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Old 11th Jun 2003, 23:42
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Intruder
 
Join Date: May 2000
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The primary/loudest noise from the front engine will almost always be from the fan. Not only the fan speed, but the number of blades will determine the basic noise frequency. Since noise is propagated in air, the movement of more air (i.e., higher thrust settings) will also directly affect the volume/level of the noise.

The character of the perceived noise will be affected by local airflow through the inlets, the frequency and level of noise that emits from the compressor section, exhaust noise that can be heard from in front of the engine, vibrations in the nacelle and airframe caused by the main engine noise, and interactions between all those noise sources, vibrations, and structures.
Noise that we perceive as whines, growls, hoots, and shrieks are the products of those interactions.

The 2-spool vs 3-spool configuration undoubtedly makes SOME difference in perceived noise, but it would be in the secondary interactions more than in the primary fan noise.
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