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6.7 Acoustics
6.7.1 Sound power level
The criteria of A-weighted sound power level are described below.
Measurements are to be taken in accordance with ISO 7779. The mean of the sample of 40 drives is to be
less than the typical value. Each drive is to be less than the maximum value. The drives are to meet this
requirement in both board down orientations.
A-weighted Sound Power
48 GB model
30 GB and 20 GB models
All other models
Figure 33. Weighted sound power
The background power levels of the acoustic test chamber for each octave band are to be recorded.
Sound power tests are to be conducted with the drive supported by spacers so that the lower surface of
the drive be located 25±3 mm above from the chamber floor. No sound absorbing material shall be used.
The acoustical characteristics of the disk drive are measured under the following conditions:
Mode definitions
!
Idle mode: Power 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 the actuator with a
dwell time at each cylinder. The seek rate for the drive can be calculated as shown below.
Ns = 0.4/(Tt + T1)
where:
Ns = average seek rate in seeks/s
Tt = published seek time from one random track to another without including rotational
latency
T1= equivalent time in seconds for the drive to rotate by half a revolution
Typical (Bels)
Idle
Operating
2.5
2.4
2.1
Travelstar 60GH & 40GN hard disk drive specifications
Maximum (Bels)
Idle
Operating
3.5
2.7
3.8
3.1
2.6
3.3
2.7
2.4
2.9
37
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