HI everyone
I have a 2018 RDX tech, it has 106,000 KM on it so this noise only comes on during cold starts once the engine is warmed up and goes away. I've checked out underneath the car and found nothing loose. I'm trying to avoid going to the shops, I am more of a DIY person. Any suggestions would help me a lot thanks in advance by the way I've attached the sound clip

 

It sounds like something that spins like a pulley or something...

 

Thanks for the input, I'll check that out tomorrow and update you guys on it.

 

Hey everyone
I​​​​ got an update on the noise, so it's coming from the manifold converter heat shield located behind the engine, put some clamps on it now the noise is gone. Heat shield bolts gets loose in time

 

Thanks for the update.
Have totally the same sound on my RDX and dealer could not fix it because could not reproduce the sound on warm engine.

 

Holy moly. I've been searching all over to see if anyone has the same problem (and solution) and your sound is exactly the same thing I'm hearing in my 2013 RDX. Right after a cold start, this buzzing sound kicks in and goes away after 10-20 seconds. I went as far as replacing my accessory belt and tensioner. I was going to go down the route of engine starter next. If it's just a vibrating heat shield I will be more than pleased.