whats up mazda 3 owners

I've been experiencing this weird whistle noise coming from my transmission/engine bay. It makes the while on cold starts. When I drive between 20 - 60 miles mph it makes that noise and periodically stops and the noise comes back again. I can hear it outside of the car and while inside the car.

Model: 2017 Mazdel 3 hatchback GT japan model 48k miles, routine oil changes every 5000-7500 miles, 1 set of new tires, tire balance every oil change, 1 set of new front brake pads + rotors.

Here's the sound in this link:

https://drive.google.com/file/d/1CWB...ew?usp=sharing

It started a week ago and I did some searching on reddit and other mazda3 forums and common theme were an axle problem that need lube or faulty transmission during assembly (TBS: MC-10155437-0001.pdf)

I went to the dealership earlier and they scheduled me for an appointment to further diagnosis if it is in fact the transmission being faulty. If it is the transmission they will waive $180 fee and replace the transmission with a new one.

However, it is isn't they will charge me $180 + fees to fix that whistling noise.

Does anyone know how I can find the transmission serial number without taking apart parts from the engine bay or is it visible to the naked eye if I lift the car?

Has anyone ever experience this same noise with similar mazda 3 models (sport, 2.5, or GT), CX-5, or mazda6?