Sound- absorption or reflection

[David Brady]

Ernie

Any insulation that's smooth is going to reflect the sound. In order
to absorb the sound you need a material with a 3 dimensional contour,
like an egg carton. You need the sort of material used in an anechoic
chamber.

http://en.wikipedia.org/wiki/Anechoic_chamber

The basic idea is that the cones cause reflections that destructively
interfere with the incoming sound waves; i.e., the reflections cancel
out the noise. The dimension of the cone is on the order of the
wavelength of the noise that you're trying to cancel.

The LXi uses a material very similar to what's shown in the above
wikipedia page. People walk by the outside of the genny and don't
even notice that it's on.

David Brady
'02 LXi, NC

-----Original Message-----

From: Stephen Birtles

Sent: Feb 21, 2009 11:16 AM

To: WanderlodgeForum@yahoogroups.com

Subject: [WanderlodgeForum] Re: Sound- absorption or reflection

if you look at the newer generators the sound deadening box has

baffled vents and is sealed as well as sound deadening

materials,thermostatically controlled fans and a smaller new motor

with indirect indirect injection. With all these it makes for a

quieter generator



Stephen 77fc35





--- In "WanderlodgeForum%40yahoogroups.com", Ernie Ekberg .>

wrote:

>

> Jim, while the some of the noise was deflected down, 30 more db was

reflected to the front of the radiator. Bob's coach has the front

fan/radiator.

>

>

> Ernie Ekberg

> 83PT40

> Wanderlodge

> Weatherford, Tx

> http://autos.groups.yahoo.com/group/erniesremodelingandrepair

>

> --- On Fri, 2/20/09, jim riordan wrote:

>

> From: jim riordan

> Subject: Re: [WanderlodgeForum] Sound- absorption or reflection

> To: "WanderlodgeForum%40yahoogroups.com"

> Date: Friday, February 20, 2009, 10:01 PM

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> I would assume that the sound deading material used in these

generator compartments actually reflect the nooise down. so the noie

is forced under the coaches. Many boats and I belive that some new

coaches now have a box lined with sound deading which the generator is

placed.

>

> just a thought

>

> jim riordan

> 88 wbwl xxv

> stuart fl

>

> --- On Fri, 2/20/09, Ernest Ekberg wrote:

>

> From: Ernest Ekberg

> Subject: [WanderlodgeForum] Sound- absorption or reflection

> To: WanderlodgeForum@ yahoogroups. com

> Date: Friday, February 20, 2009, 7:43 PM

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> After installing many generator compartments with the new insulation, I

> was wondering if there is a manufacturer that offers both.

> I insulated Bob Lawrences' generator compartment last December. He

> measured the db levels before and after and found that while the heat

> was reflected from the interior of the coach, the sound was also

> deflected to the outside. thus his db levels INCREASED to over 90.

> I know my with my coach, that I have been asked to park way downwind as

> my generator is really loud. Maybe its the dogs I carry with me???

> But, if there is a product that will absorb that sound while reflecting

> the heat, let's talk about it.

> Ernie-83PT40 in Texas, buying earplugs by the case~

>