I read Cobb Tuning’s Facebook postings and saw the following the other day:  http://www.cobbtuning.com/subaru-knock-monitoring-and-dit-knock-logic-changes/

Most people that have turbocharged Subarus and either have a Cobb Accessport or want one always ask how does one monitor for knock.  I’ve elaborated on this in the past (here) but the information in the link comes straight from the source!

Excerpt:

Detonation events are inevitable and will occur from time to time on any modern vehicle running on pump gas.  Your car is built to recognize these events and take the appropriate action to defend against them causing any damage.  The Subaru knock detection system tends to err on the side of caution.  This makes it common to see “false knock.”  False knock occurs when the ECU corrects for a knock event but the noise registered is due to other noises that aren’t necessarily detonation or harmful to the engine.  This often happens accelerating from a stop while letting the clutch out, during gear shifts (more so if grunting while shifting), accelerating at low RPM in a high gear, under cruise on the freeway, and during abrupt throttle changes.

Read the rest at the above hyperlink.  Enjoy!