X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-yh0-f42.google.com ([209.85.213.42] verified) by logan.com (CommuniGate Pro SMTP 6.0.8) with ESMTPS id 6735445 for flyrotary@lancaironline.net; Sun, 16 Feb 2014 20:39:50 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.213.42; envelope-from=ceengland7@gmail.com Received: by mail-yh0-f42.google.com with SMTP id a41so13849255yho.1 for ; Sun, 16 Feb 2014 17:39:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type; bh=epkHaKvowSH96jjar31WOBAPkEoPepXR88fnq+TPakY=; b=W2Rw/T46aK9uu4BwAK7zWQdTWim4sRtjopH2tbcK/MHpWNMOf7B/Z0XEPBef3Oujdn f1LOrmLl/GMlkCTrksP67nZJi5L9OdPiFUZgDgPodvzKE1UrvATeB+39hxXF/fx1mMIX anshA5jSTQdwwq+ITrnd8ftnUfpQH1hULpSvIUvbzvLIxB2+Xyq768RAKTWjf+I5BZBw 9Ix98ByEGlpbr7xTD1FViS+wSEjmoDQ7I0xh1IOiIyzOGbQk+J/a4jLDICbCl28+YTTh Z9vTfVm+e3zOuFqZ1XYYfzN6LLoY2U0Lmg1MaKTgu7iMc1f2D7l2g0BT89iosmiTiVbQ Ix7w== X-Received: by 10.236.152.233 with SMTP id d69mr23475251yhk.11.1392601157397; Sun, 16 Feb 2014 17:39:17 -0800 (PST) Return-Path: Received: from [192.168.10.36] (adsl-98-95-183-178.jan.bellsouth.net. [98.95.183.178]) by mx.google.com with ESMTPSA id g25sm43412893yhg.6.2014.02.16.17.39.15 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 16 Feb 2014 17:39:16 -0800 (PST) Message-ID: <5301687E.6060503@gmail.com> Date: Sun, 16 Feb 2014 19:40:14 -0600 From: Charlie England User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Sound Level Testing References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------060200010100080808070404" This is a multi-part message in MIME format. --------------060200010100080808070404 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 2/16/2014 4:09 PM, shipchief@aol.com wrote: > I bought a Wensn 30-130 Decibel sound meter off fleabay. I use it to > record sound levels in front of my face in flight. > I first tested my RV-8 after installing a turn down tip, but was also > experiencing severe exhaust leaks from my turbo: 19.7 DBa > After fixing the leak, I recorded 16.8 DBa > Then I squeezed the turn down tip to a flattened rectangle opening, > and replaced the lost area with 1/4" holes, which I bent to face > backwards with a Philips screwdriver. a Piccolo Pipe, as it's known. > Kind of a cheese grater for sound waves. Next reading: 14.6 DBa > This is still to loud for my worn out ears, so I bought an Aeroturbine > 2525 muffler, as described on this forum. I've been collecting 304 > stainless pipe bend, ball joints clamps and hangers. I hope to get > something cobbled together this weekend. > I have a 2" exhaust pipe from the turbo which discharges aft. The pipe > has 2 90 degree bends and exhausts in and parallel to the exit air > ramp on the bottom. I plan to use the Ford type exhaust hangers with > 3/8" rods. > I, too, am looking forward to your report on how well it works. Suggest checking what's going on with your dB readings, though. 16 dB is quieter than a bedroom at night, & likely inaudible to those of us who have been flying for a decade or two. Realistic levels expected in the cockpit of a homebuilt will be between 85 dB (pretty good, but still loud) & 120 dB (loud rock concert levels and painful to most of us). I'd also suggest using the C scale instead of the A scale. The A scale is very commonly used, but it presents a very distorted view of the actual sound level. It radically filters the low end of the spectrum, and to a lesser extent, the high frequencies, as well. It will mask the level of your actual noise exposure, especially at the low end of the noise spectrum. Charlie --------------060200010100080808070404 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
On 2/16/2014 4:09 PM, shipchief@aol.com wrote:
I bought a Wensn 30-130 Decibel sound meter off fleabay. I use it to record sound levels in front of my face in flight.
 I first tested my RV-8 after installing a turn down tip, but was also experiencing  severe exhaust leaks from my turbo: 19.7 DBa 
After fixing the leak, I recorded 16.8 DBa
Then I squeezed the turn down tip to a flattened rectangle opening, and replaced the lost area with 1/4" holes, which I bent to face backwards with a Philips screwdriver. a Piccolo Pipe, as it's known. Kind of a cheese grater for sound waves. Next reading: 14.6 DBa
This is still to loud for my worn out ears, so I bought an Aeroturbine 2525 muffler, as described on this forum. I've been collecting 304 stainless pipe bend, ball joints clamps and hangers. I hope to get something cobbled together this weekend.
I have a 2" exhaust pipe from the turbo which discharges aft. The pipe has 2 90 degree bends and exhausts in and parallel to the exit air ramp on the bottom. I plan to use the Ford type exhaust hangers with 3/8" rods.
I, too, am looking forward to your report on how well it works.

Suggest checking what's going on with your dB readings, though. 16 dB is quieter than a bedroom at night, & likely inaudible to those of us who have been flying for a decade or two. Realistic levels expected in the cockpit of a homebuilt will be between 85 dB (pretty good, but still loud) & 120 dB (loud rock concert levels and painful to most of us).

I'd also suggest using the C scale instead of the A scale. The A scale is very commonly used, but it presents a very distorted view of the actual sound level. It radically filters the low end of the spectrum, and to a lesser extent, the high frequencies, as well. It will mask the level of your actual noise exposure, especially at the low end of the noise spectrum.

Charlie
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