Bit Depth and Noise Floor

Bit depth sets the quantisation noise floor, and therefore how quiet a soft passage can stay.

Related

Bit DepthNoise FloorDither

The problem

Bit depth sets the level of quantisation noise, and therefore how quiet a soft passage can stay. The difference between 24 and 16 bits is not clarity but silence and headroom.

Signal chain

The converter cuts the analogue voltage into discrete steps; finer steps mean smaller quantisation error. The error spreads across the high frequencies and sounds like a very light hiss, which takes up a larger share as the signal gets quieter.

Placement and settings

Record at 24 bits with peaks between -12 and -6 dBFS to leave room for surprises. Mix internally at 32-bit float, then reduce to 16 bits with dither for the master. Do not make large fader moves in a 16-bit project; the noise floor rises with them.

What to listen for

Find a very soft piano tail and raise the monitor until it is just audible: a 24-bit take stays clean until the tail vanishes, while a 16-bit take shows a faint grain. Then lift the same passage by 20 dB and hear whether the noise floor arrives first.

Common misconceptions

• 24 bits sound clearer → they lower the noise floor, not the distortion.
• Float lets you push anything → it prevents clipping, not noise.
• Dither is optional → without it, soft passages break up when reduced to 16 bits.

Sources

• Lipshitz, Wannamaker and Vanderkooy, Quantization and Dither, JAES
• AES Convention paper on bit-depth audibility in quiet passages

Used for fact-checking only; all prose is original.