Shining Arcanine wrote:
The amount of surface area increases by a factor of two when the platters are doubled. The motor primarily generates vibrations (due to the FDB) so when a drive is suspended, the motor noise is insignificant compared to the noise generated by the motion of the platters.
The number of platters is directly proportional to the amount of noise generated by hard drives with fluid dynamic bearings in any given hard drive family
HDD noise (even with FDB motor) is more than just air turbulence. It's bearing whine/grind (no longer present when there's no metal/ceramic ball bearings), motor coil whine (changes of current in the coil causes it's core to change shape repeatedly and produce high frequency audible noise), whine produced by electorics on the PCB, etc.
What you're saying is that wind noise is the only form of noise FDB drives produce, yet when performing subjective evaluation, we might find that some drives (even with FDBs) produce high-pitch noises and pure tones. These cannot be produced just by air turbulence which is quite broadband.
Shining Arcanine wrote:
If SPCR really disregards the platter count as a factor in noise generation, would SPCR be so kind to review mutiple drives with different platter counts from a single family (e.g. the Western Digital Caviar family) and determine the acoustical, vibration and energy properties of each one?
Do you consider WD Caviar a single family of drives? No way. WDs are the least predictable drives when it comes on drive "families".
1) you take two drives manufactured the same month, like WD5000 and WD3200/2500 or WD3200/2500 and WD800 they're not the same family! They don't even look the same.
2) you take two drives of same name (like WD1200BB) but manufactured different months. One might be 1 platter, one might be 2 platter, and the oldest probably 3 platters. Also the base casting might change during the several year of manufacturing and I can guarantee there's nothing common with todays WD400 and the WD400 when it was introduced very long time ago.
WD is the least predictable when it comes to telling the number of platters used without actually opening the top cover and counting them visually. Maybe using a scale could help... but the differences in weight isn't that big and the weight of an "empty" HDD without platters vary between different families (and "WD800" for example isn't a "family" but several families).
Seagates aren't predictable either. Their "families" also consists of several data densities and even capacity points have different samples ranging from clipped head to short-stroked.
The product family concept has become more vague lately with even Hitachi combining different densities in their "family" T7K500. T7K500 250GB for example is closet to T7K250 250GB than T7K500 320GB.
Shining Arcanine wrote:
If the hypothesis that the number of platters is irrevelent is correct, there would be no acoustical difference between the drives.
There is a relation. But the relation isn't necessarily as simple as direct propotionality (as you suggested). If we deny your theory of direct propotionality, you say the consequence of denying it would mean there's no reliation at all. That's BS.
Shining Arcanine wrote:
If the hypothesis that the number of platters is directly proportional to the amount of noise generated by hard drives is correct, then there would be measureable differences between various platter counts, with a three decibel difference between two and four platter drives.
Yes...
IF.