User Manual

A white paper issued by Siemens  September 2015

With the capture and evaluation of the sensitivity profiles of hard disk drives in the frequency

spectrum, a maximum noise sensitivity of the hard disk drives tested has been found in the middle

audible frequency range. Each hard disk drive, however, has a typical sensitivity profile with char-

acteristic performance degradations at a specific resonance frequency and multiples thereof.

Siemens defined the different sensitivity levels of hard disk drives in the sound spectrum:

 Hard disk drives are not sensitive to noise in frequencies below 500 Hz

 Certain hard disk drives demonstrate a sensitivity to noise in frequencies from 500 Hz to

1.6 kHz

 The range from 1.6 kHz to 8 kHz is the most critical range in the spectrum

 Certain hard disk drives demonstrate a sensitivity to noise in frequencies from 8 kHz to

12.5 kHz

 Hard disk drives are not sensitive to noise in frequencies above 12.5 kHz

Figure 7: Empirically determined frequency-specific sensitivity profile of HDDs

*) LZFmax per third-octave band

1.3 Are the laboratory results transferable to

actual installations?

In order to observe the effects on HDDs exposed to full-scale extinguishing discharges,

Siemens performed more tests using the same performance measurement setup and HDDs during

actual extinguishing discharges.

A series of tests was conducted using the following inert gas extinguishing systems from

Siemens:

 Sinorix N

2 unregulated system with nitrogen at 300 bar cylinder pressure

 Sinorix CDT regulated system with nitrogen at 300 bar cylinder pressure, CDT valve

Conclusion

The noise of an inert gas extinguishing system may impair the performance of a hard disk drive

during the extinguishing process. However, neither data loss nor permanent damage to a HDD

was ever observed in a test.

Severe performance degradation

and faults

Performance degradation

Undisturbed operation