Acoustics; Sound Power Levels; Sound Power Acceptance Criteria; A-Weighted Sound Power Levels - IBM DCAS-32160 - Ultrastar 2.1 GB Hard Drive Specifications

6.9 Acoustics

The following shows the acoustic levels.

6.9.1 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.
Figure 46. A-weighted Sound Power Levels
Mode
Idle
Operating
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.

6.9.2 Sound Power Acceptance Criteria

Statistical upper limit (L
(L ) = (L ) + k × (s
W stat W m
where:
(L ) is the mean value of the A-weighted sound power level for samples of N drives.
W m
(s ) is the total standard deviation for A-weighted sound power level.
t W
(s ) = SQRT( (s
t W
(s ) is the standard deviation for sound power level.
R W
Assume (s )
R W
(s ) is the standard deviation of the samples for A-weighted sound power level.
P W
k is a coefficient determined by number of samples (N) as shown below.
52
O E M Spec. of DCAS-34330/32160
) is calculated with the following formula.
W stat
)
t W
) ² + (s ) ² )
R W P W
= 0.075 B.
A-weighted Sound Power Level [ Bel]
4.5
4.8