Why does the Apache create much more rotor noise than the A-129? The AH-64 Apache attack helicopter was upgraded several times after its first flight in 1974. The Apache Longbow was a major upgrade which entered service in 2003. On the other hand, Agusta A-129's first flight was in 1983.

I have two questions:


Why does AH-64D have much high rotor noise? Why wasn't there any effort to suppress the noise in the upgraded versions?
Why does A-129 have lower rotor noise (i.e. the chop chop sound is almost absent) even though its tail rotor isn't covered?
Because they are very different helicopters, as egid already pointed out.


The Apache is twice as heavy as the Mangusta (5165 kg vs 2530 kg empty)
The rotor diameter is also bigger accordingly (14.6 m vs 11.9 m)


A Chinook transport will make more noise than an Apache. An Apache will make more noise than a Mangusta. Different helicopters and different weights that have to be kept airborne.