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 Gold 10TB is the quietest in idle, but fortunately all drives are noiseless when they are not under load. Unfortunately the Gold is relatively loud under load, with clearly audible noise levels of over 40 dB(A). The BarraCuda Pro is relatively quiet both in idle as well as under load.