This sound file was recorded with a PLEX KNOCK MONITOR
It is an engine running at 3000rpm (without knocking) and every 5 seconds we change the PLEX KNOCK MONITOR filters as following:

0-5 sec: no filter
5-10sec: 5KHz filter
10-15 sec : 6KHz filter
15-20 sec: 7KHz filter
20-25 sec: 8KHz filter
25-30 sec: 9KHz filter
30-35 sec: 5KHz high-pass filter
35-40 sec: 10KHz high-pass filter

Dyno-run at 3000rpm (steady)/Knock Filter changing every 5 sec

This is a typical dynorun that produces a mild knocking event and is recorded without a knock filter

PLEX TUNING