters at the FINAL bit-depth reduction (e.g. 24-bit mix bounced to 16-bit). Dither ONCE, last.
Noise shaping pushes dither energy up to 15-20 kHz (where ears are less sensitive), giving ~6-18 dB lower PERCEIVED noise.
CD standard = 16-bit / 44.1 kHz, the classic place you must dither. LSB = Least Significant Bit = smallest level step.
Theoretical noise floor of 16-bit dithered audio sits around -93 dBFS RMS (dBFS = decibels relative to full scale).
Rule: never dither twice, never dither a 24-bit-or-deeper export, never normalise after dithering.
How it works
Audio lives at high bit depth (e.g. 24-bit) with millions of loudness steps.
Reducing to fewer bits (16-bit) forces each sample to round to the nearest coarser step.
Without dither, that rounding error follows the signal and sounds like crackle on quiet fades.
Dither adds faint random noise BEFORE the round so the error becomes random, not patterned.
The rounded result now has a smooth, steady low-level hiss instead of distortion.
Optional noise shaping moves that hiss into high frequencies your ears barely notice.
Real examples
Bouncing a finished 24-bit mix down to a 16-bit WAV for a CD master: switch dither ON.
A song with a long quiet fade-out to silence: dither keeps the tail smooth instead of grainy.
Exporting a podcast or audiobook to 16-bit for distribution: apply TPDF dither on the final render.
Solo piano or acoustic guitar with lots of quiet decay: most obvious place dither saves the sound.
Game/sample library trimming 24-bit captures to 16-bit assets: dither each final reduction once.
How it helps in live sound
Recording live to a 24-bit interface? Keep it 24-bit end to end. NO dither needed until final export.
Only dither the very last step: the 16-bit file you hand to the client or upload.
In your DAW (Reaper/Pro Tools/Ableton) tick 'Dither' in the render/bounce dialog, pick TPDF.
Add noise shaping only for 16-bit masters meant for listening, not for files going to more processing.
Streaming/podcast at 24-bit or higher? Leave dither OFF, it is pointless and just adds noise.
If you hear gritty crackle on quiet fade tails after a bounce, you forgot to dither, redo the export.
Everyday analogy
Like gently shaking a photo while scanning it so harsh stair-step edges blur into a smooth gradient your eye reads as continuous.
Watch out
Myth: dither makes audio cleaner so always use it. Truth: it ADDS a little noise on purpose, and you only apply it ONCE at the final bit-depth reduction, never to 24-bit or twice.
Fun fact
Adding the right random noise can make a dithered 16-bit signal resolve detail QUIETER than its own LSB, around -110 dBFS, below the level a single bit can represent.
Key takeaways
Dither = deliberate tiny noise added before rounding to a lower bit depth.
It swaps ugly signal-locked distortion for a gentle, steady, far less noticeable hiss.
Use TPDF dither, applied ONCE, only at the final reduction (e.g. 24-bit to 16-bit).
Never dither 24-bit exports, never dither twice, never process after dithering.
Each bit = ~6 dB of dynamic range; 16-bit = ~96 dB, the classic CD target.