To be more pedantic, it's probably safe to assume this is not even 0dB. Most people would probably consider a computer under 25dB-30dB as "silent" since most rooms background noise are around there.

Linus did a silent PC build which even in a sound proofed case and at idle was about 14dB and broke 20dB under load: https://www.youtube.com/watch?v=RXZrWqCT7R0

Even the high end microphone used to record the sound level in this video produced it's own 7dB of noise.