DIY Audio knock monitor - Am I hearing knock?

I'm still fairly new to this, I know what knock is supposed to sound like, but I don't know that I've ever heard it for myself

I built myself nice little kit for $50. Knock sensor, small amplifier and headphones.

To test it out, I bolted the sensor onto the intake manifold on my girlfriends '04 Forester. I know that's not a great place for it. But I was just testing that it worked and I could hear things, I wasn't actually trying to do anything except test my monitor.

Started the engine up, and ran it and I could hear nicely, diy knock monitor is working perfectly!

But when I drove the car, and I went to WOT, after around 5k I could hear a really sharp 'crackle' that really stood out from all the other sounds. Is that knock? It wasn't a constant sound, it was just a sudden momentary sound that happened a few times after the engine was over ~5k.

Hello it most likely was knock the Subaru is the perfect engine to learn on as they are very knock limited if you have access to the software you will most likely see the knock control retarding the timing at that point. this is why it would have done it and then gone away

Regards Ross