On Fri, 16 Oct 2020 16:53:48 -0700, John Foster wrote:

Much of the noise you hear from any propeller-driven aircraft comes from
the tips of the propeller breaking the sound barrier. That won't
change between an electric vs petrol engine.

True, provided that the prop diameter, number of prop blades and RPM are
the same.

The longer the propeller, the faster the tips move.

True only if the RPM stays the same.

The quietest propeller-driven aircraft I've heard is the Antares 20 - it
uses a large (2m diameter), slow turning two blade propeller. From 50m to
the side all you can hear as it accelerates past you on take-off is a
quiet fluttering/puttering noise.

At the other end of the scale, for shear prop-generated racket you can't
beat a CRESCO top-dressing aircraft - but you'll need to visit NZ during
the top-dressing season to hear that, unless your local jump club has a
CESCO PAC-750, which is probably just as loud.


--
Martin | martin at
Gregorie | gregorie dot org