Low hum after starting the engine (BRZ MY 2017)
 

So I noticed this somewhat odd noise the past week.

Basically I turn on the engine and let it idle. The first 10 seconds from starting sound fine or like a normal car idling, but after that time there's a low hum that starts to happen behind the driver seat (originally I thought it was more on the passenger side but tonight makes me think it's behind the driver).

The hum lasts about 20 to 30 seconds and then stops. It never changes pitch. I think I've heard it while driving a couple of times but the pitch never changes then either.

I had a weird thought just now that it could be a weird bluetooth and sound system issue since it's sort of like feedback on a speaker, so I turned off bluetooth on my phone and kept the sound system "muted" (I believe that means entirely off?). However, the hum happened anyways.

My car is completely stock.

Here's an example: https://app.box.com/s/8nvnqj3g0kxou9cnm4lu7ykrtnsjs20b

The "hum" starts about 6 or 7 seconds in. The pitch changes but that's from me moving my phone closer to where I assume the sound is coming from, rather than the sound itself changing. It's the same every time I hear it.

I looked on the forums but the only somewhat similar noise I could find discussed was for the fuel evaporation test or similar, and from what I saw that should happen when the car has been off 5 hours. The fact that I can repeat this issue within 5 mins when restarting the car 3 or so times looks to refute that as a possibility.

Anyone else come across this? May need to bring it to the dealer...

Can't hear anything weird on the clip. From your description I am guessing that it is just exhaust resonance at certain RPM during the warm up period. As the cats get warmer the sound changes a bit and you may be just noticing that transition. Next time it does it just give it a touch of gas and see if it changes.

I think I hear what you are talking about, kind of a low-frequency hum, and I think tcoat is right. It sounds like the exhaust.

Time to install a loud exhaust to kill crickets, hums and buzzing! :lol:

Does the 2017 MT still have the cursed crickets?

Why not, would seem sensible. Or take it to the dealers in English.

Sometimes.

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Speaking of English, do you speak it?

In English? I was planning on taking it to the ones en français

I personally haven't heard them in the 9 days I've had my car.

Yes. Well, mine is AT so it has the older engine. They started about 2 weeks ago. I bought it in Oct of 2016.

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I hear it clearly (I have surround speakers on my computer)...it sounds like a constant fog horn way off in the distance. Never hear that in my '13 but I can tell you these cars have lots and lots of odd noises that I have never heard in 30 years of driving.

Aw man, I was hoping to be reunited with my little cricket buddies when I bought my next 86/BRZ! They kept me from feeling lonely on road trips...

You heard them while moving? I thought they just showed up when idling. I could make them come and go even at idle just by adding a few revs. I felt like an orchestra conductor.