As mentioned a modern harddisk still is a mechanical device, and as with most mechanical devices it is hard to completely cancel out all noise. One part that contributes to the noise significantly is the spindle, which drives the platters. The spindle is usually direct-driven and has an rpm of 5400 or 7200-rpm, which translates itself into a high-pitched whine. Harddisks that use high-quality bearings or even fluid-bearings are less noisy in this respect than others that use conventional bearings. Then there are the harddisk platters; due to the high speed at which they revolve they generate both noise and heat. And naturally the more platters, higher capacity harddisks, the more heat and noise are generated. Due to space constraints modern harddisks don’t use more than four platters which does limit the heat and noise production to a certain level.
Fortunately a manufacturer has a number of options at hand to reduce the noise level of the spindle and platters, such as using high-quality bearings or decoupling the spindle and spindle-motor from the harddisk casing by using a sound and vibration dampening gasket. Of course another way to reduce the noise and heat production would be to use less platters of a higher density, as this will not influence the storage capacity of the disk.
Fig 1. The interior of a typical harddisk whilst operating. This movie requires the Windows Media player to be installed and requires a broadband connection for streaming playback.
But there’s other moving parts that also contribute to a harddisk’s noise production; the read/write heads are notorious for causing the ‘rattling sound’ many harddisks make when accessing your data. And again the manufacturer has a number of options to reduce this noise which usually mean that the heads are operated less abruptly when sweeping across the platters. For example by smoothing out read/write operations by slowing the heads down when they need to reverse direction or by intelligently combining read and write operations and thus reducing head movement. Unfortunately many of these noise reducing measures do affect the harddisk’ performance and some can even be set arbitrarily through software to optimize for a specific application.
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