Noise, Vibration and Harshness (NVH) is the study of rattles, vibrations and other noises with a view to improving the automobile to make it quieter, smoother and better riding. Nissan implemented NVH improvements by the 1973 introduction of the B210, if not sooner.
For many details of NVH in general, see wikipedia:Noise, Vibration, and Harshness.