Hitachi hard disk 0J11285 500 GB 2.5 " 8 MB 0J11285 Ficha De Dados

Z5K500 OEM Specifications 

33 

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 hard disk 
drives is to be less than the typical value. Each hard disk drive is to be less than the maximum value. The 
hard disk drives are to meet this requirement in both board down orientations. 

A-weighted Sound Power 

Typical (Bels) 

Maximum (Bels) 

Idle 1.9 2.2 

Operating 2.1 

2.4 

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 hard disk drive supported by spacers so that the lower 
surface of the hard disk drive is located 25 ± 3 mm above from the chamber floor. No sound absorbing 
material shall be used. 

The acoustical characteristics of the hard 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 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 hard disk 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.