The noise level of TeSys D range of contactor is less than or equal to 35dB.
This is one of the control parameters during the testing of the TeSys D contactor.
Method for reducing the Noise:
The best method to reduce the noise during Opening/Closing of contactors is to mount the contactors on silent blocks easily available in the market (rubber shock absorbers).
Also, you can put the contactor in an acoustic enclosure so that sound will minimize outside the enclosure.