Noise reduction

[David Findlay]

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

[Robert Schieck]

David Findlay wrote:

> I'm interested to know what people have done in their aircraft to reduce
> the interior noise level?

Build a glider <g>...

sorry , couldn't resist

Rob

[Kyle Boatright]

"David Findlay" > wrote in message
...
> 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 are plenty of ways to reduce noise in a homebuilt, but unless you're
willing to go to extreme lengths, you'll have a hard time getting a
homebuilt down to the levels you mention. The 4 stroke rotax engines are
relatively quiet, so a design using one of those would be a good starting
point. Beyond that, you'd need to add insulation and go to thicker glass to
make a noticable difference.

Noise cancelling headsets are the most cost and weight effective method to
reduce percieved noise.

KB

[Jim Logajan]

"Kyle Boatright" > wrote:
> "David Findlay" > wrote:
>> I'm interested to know what people have done in their
>> aircraft to reduce the interior noise level?
>
> There are plenty of ways to reduce noise in a homebuilt, but unless
> you're willing to go to extreme lengths, you'll have a hard time
> getting a homebuilt down to the levels you mention.

I'm curious about the noise aspect also and was wondering whether pushers
are any quieter or smoother rides than pullers?

[Smitty]

In article >,
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 was a great article in the April 2005 issue of Sport Aviation (EAA
publication) entitled "Taming the Noise." It's a great article,
explaining the acoustic principles at work, and offering insights into
how to deal with many different types of noise in different ways.
Insulation is only one tool in the battle against noise. Taming the
source (i.e. prop and engine balancing,) preventing the transmission
(isolation mounts,) and absorbing the reflected noises (carpeting and
other upholstery) are some of the other measures discussed. The author
and his associates were able to reduce the noise in their "test
airplane" by almost 8 dB fairly readily, at a modest penalty of 23 lbs.
It's also important to have a well-sealed cockpit. Stop the air leaks
and you stop all of the direct noise leaks. The rest of the noise is
"just" transmitted noise that comes in the form of vibration.

[Corky Scott]

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

[Michael Pilla]

"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

[David Findlay]

> I'm curious about the noise aspect also and was wondering whether pushers
> are any quieter or smoother rides than pullers?

I'd be interested to know that too, because the main candidate aircraft for
me is a pusher prop one(The Aircar - it's a 4 seater wooden seaplane).
Thanks,

David

[George A. Graham]

On Fri, 15 Jul 2005, David Findlay wrote:

> I'm interested to know what people have done in their aircraft to reduce
> the interior noise level?

My airplane is fairly quiet inside. I borrowed a Db meter, and it
registered 82 in cruise IIRC, about the same as my van with the window
open. Mine is a pusher which may help, and it is built of foam and
fiberglass, not metal, which may also help.

We do wear headsets most of the time, but can talk without them if our
ears get tired of being clamped. I have no speaker installed, so can't
hear the radio without them.

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[George A. Graham]

On Sun, 17 Jul 2005, George A. Graham wrote:

> My airplane is fairly quiet inside. I borrowed a Db meter, and it
> registered 82 in cruise IIRC, about the same as my van with the window

Egads, my memory is shot! I just checked my website.
The Db meter was 93 at 150 mph, and 97 at 185 mph.

Sorry about the misinformation. Still it seems quiet.

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[Roger]

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
>