DIY Audio Knock Sensor – How To
May 17, 2024It is possible to listen engine knock relatively easily and for less than a few dollars. This DIY audio knock monitoring guide has two parts. The first part deals with the hardware, how we actually get a signal from our engine. The second part deals with the software that filters out the unwanted frequencies and allows us to listen to engine knock is close to real time. This guide details the whole process.
Hardware
By connecting a 3.5mm headphone jack to a knock sensor and running it to the mic input on a laptop we can monitor engine noise is close to real time with the help of some free software.
Parts Needed
Audio Extension Cable and Jack
- 3.5mm Stereo Jack (Male, Bare) – Cut the end off a stereo mic or some old headphones (or source a bare jack from an electrical supplier).
- 20cm or so of stereo headphone cable (to connect 3.5mm jack to knock sensor connector)
- 3.5mm Female-Male, Stereo Extension Cable (3-5 meters) – Run cable from knock sensor to laptop inside the vehicle. This wire goes between the knock sensor and your laptop.
- Knock Sensor
- Knock Sensor Pigtail/Female Connector (or buy a connector kit to make your own). Wire this to the 3.5mm jack from above. Use the extension cable to run the wire into the car and into the laptop mic socket.
- Headphones
- Laptop
Software
VLC Player – To listen to mic input in close to realtime. Latency will depend on laptop.
APO Equaliser – Filter out mic frequencies not in our knock frequency window
How To
Connect the bare 3.5mm male stereo jack to the 20cm headphone cable. Google “3.5mm stereo jack wiring” if you need to.
Connect other end of 20cm cable to knock sensor female connector.
Install knock sensor on engine, on engine block or cylinder head.
Install knock connector cable (made above) onto knock sensor. Connect 3.5mm extension cable (female end) to knock sensor. Run male end of extension cable into the cabin.
With all the parts connected (knock sensor to jack to extension cable to laptop mic input. Connect headphones to laptop).
Install VLC Player. Select Capture in VLC media player, choose the relevant inputs and outputs. Press Play.
Install APO Equaliser. Open APO Equaliser. Create window for mic input (knock sensor signal). Reduce volume of all frequencies outside of knock frequency window.
You should now be listening to the knock sensor signal in your headphones (there may be some delay/latency between the sound and hearing it).
Demo – DIY Audio Knock Monitoring System
This video is a demonstration of what is achievable with this audio knock listening setup.
If you would like automated engine knock detection with a visual indication and/or a signal to indicate knock for an engine ECU, water injection etc, check out the MoviChip KSC
Engine Knock Detection System – KSC3
Engine Knock Detection System – The KSC3 Monitos engine knock severity in real-time, visually and/or via a 0-5v signal to engine ECU/datalogger
What Is The KSC3?
A suppl…
