Large heavy utility diesel trucks like garbage trucks have huge engines, extreme start-stop patterns, lots of shifting. Those are loud by themselves. Also, they are low production volume and are only noise insulated in as far as regulation requires them.

https://www.washingtonpost.com/business/economy/americas-bes...

I know from the hybrid buses in Boston that they are a massive reduction in noise for the passengers. When you're at a stop, it is great to not have that engine idling. Electric will only be better in that regard.

The garbage trucks though seem to make a shit load of brake noise though. And noise from trash dumping on top of trash and being compacted.