Return-Path: Sender: (Marvin Kaye) To: lml Date: Fri, 07 Mar 2003 10:01:12 -0500 Message-ID: X-Original-Return-Path: Received: from imo-d08.mx.aol.com ([205.188.157.40] verified) by logan.com (CommuniGate Pro SMTP 4.0.6) with ESMTP id 2046193 for lml@lancaironline.net; Fri, 07 Mar 2003 09:38:45 -0500 Received: from Sky2high@aol.com by imo-d08.mx.aol.com (mail_out_v34.21.) id q.60.2e4edab4 (30950) for ; Fri, 7 Mar 2003 09:38:28 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <60.2e4edab4.2b9a08e3@aol.com> X-Original-Date: Fri, 7 Mar 2003 09:38:27 EST Subject: Re: [LML] Lancair acoustic testing X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_60.2e4edab4.2b9a08e3_boundary" X-Mailer: 8.0 for Windows sub 830 --part1_60.2e4edab4.2b9a08e3_boundary Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Dan, Some observations about our composite aircraft and noise: Keep in mind that the following information is for a slow-built, Pre-preg=20 glass, thin canopied (3/16), 1989 Lancair 320 kit. =20 1. After the soundproofing described later, cruise flight (defined as 25=20 inches, 2500 rpm, 180 KIAS, Hartzell 70 inch CS prop) would yield between 10= 1=20 and 103 Db (slow response scale, Radio Shack noise meter). 2. The greater noise reading is obtained by opening the cockpit cooling=20 vents (air rush plus prop/engine). These are NACA ducts on the fuselage=20 sides at about 2 feet aft of the firewall that feed air at "calf" level and=20 thru an instrument panel "eyeball" vent just in front of each stick (face=20 air). 3. The measurements were taken near the pilot's right ear. 4. For comparison, my 96 Corvette yields a reading of 98 Db at 70 mph=20 traveling on asphalt pavement with 20,000 miles on the tires and not countin= g=20 the screams coming from the passenger. Sound conditioning components: 1. The interior is fully upholstered with sheepskin seats and various=20 automotive type wools over foam with "plastic" backing for shape control. =20 The baggage area below the waterline and the forward floors are carpet=20 covered. 2. The 18 pound E.A.R. soundproofing kit was installed. This consisted of=20 self-stick dense foam and dead aluminum coated sheets. 3. Material was applied to the back of the firewall and on the fuselage bac= k=20 to the seat backs, including under the seats and the nose wheel well. 4. The forward "D" section of the stub wing was soundproofed to eliminate a= =20 "sound-box" effect from that area. 5. Remember that the firewall consists of aircraft plywood, 2 sheets (in my= =20 case) of Fiberfrax and a sheet of stainless steel. The wood is a natural=20 sound barrier. Some conclusions drawn from a few experiments: 1. Most of the noise comes thru the 3/16ths inch canopy. I tried=20 soundproofing this, but it was hard to see out. Note that later kits were=20 supplied with =BC inch canopy material and that should go a long way to=20 reducing the noise transmitted thru the canopy. 2. The cockpit air intake's noise contribution would benefit from either a=20 quieter location or longer sound conditioned ducting. 3. If the baggage bulkhead is removed, one can hear a great deal of noise=20 from the tail cone. Don't fly without the baggage bulkhead in place. =20 4. Fiberglass is a hard surface and can reflect and enhance "noise". And, the ultimate conclusion is that you would have to pry my Bose headset=20 off of my cold dead ears - I will never give them up. I know the ES is a different animal and I applaud your use of lighter sound=20 conditioning material. I wonder if there is a light weight "flock" spray tha= t=20 could reduce noise or its reflection in unexposed interior areas? =20 Good Luck. Scott Krueger N92EX --part1_60.2e4edab4.2b9a08e3_boundary Content-Type: text/html; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Dan,

Some observations about our composite aircraft and noise:

Keep in mind that the following information is for a slow-built, Pre-preg gl= ass, thin canopied (3/16), 1989 Lancair 320 kit. 

1. After the soundproofing described later, cruise flight (defined as 25 in= ches, 2500 rpm, 180 KIAS, Hartzell 70 inch CS prop) would yield between 101=20= and 103 Db (slow response scale, Radio Shack noise meter).
2. The greater noise reading is obtained by opening the cockpit cooling ven= ts (air rush plus prop/engine).  These are NACA ducts on the fuselage s= ides at about 2 feet aft of the firewall that feed air at "calf" level and t= hru an instrument panel "eyeball" vent just in front of each stick (face air= ).
3. The measurements were taken near the pilot's right ear.
4. For comparison, my 96 Corvette yields a reading of 98 Db at 70 mph trave= ling on asphalt pavement with 20,000 miles on the tires and not counting the= screams coming from the passenger.

Sound conditioning components:

1. The interior is fully upholstered with sheepskin seats and various autom= otive type wools over foam with "plastic" backing for shape control.  T= he baggage area below the waterline and the forward floors are carpet covere= d.
2. The 18 pound E.A.R. soundproofing kit was installed.  This consiste= d of self-stick dense foam and dead aluminum coated sheets.
3. Material was applied to the back of the firewall and on the fuselage bac= k to the seat backs, including under the seats and the nose wheel well.
4. The forward "D" section of the stub wing was soundproofed to eliminate a= "sound-box" effect from that area.
5. Remember that the firewall consists of aircraft plywood, 2 sheets (in my= case) of Fiberfrax and a sheet of stainless steel.  The wood is a natu= ral sound barrier.

Some conclusions drawn from a few experiments:

1. Most of the noise comes thru the 3/16ths inch canopy.  I tried soun= dproofing this, but it was hard to see out.  Note that later kits were=20= supplied with =BC inch canopy material and that should go a long way to redu= cing the noise transmitted thru the canopy.
2. The cockpit air intake's noise contribution would benefit from either a=20= quieter location or longer sound conditioned ducting.
3. If the baggage bulkhead is removed, one can hear a great deal of noise f= rom the tail cone.  Don't fly without the baggage bulkhead in place.&nb= sp;
4. Fiberglass is a hard surface and can reflect and enhance "noise".

And, the ultimate conclusion is that you would have to pry my Bose headset o= ff of my cold dead ears - I will never give them up.

I know the ES is a different animal and I applaud your use of lighter sound=20= conditioning material. I wonder if there is a light weight "flock" spray tha= t could reduce noise or its reflection in unexposed interior areas? 
Good Luck.

Scott Krueger
N92EX
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