Electric leaf blowers average 65db, 4 strokes are 70-80db, while 2 strokes average 90db. Where 10db is roughly double the "noise" I think this qualifies for "significantly"

It is not at all surprising that it’s much quieter as a result of putting ~40% of the energy into the stream of air.

You mean the sound per cfm isn't significant.

(source: I switched to Ego battery electric yard equipment from gas powered ones a few years ago).

The blowers I’d encourage you to look up the specs and make sure your quiet electric has the power your loud gas one had before finalizing your conclusion on sound output per air output. I doubt it has even half the power (unless your gas blower was a particularly small four-stroke).

I bought two plug-in blowers (both were bad jokes, being limited to 1.4kW of input power by the outlet) before buying a gas blower. I’ve since tried two battery blowers of friends and one of those was okay but still noticeably slower and less powerful than my gas blower (the other was similar to the plug-ins: suitable for dry leaves on smooth concrete).

I’m not at all opposed to electric tools (especially since small seasonal gas engines are a pain to keep running well); in fact I prefer them. But I haven’t found a blower that’s competitive in power and I’ve got maple seeds to move from 3” bluegrass in the wet New England fall and I’ve not found an electric that can do it.

However, the battery life isn't great, you get maybe 15 mins on a charge of those smaller 2ah batteries (but I have several along with a bigger 4ah mower battery). Perfectly fine for my yard, but not practical for a landscaper.