The noise levels of the drives were measured in a soundproof box at a distance of 10 cm; both when the drives were idle as well as during a random workload. Note that the numbers should be interpreted as follows: everything under the 30 dB(A) threshold is essentially inaudible at a normal distance. Everything under 40 dB(A) is as quiet as a whisper at a normal distance. Drives that exceed the 40 dB(A) threshold are clearly audible.
The Western Digital Red 8 TB and the Seagate IronWolf 10 TB, the two drives in this test with helium, are the quietest, while the other Red-drives are mostly silent and the Seagates but primarily the HGSTs produce a lot more noise.