Acoustics; Sound Power Level; Discrete Tone Penalty; Figure 12. Operating Mode - IBM DJSA-210 - Travelstar 10 GB Hard Drive Specifications

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
DJSA-232
Idle
Operating
DJSA-230
Idle
Operating
DJSA-220/210/205
Idle
Operating

Figure 31. 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 actuator with a
dwell time at each cylinder. 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

6.7.2 Discrete tone penalty

Discrete tone penalties are added to the A-weighted sound power (Lw) with the following formula only
when determining compliance.
Lwt(spec) = Lw = 0.1Pt + 0.3 < 4.0 (Bels)
Lw = A-weighted sound power level
Typical (Bels)
Travelstar 32GH/30GT/20GN hard disk drive specifications
2.5
3.5
2.8
3.5
2.8
3.3
37
Maximum (Bels)
2.7
3.8
3.4
3.8
3.4
3.6