The H130 has Pedal Position sensors (or transducers) and alters it's Nr because of the inputs recieved therefrom. The offical reason is some nonsense about being quieter (and it is very quiet), but the real reason is likely to be to produce more TR thrust in the hover
I still believe this is very improbable.
Other ABH types also vary Nr automatically to reduce the noise signature, but they do it as a function of altitude. One type I am familiar with varies from 342rpm at SL to 350rpm at 5000 ft and above.
Edit: a bit of research finds this ICAO research paper on Helicopter Noise:
http://www.icao.int/environmental-pr...April_2015.pdf
Variable rotor speed law depending on air density and airspeed
(for the H130)