I have just purchased a new 2018 Mac Mini with a SSD drive.
Sometimes when reading or writing, it makes a quite screetchy noise. It's not loud, but however it's quite sharp which made me cautious.
I was under the impression that SSD's don't make any particular noises. I have a MacBook Pro Late-2017 with a SSD, and I never hear it make any noises when read/writing.
Please have a listen to the audio file below. Note that the microphone is close to the computer, so the fan and screetch noise is relatively loud in the clip. In reality, it's noticeable but quite muted. Most of the screetch noise is heard in the beginning.
Perhaps it's not even the SSD making these noises?