Buzzing/Humming sound at high idle
 

Hello all, this is my first post so I hope that this is in the right section. I have a 2015 BRZ Limited 6mt which has around 550 miles on the odometer, around 120 miles or so it started making a weird metallic buzzing or humming sound on a cold idle in neutral from 1200 RPM to about 2500 RPM or so. After the car was warm enough to idle around 500 RPM I could replicate the noise by blipping the throttle in that RPM range but as soon as it goes below the 1200 RPM mark the sound abruptly cuts out. The buzzing sounds like it is coming from underneath the car or near the rear of the vehicle almost maybe from the exhaust but I cannot pinpoint the location exactly. I took it to the dealership and they insist that it is a normal sound that it is the high pressure fuel pump kicking in but this doesn’t make sense as the sound seems to be coming from underneath of the vehicle. I know that it is not coming from the speakers or anything like that. This noise is making me concerned, do you guys have any input on what it may be? It is very noticeable and the BRZ I test drove definitely did not make this noise. It is not the chirping that we all know about because my car has that too and I have grown to ignore that but this is very different.

Is it like a rattling type sound? I got metallic rattling on my car within 1000 miles of ownership. I looked under the car and discovered one of the metal band clamp things on the exhaust heat shield had come loose. Just had to get under the car with a wrench and tighten up and it's all fine now. So that's one possibility.

^^ This.
There have been many people mention the buzz and almost every single one of them was a loose heat shield. Really easy fix from what I have read.

Okay awesome I was hoping it would be an easy fix thank you guys

Please let us know what you find out.
It may help somebody else down the line.

I will definitely post up if that was the cause, I am currently out of town but as soon as I return I will let you guys know.