User Manual

A white paper issued by Siemens  September 2015

2.2 Silent Nozzle

The focus of all silent extinguishing concepts for inert gas extinguishing systems is the nozzle, the

place where most of the discharge energy is converted to acoustic noise.

Some concepts add silencers to conventional nozzles; Sinorix Silent Nozzle reduces the noise level

at the source without affecting the performance (gas flow rate and distribution) of the nozzle.

Figure 8: Principle of Sinorix Silent Nozzle

Sinorix Silent Nozzle operates on the principle of a two-stage gas flow expansion. The orifice at

the inlet of the nozzle determines the hydraulic resistance and hence the flow capacity of the

nozzle. The pipe network pressure p

PIPE is significantly reduced to the nozzle inside pressure

NOZZLE. This first expansion releases a significant amount of the energy but keeps the associated

expansion noise inside the nozzle. The second expansion from the nozzle inside

pressure pNOZZLE to the ambient pAMBIENT represents a much lower level of pressure drop.

Another benefit of the Silent Nozzle’s design is that the total noise generated by the numerous

small discharge jets is lower than that generated by a few large ones, and the emission spectrum

of small jets is shifted to higher frequencies.

Figure 9: Spectral behavior of Sinorix Silent Nozzle vs. standard nozzle

*) LZFmax per third-octave band

― Standard nozzle

― Sinorix Silent Nozzle

[dB]*

Maximum normalized to 0 dB

f[Hz]

Reduction

Shift