Reducing engine noise is just like teenage sex:
* Everyone is talking about it
* A few are really doing it
* The ones doing it think it should be
* The ones not doing it
wish they were
The difference between teenage sex and reducing engine noise is that everyone
should be doing it.
Like IT though, reducing engine noise on a motor rig is not something you go
out and do right the first timeit is a learned art. Before you start
doing it, you need a level of commitment because it is not that easy. For some time now, I
have been trying to figure this thing out (the noise thing, that is), and I have come up
with some things that seem to help. But there is still a long way to go.
How you reduce the noise level is not the issue hereit is the WHY . In
1996, the Park will be developing a new River Management Plan, and at the same time, will
be looking at wilderness designation for the entire Park. You can bet your spare prop that
the motor issue will be one of the hot spots, especially when added to what seems to be
happening with aircraft noise (see Jeris overflight article). We cant afford
not to start doing something now. If we wait until 1996, it will be too late.
This is not an easy thing to do, but its not insurmountable either.
From a technological standpoint, it is far less complex than the aircraft noise problem
and we cant just float along bitching about overflight noise and not clean up our
The National Park Service has a standard of 60 decibels at 50 feet as an
acceptable noise level for recreational vehicle generators, and that should be our target.
Granted, it is a small target, but the rewards for everyone are tremendous when we hit it.
There are a lot of factors involved in reducing noise levels. But they really
fall into three categories: the engine, the boat, and the driver. There is not much we can
do about the inherent noise level of the 2-cycle engines most commonly used in the canyon,
other than beat on the manufacturers to make them quieter. And we should, because there
are things they can do. There are also things we can do to absorb some of that noise
before it leaves the engine. Some companies are already doing it. For example, Arizona
River Runners just lined their engine covers with a lead-lined foam that results in a 4 db
noise level reduction. It brings the noise level at the drivers ear down to 93 db, and 69
db at mid boat. Its not at RV generator levels, but it is a start. Other companies
are doing things as wellwe have towe cant just sit back and wait for the
manufacturers to act or the park to mandate.
Several companies and the Park have looked at 4-cycle engines. They are
quieter, but I dont think they are the answer. Being a 4-cycle engine means more
moving parts, which translates to harder to tune and less reliable. Their power curve is
slower to react to the throttle and they are heavy. (A 2-cycle Johnson 30 HP is 115 lbs
and the 4-cycle Honda 30 HP is 138 lbs). In some applications, this could be the answer. I
Boat design is something we can do something about. It is no secret that an
open stern boat results in more noise trailing behind than a closed stern boat, although
there is probably no difference to the driver or the passengers.
The jackass that most companies use was designed for utility, not for their
noise dampening potential.
In many cases, the boat frames act just like big amplifiers, converting the
vibration from the engine into noise. They need to be examined for vibration absorbing
potential as well.
A few rowboatmen have told me that GCEs boats are the quietest on the
river. Im not sure if or why thats true. But, if it is, it is probably many
little things adding up an overall system that works. Or maybe their boatmen are better
about it than the rest of us.
The boatman is the biggest factor and probably the hardest to fix. They have
almost complete control of the noise the engine produces. We cant just leave it off
all the time, but we dont have to run full throttle all of the time either. We (me,
too) need to consider the impact we have on others as well as on our own folks.
Approaching a row trip and shutting down to float with them for a few minutes may not be a
bad idea for everyone involved, boatman and passengers.
One of the things that makes this such a complex issue is that what works on
one boat, may not work on the next. But we need to start exchanging ideas. This is an
industry wide problem, not a company problem.
Well, Ill get off my soapbox for now. If you are interested in some of
the things that we have found that work, give GCRG a call, and ask for a copy of The
Noise Letter. If you have any ideas, questions, or want to talk about it, leave me a
message at (602)585-6943. Ill get back to you.