Aircraft Engines Tones / Noises

Dear All,

Can someone distinguish between the aircrfat engine types from its noise?

Let me give you some noise related factors in a way of giving some differences between two types of engines installed on A320/A321.

These engines are V2500 and CFM56-5A/5B.

The V2500 has different noise tone than the CFM56-5A/B. Some of differences related factors are:

1- The V2500 has different number of stages (Compressor Stages / Turbine Stages) from CFM56-5A/B.

2- There are something called noise acoustic panels installed at the inlet of engines. These panels are used to absorb the noise coming out from the engine. Also, these panels are different in shapes, sizes, and material between the V2500 and the CFM-5A/B.

3- Every Turbo Fan Engine inlet air is divided into two parts:
A) Primary Air which goes into the engine compressor stages and turbine stages through the combustion chamber. This air that cause the engine to run. This air will be exhausted outboard. B) Secondary Air that is withdrawn by the fan at the engine inlet and discharged overboard through bypassing around the main engine components and not inside the engine. At the end also the secondary air will be discharged outboard the engine to the air.

Now on the CFM56-5A/5B the exhausted primary air will be discharged seperately to the outboard from the secondary discharged air. The primary air will be discharged through component called "Center Body". On the V2500, it is different as both the primary engine air and the secondary engine air will meet together when discharged in a component called CNA - Common Nozzle Assembly.

This design gives alot of advantages for the V2500 engines. One of the important advantages is REDUCING THE NOISE. Again mixing the discharged PRIMARY AIR with SECONDAR AIR will reduce the noise or at least smoothen it.

4- Every engine type build from different materials, specifications, inlet area, outlet area, valves such as VSV - Variable Stator Valve - , VBV - Variable Bleed Valve, VBSV - Variable Boost Start Valve, number of fan blades, area size of the fan blades,....etc other than the other type of engines.

Believe me, every engine and if I can use the word TONE has different tone from another engine type BUT all engines from the same type has the SAME TONE.

I believe that what I have briefed above are so far helpful information as I also believe we can talk alot about many other factors. But I can say the above are the main factors.

B.Regards
Ayman Shak'ah
Licensed Aircraft Maint. Engineer