Like many other threads on here, I found my new DS-7608NI-K2-8P unbearably loud. It has a channel well technologies PSU (KSA-180S2) with a 12v 5A rail, a 52v 2.5A rail and a really noisy 40mm fan, and then a second not-quite-as-noisy 40mm fan on the case.
Everyone has a different sensitivity...