Editing Dbx (noise reduction) (section)

===dbx I and II<span class="anchor" id="I"></span><span class="anchor" id="II"></span>===
dbx Type I system is meant to be used with professional recording media that have a signal-to-noise (S/N), before noise reduction, of at least 60&nbsp;dB and a -3&nbsp;dB frequency response of at least 30&nbsp;Hz to 15&nbsp;kHz. The system relies on the medium being fairly linear in volume and frequency response.

dbx Type-II is for more noisy media that have a lower S/N and much more restricted frequency response.  In the control signal path, the dbx Type II process rolls off the high and low-frequency response to desensitize the system to frequency response errors – since the [[roll-off]] is ''only'' in the control path, it does ''not'' affect the audible sound. The dbx Type-II "disc" setting on consumer dbx decoders adds an additional 1–3&nbsp;dB of low-frequency roll-off in both the audio path and control path. This protects the system from audible mistracking due to record warps and low-frequency rumble.

Both systems use 2:1 companding and provide exactly the same amount of noise reduction and dynamic range improvement – in other words, they provide the same end results, but are not compatible with each other.