Delivery drones are larger and therefore quieter (larger propellor = more pleasant tone and lower RPM) and fly higher than the consumer drones you’re probably familiar with.
Sounds is a funny thing. My physics professor once had us calculate the energy in the sound of an entire stadium and it wasn't enough to heat a cup of coffee. Sound just doesn't have that much energy. For a few hundred watts you can make an entire neighborhood miserable as any car audio enthusiast can demonstrate.
I routinely have Apache helicopters fly over my house and I prefer them to most of the tiny drones. The helicopters typically have lower frequencies and fly way higher. They also don't have that insect flying by your head buzz that makes my ears hurt.
"As you can hear for yourself, this Apache helicopter is nearly unnoticeable next to this handheld drone."