I use laptops, Apple workstations for the last 15 years since the days of PowerPC / PowerBook G4. I encountered the coil whine for the first time.
I upgraded to a Mac mini on i7 from a 2018 MacBook Pro. Because of Covid, I work mostly stationary. I needed more memory and performance. Generation and processor in both i7 computers. Obviously, I was lucky and my MBP did not have this annoying sound. May be that background ambient or coolers hid it.
On a Mac mini, I can clearly hear an annoying sound when it is running, including when no applications are running. It is clear that the background on the new computer is Spotlight indexing, FileVault encryption. After waiting a day. After installing all updates, upgrading to Big Sur, resetting NVRAM, SMC - the problem remains. The sound was extremely annoying and did not make it comfortable to use the computer.
I started to investigate that it could be the whistle of the coil and that modern SSD drives are not at all silent. As an engineer, I decided to test three components by loading each one separately. Which one is causing this noise to increase. SSD, Memory, CPU.
For benchmark tests, I used
SSD: Blackmagic Disk Speed Test
Memory: MemTest86
CPU: Geekbench 5, Intel Power Gadget
After completing SSD, Memory tests. I found no noise amplification. It was same under load/idle.
The CPU load caused this noise to increase in intensity. Further investigation of the problem led me to you, to other sources with Dell computers. Where is it talking about the feature of Intel's Coffee Lake generation (8 Gen) with Turbo Boost, that the increase in voltage causes this noise. Disabling Turbo Boost removed this sound, but reduced the performance of the computer in synthetic tests. I did not notice this in my work, but the tasks I perform do not completely utilize the processor.
On an Intel NUC with i5 Kaby Lake (7 Gen) I am using instead of Boot Camp. I also began to hear this noise. Although, earlier, I did not notice him. Disabling Turbo Boost or lowering the processor voltage eliminated it.
I had not previously heard this sound using this device. I thought about the peripherals of these devices. She was all new. Disconnecting and sequentially connecting / replacing the monitor, keyboard, WiFi, Bluetooth. Before to reached the power supply. Which is very logical, because the whistling of the coil causes an increase in voltage.
Both computers are connected to the network through an APC power filter by Schneider Electric, in my opinion the leader of electrical engineering. So, turning on each device directly, bypassing the filter, reduced this noise to a level that it ceased to be perceived. This does not eliminate it entirely. You can still hear at voltage peaks (see Intel Power Gadget) it if you bring the device close to you, listen. But sound is really more quieter.
Therefore, there is a dependence of the intensity of this noise on the power source, except for Turbo Boost. Try to run the test in different places, with different power supplies or vice versa, do not connect it to the mains.
Measurements of the voltage and its frequency with a multimeter did not reveal any differences in the network directly and through the filter. Voltage 228.7 and frequency 50 Hz - same readings. Unfortunately, I don't have an oscilloscope at my disposal to check the sine wave as well. The APC filter itself does not make any noise.
