6.10 Acoustics
The following shows the acoustic levels.
6.10.1 Sound Power Levels
The upper limit criteria of the A-weighted sound power levels are given in Bel relative to one pico watt and
are shown in the following table. The measurment method is in accodance with ISO7779.
Background power levels of the acoustic test chamber for each octave band are to be recorded.
Sound power levels are measured with the drive supported by spacers so that the lower surface of the drive is
located 25 ± 3mm height from the chamber desk. No sound absorbing material shall be used.
The acoustical characteristics of the drive subsystem are measured under the following conditions.
Idle mode:
Powered on, disks spinning, track following, unit ready to receive and respond to control line
commands.
Operating mode:
Continuous random cylinder selection and seek operation of actuator with a delay for a time
period achieving the required seek rate Ns according to the following formula:
Ns = 0.4 / (Tt + Tl)
where:
Ns = average seek rate in seeks/sec.
Tt = published random seek time.
Tl = time for the drive to rotate by half a revolution.
Figure 51. A-weighted Sound Power Levels
Mode A-weighted Sound Power Level [Bel]
Idle 3.8 (Typical) 4.2 (Max)
Operating 4.5 (Typical) 4.8 (Max)
56 OEM Spec. of DDRS-3xxxx
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