5K250 SATA OEM Specification
Page 35 of 171
6.6
Acoustics
6.6.1
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
Typical (Bels)
Maximum (Bels)
Idle 2.4
2.7
Operating 2.6
2.9
Table 22. 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
6.6.2
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)
where
Lw = A-weighted sound power level
Pt = Value of desecrate tone penalty = dLt – 6.0(dBA)
dLt = Tone-to-noise ratio taken in accordance with ISO 7779 at each octave band.
