We’ve made considerable effort to make sure we took accurate measurements of the noise and heat production levels of the harddisks tested. For the noise production, or rather sound pressure level, measurements we’ve used a professional sound pressure level meter costing several thousands of dollars and calibrated according to IEC-60651, Class-1. The actual measurements are in dB with an A-weighted curve to fit the sensitivity of the human ear, the maximum error is +/- 0.7dB. All of the given values are therefore in dB(A). All of the harddisks tested were mounted in a soundproof and fully insulated enclosure so as to make sure we measured the sound level generated by the harddisk and not the ambient noise. The microphone in all of these tests was at a distance of 25-cm or 10-inch from the top surface of the harddisk.

Because the measurements are in decibel (dB) we do need to take into account that decibels are measured on a logarithmic scale. So it is important to note that a sound pressure level of 30-dB isn’t 10-times higher than 20-dB but 100-times. For example, if comparing a sound level of 60-dB, a normal conversation, to 90-dB, an average lawn-mower, there’s a 1000-times difference in sound pressure level. So decibels are a lot harder to quantify because a doubling in sound pressure level isn’t simply a doubling of the dB value.

Sound Pressure Levels:

0-dB	-	threshold of hearing, total silence
15-dB	-	whispering, leaves rustling
30-dB	-	very soft music, dishwasher
60-dB	-	normal conversation, vacuum cleaner
90-dB	-	lawn-mower, motorcycle
120-dB	-	threshold of pain, jet-engine
150-dB	-	hearing damage, heavy fireworks

The temperature measurements are done with a professional, laboratory grade, digital thermometer calibrated in degrees Celsius with a maximum error of +/- 0.1 degree. All the measurements are done in the open air with a constant room temperature of 21 C/ 70 F. De actual measurement is to the upper side of the drive with the probe attached to the metal top with a clamp at a set pressure. The drive was used for an hour prior to the measurement and the average temperature over a period of 15-minutes was used as the result. The result reflects how many degrees the harddisk is warmer than room temperature, as this will help you to determine what the harddisk’s temperature will be when mounted in a system with a certain temperature. If you however are interested in the actual disk temperature under the conditions we tested just add 21 degrees Celsius.

Test system configuration:
Asus P4T-E motherboard, i850 chipset
2 x 256MB Samsung PC-800 RDRAM
ATI Radeon 8500 64MB
Toshiba SD-M1612 DVD/CDROM
Windows XP Pro with latest updates