Propeller noise is largely a function of rotation speed, blade size, and radius.

Electrical motors have high torque and are basically silent. Torque limitations constrain the blade size on a helicopter. The whop whop comes from the relatively long blades. And because of the large diameter that happens at a relatively low RPM. So, the frequency of the noise is low as well. Hence the whop whop sound.

Higher torque electrical motors enable higher RPM with smaller diameter and more blades. So, you get a higher frequency noise. Higher frequencies carry less far than lower frequencies. So, a lot of drones are measurably more quiet than helicopters when they fly overhead because they have lots of smaller propellers spinning faster. There's plenty of footage of electrical planes and drones taking off and landing at airports, air shows, etc. Some youtubers also use decibel meters. This has long stopped being a matter opinion / debate, you can just go out and measure it.

The short version of it is that these things are quieter, as the physics suggests.