Engine sound oscillation? / Inconsistent engine noise.

[subiesnack]

TubHey all, first time posting to a forum, so forgive me if this being posted in the wrong spot etc.

Ive noticed a strange '' oscillation '' in my engines noise as I'm driving. Finding it hard to describe.. So bare with me �� It only really happens between 2900ish to 3500ish rpm. The actual engine sounds normal, but its as if it gets loud then quiet, loud then quiet etc. It starts slow ish, but gets faster until about 3500 rpm when it fades and the engine sounds consistent again. I can feel a slight vibration in my gas pedal which is in sync with the oscillation. Doesn't seem to matter which gear I'm in. I should also note that it seems louder if I'm going up a hill or the engine is under more load.

The car is a 2002 Subaru legacy 2.5 N/A

Standard transmission

140k miles.

 

Ive just had the head gaskets replaced, fairly new spark plugs, pcv valve, fuel filter. (I noticed the noise when I got my car back from the head gasket repair, but it may have been there before and I didn't notice)

I have no clue what could be causing this, or maybe it's just the way these boxer engines sound?? This is my first subie. It doesn't sound "broken" haha. It feels solid and runs well.

Edited October 22, 2019 by subiesnack