Noise reduction

On Fri, 15 Jul 2005 02:20:37 GMT, David Findlay
wrote:

I'm in the early stages of the homebuilding disease :-P and still don't
know exactly what I want to build, just that I want to build something.
I'm interested to know what people have done in their aircraft to reduce
the interior noise level? Can such noise insulation be added to plan or
kit built aircraft without too much difficulty? Is it possible to reach
car or commercial airline jet noise levels in a homebuilt? Thanks,

David

There's a LOT you can do to reduce noise in the cockpit. Most of it
has to do with proper use of insulating materials but there are other
things like taking extreme care in sealing things like doors and
windows. Using double panes in the side windows will help. Using a
thicker plexiglass for the windshield makes a difference and adds
value in bird strike protection. Putting an effective muffler on the
engine will help too. All this costs money and adds weight.

I recently added two mufflers to my V-6 engine mounted on the test
stand because I thought the neighbors would object to the very loud
barking of the headers while I ran it for extended periods. The
mufflers cut the exhaust noise to a muted burble, but the prop is
sounding loud now even though I haven't had it beyond 1,500 rpm yet.
I won't be able to use the mufflers in the airplane because they are
too big to fit. They are also too heavy. But there are other
mufflers that I could use that are much more slender and lighter when
the time comes to install the engine in the fuselage for good.

Corky

"Corky Scott" wrote in message
...
On Fri, 15 Jul 2005 02:20:37 GMT, David Findlay
wrote:

I'm in the early stages of the homebuilding disease :-P and still don't
know exactly what I want to build, just that I want to build something.
I'm interested to know what people have done in their aircraft to reduce
the interior noise level? Can such noise insulation be added to plan or
kit built aircraft without too much difficulty? Is it possible to reach
car or commercial airline jet noise levels in a homebuilt? Thanks,

David

There's a LOT you can do to reduce noise in the cockpit. Most of it
has to do with proper use of insulating materials but there are other
things like taking extreme care in sealing things like doors and
windows. Using double panes in the side windows will help. Using a
thicker plexiglass for the windshield makes a difference and adds
value in bird strike protection. Putting an effective muffler on the
engine will help too. All this costs money and adds weight.

SNIP

Corky

======================
While building my RV-4, experienced builder/flyers strongly recommended that
I add very lightweight angle aluminum stiffeners along the long expanses of
unsupported aluminum sheet. These very thin strips of right-angle aluminum
stiffeners are intended to reduce the oil-canning and reduces noise from the
slipstream drumming along the sheet metal expanses.

Michael Pilla

On Fri, 15 Jul 2005 14:43:17 GMT, "Michael Pilla"
wrote:

"Corky Scott" wrote in message
.. .
On Fri, 15 Jul 2005 02:20:37 GMT, David Findlay
wrote:

I'm in the early stages of the homebuilding disease :-P and still don't
know exactly what I want to build, just that I want to build something.
I'm interested to know what people have done in their aircraft to reduce
the interior noise level? Can such noise insulation be added to plan or
kit built aircraft without too much difficulty? Is it possible to reach
car or commercial airline jet noise levels in a homebuilt? Thanks,

David

There's a LOT you can do to reduce noise in the cockpit. Most of it
has to do with proper use of insulating materials but there are other
things like taking extreme care in sealing things like doors and
windows. Using double panes in the side windows will help. Using a
thicker plexiglass for the windshield makes a difference and adds
value in bird strike protection. Putting an effective muffler on the
engine will help too. All this costs money and adds weight.

It's not a home built, but I have a 1/2" windshield, 1/4" side
windows, and lots of insulation in the Deb. It has a 260 HP IO-470N
which is almost always running 2400 except at take off where it's 2700
RPM.

The biggest change came from going to a 3-blade prop.
I was doing turns on a point and the guys on the ground said it
sounded much like a turboprop with very little noise.

It is still loud inside, but not nearly as bad as it was with the
2-blade prop.

BTW, with the sound proofing along with the thick windows flying in
torrential rain barely produces a noticeable sound. Doing the same in
the Old Cherokee 180 was almost deafening.

I've never ridden in a small prop plane where I didn't feel more
comfortable while wearing a head set. I actually find the noise very
distracting. Of course there are many small planes in which I haven't
ridden so there may be some out there that are quiet inside, but I'd
be surprised.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


SNIP

Corky

======================
While building my RV-4, experienced builder/flyers strongly recommended that
I add very lightweight angle aluminum stiffeners along the long expanses of
unsupported aluminum sheet. These very thin strips of right-angle aluminum
stiffeners are intended to reduce the oil-canning and reduces noise from the
slipstream drumming along the sheet metal expanses.

Michael Pilla