Sound levels of modern skiboats

Sound levels of modern skiboats

Post by To » Sat, 15 Feb 2003 17:32:48


Hello,

at the lake we're skiing home owners appear to strive to ban skiing.
One of their many reasons they want to ban skiing is the sound
skiboats produce. The city council is sensitive for their complaints
and we have to fear that we are going to be forced to move the slalom
course more to the middle of the lake. Currently we are already 80
meters out of shore, and since this is windy Netherlands, windforce
4-5 is enough to make the slalom course too choppy to perform.
Increasing the distance from the shore to the course is therefor not
an option for us.
To oppose moving the slalom course more to the middle of the lake I
would like to make a statement for the city council that the amount of
sound produced by skiboats is nowadays not "too bad" anymore, thus
questioning the justification of the complaint about the produced
sound.
I think I have three arguments to support this:
1. Number of speeds licences has gone down over the years by almost
40%. Just a fact.
2. Distance from shore to slalom course increased some years ago from
50 to 80 meters. Also just a fact.
3. Sound levels of skiboats have gone down considerably.

To support this last issue I'm looking for information on:
a. a comparison on sound levels of skiboats (now and 10 - 15 years
ago(i.e. before the improved sound mufflers were introduced)). This
info is required to imply that home owners already have received a
sound reduction because of improved technology.
b. the amount of sound produced by a modern skiboat at various
distances (like 25 - 50 - 75 - 100 - 125 m) measured. This info is
required to support that most sound reduction has already been
attained in earlier days by increasing the distance from the shore to
the course from 50 to 80 meters and (hopefully) not so much more can
be gained anymore by increasing the distance another 25 - 50 meters.
Note that sound levels measured at the typical 1 m from the exhausts
is not what I am looking for since such figures do not reflect the
sound level the home owners have.

Any idea where I can find this kind of info ?

Greetings,

Tom

 
 
 

Sound levels of modern skiboats

Post by Tom Rut » Sun, 16 Feb 2003 00:10:49



...

Quote:
>Any idea where I can find this kind of info ?

www.iwsf.com They have a technical paper addressing this kind of
thing.

Tom

 
 
 

Sound levels of modern skiboats

Post by Reg » Sun, 16 Feb 2003 05:31:13

I'd start with the manufacturers, they would probably be PROUD to show
their noise reduction curves over the years.  I have one of the early "quiet"
boats a '90, that was nick named "Stealth" by the lake residents who would wake
up and look out only to see that we were about finished.

The distance issue is probably against you, ANY increase in distance is going
to reduce noise perceived at shore.  In still air it is an inverse square law
relationship, e.g. 2 times the distance == 1/4 the sound pressure, 3 times ==
1/9
etc.  with wind I'd guess the reduction is even greater.

I'd stick with the "we already moved from 50m to 80m  - resulting in a
(do the math) % reduction"  and  "manufacturers data shows the following
reductions due to product improvements"  but be careful with that if you
have some > 15year old boats out there, they might start a fight to ban
boats over some arbitrary age.  If that gets you spousal permission
to update your vessels, may not be too bad after all (-:

\R

 
 
 

Sound levels of modern skiboats

Post by Marc Karstaed » Sun, 16 Feb 2003 09:29:07

AWSA tests sound levels as part of their certification. See page 15 of this
document:

http://www.usawaterski.org/downloads/2002towboatmanual.pdf

for their criteria.

Basically an AWSA approved tournament boat will not exceed 75 d(B)A for
either
36 or 34mph passes.


Quote:
> Hello,

> at the lake we're skiing home owners appear to strive to ban skiing.
> One of their many reasons they want to ban skiing is the sound
> skiboats produce. The city council is sensitive for their complaints
> and we have to fear that we are going to be forced to move the slalom
> course more to the middle of the lake. Currently we are already 80
> meters out of shore, and since this is windy Netherlands, windforce
> 4-5 is enough to make the slalom course too choppy to perform.
> Increasing the distance from the shore to the course is therefor not
> an option for us.
> To oppose moving the slalom course more to the middle of the lake I
> would like to make a statement for the city council that the amount of
> sound produced by skiboats is nowadays not "too bad" anymore, thus
> questioning the justification of the complaint about the produced
> sound.
> I think I have three arguments to support this:
> 1. Number of speeds licences has gone down over the years by almost
> 40%. Just a fact.
> 2. Distance from shore to slalom course increased some years ago from
> 50 to 80 meters. Also just a fact.
> 3. Sound levels of skiboats have gone down considerably.

> To support this last issue I'm looking for information on:
> a. a comparison on sound levels of skiboats (now and 10 - 15 years
> ago(i.e. before the improved sound mufflers were introduced)). This
> info is required to imply that home owners already have received a
> sound reduction because of improved technology.
> b. the amount of sound produced by a modern skiboat at various
> distances (like 25 - 50 - 75 - 100 - 125 m) measured. This info is
> required to support that most sound reduction has already been
> attained in earlier days by increasing the distance from the shore to
> the course from 50 to 80 meters and (hopefully) not so much more can
> be gained anymore by increasing the distance another 25 - 50 meters.
> Note that sound levels measured at the typical 1 m from the exhausts
> is not what I am looking for since such figures do not reflect the
> sound level the home owners have.

> Any idea where I can find this kind of info ?

> Greetings,

> Tom