My MacBook Air 2013 is routinely the loudest machine in the room when it's compiling or similar.

Does it have fans? If not, what kind of noise is this ?

MBAs have fans, the 12" MacBook doesn't.

Possibly inductors vibrating.

"Coil whine".

No, the sound comes mostly from the fans, which when at their maximum start to get loud.

Oh...it’s not just me then.. Every couple of months I check my 2015 MacBook Pro system info because I’m utterly convinced that it has an hard drive because of the SSD noise. It’s quite frustrating actually..

Imagine being a kid in the 80s or 90s at school and hearing the distinctive 20k tone of a CRT Television humming and wondering if you were going to be watching TV in one of your classes that day. It was like a dog whistle for kids.

If you're in the US or anywhere else with NTSC, the horizontal scan rate (and thus the whine of the flyback transformer) is 15.75 kHz :)

525 lines / 2 for interlacing * 60 fields per second = 15750

times 1000/1001 ever since color was introduced, so about 15734 Hz

For me that was a thing until the late 2000's.

They were still using CRT TVs in 2012 when I finished high school. I wouldn't be surprised if there were still plenty of schools with CRT TVs and VCRs for educational material.

I still have a 19" CRT[0] as 2nd monitor at work because... why not?? It still works most of the time and supports a decent resolution (1400x1050 - 1600x1200 flickers). And it's a nice nostalgic conversation piece :)

[0] https://www.cnet.com/products/compaq-s910-crt-monitor-19-ser...

Back around 2001 I took my desktop build (Celerin 300A oveeclocked to 450MHz), installed a giant passive heat sink on the CPU and PSU, put in an 8MB IDE flash drive, and network booted off a server in my laundry room. I thought I was finally noiseless. But the end result was worse. I had coil whine out of my power supply any time CPU usage ramped up. If I was in the same room, I could tell whenever my email pinged the server or if a cron job ran. It was both instructional (why is my cpu ramping and I’m not even logged in?) and really annoying.

I had one of those, I think it may have overclocked to 550MHz, I can't remember for sure. The cooling fan was audible outside of my house!

I’m routinely annoyed by what I am reasonably sure is the sound of my MacBook Pro’s heat pipes and other warm components expanding and contracting, making creaking noises shortly after starting it up on a winter day. Then there’s the gentle gaseous hissing I would swear is the heat pipes condensing and evaporating (based on workload and laptop temperature concurrent with the noise) if I could think of a practical reason for them to be audible.

No, it's not just you. I can hear the SSDs in two of my laptops.

So does my Kingston SSD. And the switching of my switching power supply sometimes (rarely) is the loudest thing in my desktop pc.