[C320-list] Engine compartment sound proofing - Some preliminaryresults

[Kaare Wold]

Thanks Ken, your report is certainly valuable and detailed.   Many thanks to 
all the other contributors to this thread.  This collection of data and 
information really helps and confirms what a great group this is.
Kaare Wold   Sheet Music  #945 on foggy Lake Michigan.
----- Original Message ----- 
From: "Ken Danko" <320kend at att.net>
To: <C320-List at Catalina320.com>
Sent: Tuesday, June 24, 2014 7:30 PM
Subject: [C320-list] Engine compartment sound proofing - Some 
preliminaryresults


> Hi all:
>
> I have wanted to install engine soundproofing for years and the recent 
> discussion here motivated me to finally make the move. I took Jeff's 
> suggestion and this morning I went to West Marine and bought their kit: 
> $155 including our very high sales tax. I was disappointed to find that 
> there wasn't enough material to fit both of the covers. There was enough 
> for the front cover and probably the top of the rear cover.
>
> Before I started the job I decided to measure the sound levels with my 
> iPhone. So here are the details on that. I have an iPhone 4s running the 
> latest operating system. The free app I used is called dB Volume; I didn't 
> change any of the default settings. I set the iPhone on the outer curved 
> edge of the dinning table, face up , with a 1/2 inch overhang, and with 
> the microphone facing the engine. I first measured the background noise 
> without the engine running: 42 dB. I then started the engine and ran it at 
> 1500 RPM (admittedly an arbitrary speed).  With the existing engine cover 
> on and the steps down and the companionway open I got a reading of 71 dB. 
> Then I took the front cover off just to see what the sound level would be: 
> 80dB.
>
> I spent a couple of hours meticulously cutting and installing the 
> soundproofing material on the inside of the front cover. I made sure that 
> there were no gaps and I taped all the ends. I had to cut out a half-moon 
> shape (1/4 inch deep) in the middle to accommodate the flywheel. I taped 
> over this area with the metal tape provided in the kit. I have to say, it 
> looks great.
>
> I know that I need to do the back cover to experience the full effect but 
> I wanted to see how much sound reduction I would get from my day's work so 
> I started up the engine and set it at 1500 RPM again. I was delighted to 
> hear the engine, which, to my untrained ears, sounded quieter both in the 
> cockpit and below deck. But then I set about measuring the resulting sound 
> level with my iPhone. Guess what? 71 dB!!! So much for my own judgement 
> about sound! I turned the engine off and re-checked the background noise 
> level, it was still 42 dB.
>
> I realize that I am going to have to buy some more material to do the back 
> cover and I am exploring alternatives to West Marine. I will report back 
> to the group when I finish the project. But I have to say, I'm pretty 
> disappointed so far. It was a gorgeous day here and as I drove home I 
> looked out over the bay and thought about how I could have spend the day 
> sailing instead of installing sound proofing that did nothing to reduce 
> the sound levels.
>
> Ken Danko
> "Grace"
> San Francisco
>