Acoustics; Sound Power Levels; Table 27: Weighted Sound Power - Hitachi HTS421212H9AT00 - Travelstar 120 GB Hard Drive Specifications

The shocks are applied for each direction of the drive for three mutually perpendicular axes, one axis at a time.
Input levels are measured on a base plate where the drive is attached with four screws

6.6 Acoustics

6.6.1 Sound power levels

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.

Table 27: Weighted sound power

120GB, 100GB, 80GB
models
60GB, 40GB models
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 com-
mands.
• 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 is calculated with the following formula:
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
Idle
Operating
Travelstar 4K120 Hard Disk Drive Specification
A-weighted sound power
Maximum (Bels)
2.3
2.7
2.0
2.4
36
2.6
2.9
2.3
2.6