Science Experiment.

[lynnm]

LOL

I bought a Radio Shack analogue SPL meter this weekend. I discovered that average listening for me was generally in the 70db range and that 100db was louder than I really like. I was hitting 106db at times and my hearing aids were clipping.

Intellectually, I essentially understand the relationship between acoustic db levels and amplifier power ratings but until I actually heard an honest 100db average output I had never really understood/knew what that really meant.

As the late Fritz Perls ( Psychologist and father of Gestalt Therapy) said....... There is Knowing and There is KNOWING.

In a similar vein:

I understand enough of physics to understand how a large jet aircraft can fly once it's up there but every time I fly I find myself astonished that anything as big and heavy as a jet airliner can accelerate that fast on takeoff !

Jet engine power is always expresed in terms of thrust. Can anyone supply a rough estimate as to the horsepower equivalent of the thrust of say a 767 on a take off roll ?

I don't need to know....but I would love to know.

[edwinr]

Same here. I just bought the Radio Shack spl meter. I was really surprised that 90db in my very large room was loud! I am trying to imagine what the Klipschorns will sound like at 120db!

[3dzapper]

LOUD!!!!!!!!!!!!!!!!!!!

Been there done that! If I do that any more I will need to borrow Lynn's hearing aids. My normal listening level is between 85 and 90Db. On special occasions I'll play an album at 100+/-.

Rick

PS: Lynn I used to know the horsepower equivelant of a fighter jet but it escapes me at the moment.

[scriven]

The easy answer is damn loud! It doesnt matter what speakers they are, except maybe the Khorns will have less distortion than others, 120db is considered the threshold of pain. (And is where hearing damage is a real possibility if not probability.) At that level the pain is not due to distortion!

[edwinr]

Yeah but what a way to go.......

[3dzapper]

A jet engine operates on the application of Sir Isaac Newton's third law of physics: for every action there is an equal and opposite reaction. This law is demonstrated in simple terms by releasing an inflated balloon and watching the escaping air propel the balloon in the opposite direction. In the basic turbojet engine, air enters the front intake and is compressed, then forced into combustion chambers where fuel is sprayed into it and the mixture is ignited. Gases which form expand rapidly and are exhausted through the rear of the combustion chambers. These gases exert equal force in all directions, providing forward thrust as they escape to the rear. As the gases leave the engine, they pass through a fan-like set of blades (turbine) which rotates the turbine shaft. This shaft, in turn, rotates the compressor, thereby bringing in a fresh supply of air through the intake. Engine thrust may be increased by the addition of an afterburner section in which extra fuel is sprayed into the exhausting gases which burn to give the added thrust. At approximately 400 mph, one pound of thrust equals one horsepower, but at higher speeds this ratio increases and a pound of thrust is greater than one horsepower. At speeds of less than 400 mph, this ratio decreases.

I just did a Google search. An F-4 Phantom with 2 GE J79 jet engines developed 90,000 BHP at sea level with afterburners lit.

Here is the data for a 767:

Specifications

Wingspan 47.6m

Length 48.5m

Height 15.9m

Seating 234seats

Gross Weight 120,900kg

Maximum Speed 880km/h(M0.80)

Altitude capability 13,100m

Range 4,040km

Take off Distance

Landing Distance 1,540m

1,610m

Fuel Capacity 45,900

Power Plant General Electric

CF6-80A

Engine Horsepower 21,770kg x 2

21,770*2.2*2=95,788 horse power!

Rick

[lynnm]

What ??

Que??

Speak up and take the marbles out your mouth you whelp !!

[3dzapper]

The best thing about klipsch speakers besides there dynamic range and clarity is never having to say:

I CAN'T HEAR YOU!!!!!!!

Even with a SET amp.

[Deang]

Again, 100db coming out of a 10 watt amp doesn't sound much like a 100db coming out of 40 watt amp. The latter will not drive you out of the room, but the former might. Also, 100db steady state is brutally uncomfortable, where 90db steady state with peaks hitting 100db sounds pretty good to me.

[edwinr]

Yes I noticed that. I was setting up a friends home theatre system comprising of Onkyo receiver, m&k thx 150 sub and Reference series speakers in a medium sized room, well furnished. I utilised my new spl meter and at dolby reference 75 db using pink noise - it was loud!

[hwatkins]

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On 6/29/2004 12:01:44 AM AK-4 wrote:

Again, 100db coming out of a 10 watt amp doesn't sound much like a 100db coming out of 40 watt amp. The latter will not drive you out of the room, but the former might. Also, 100db

steady state

is brutally uncomfortable, where 90db steady state with peaks hitting 100db sounds pretty good to me.

----------------

Wow - I set up my systems with a reference level of 85db and I have tried to run at that steady (kind of) state 90db and I am not able to maintain an enjoyable experience past 30 minutes or so. When I a similar volume poolside I am estatic.

Probably these older ears have something to do with it...nah, can't be my fault

[D-MAN]

I have no idea the SPL (on corner horns) that I usually listen to, except that the "watt" meters on the front of my amp (granted, not very scientific) average about 1/3 watt. I presume that the peaks may be upwards of that, but the needles stay at or below 1/3 watt...

Anything above that is uncomfortable. I only go past that to "show off"...

DM

[mark1101]

OK, this is a perfect week for me to try out this stuff. I too like Lynn have never measured SPL. But I have had Klipsch Heritage products for 25 years and trust me they get used more than adequately. It would be nice to know how hard I have been using them.

How much is a Rat Shack SPL meter? Any particular model more useful than another?

Thanks

[mike stehr]

The Rat Shack SPL meter rolls off at about 12kHz, and about 30 Hz.( I think...)

http://www.gti.net/wallin/rsmeter.htm

Modifications for the RS SPL meters.

[gtDark]

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On 6/28/2004 11:42:28 PM 3dzapper wrote:

A jet engine...

----------------

That's hot.

[Marvel]

The last place I worked now markets a real jet turbine engine for model planes. It is only about 12 inches long and 8 inches in diameter. You still need hearing protection to be around it while it is running. The plane we had one in would do about 130 mph. Needles to say, they can get out of range of your radio gear pretty quickly at that speed.

http://www.usamt.com/

They have a video of one of the planes flying. I had worked for AAC doing computer support, and helped do wiring harnesses.

They also have a video of a glider with two of the small engines on it with some guy flying it, not R/C but in the thing. Two engines at 45 lbs of thrust each. Way cool.

Marvel

[WMcD]

I'd like to throw in my vote for what Lynnm is saying.

People read about, say, 100 dB without having the objective measuring tool to tell them that "this IS 100 dB" from which they can reach a subjective opinion. Even 90 dB is darn loud.

The psychologist may be descibing the same. One may read about experiences all they want and thinking that more reading makes one an expert. Not so. You have to do it yourself.

I had written about the standing wave phenomenom (sp) in a similar way. You can get some software to turn your computer into a tone generator and feed constant frequencies to your speakers at a careful level. Moving around the room you can find nulls where the speaker output becomes silent.

Unless you do this for yourself, you'll never really believe the effects of "the room" on frequency response.

Gil

[formica]

Our sensitivity (and annoyance) to sound varies with frequency... and in general we can endure louder low frequency sounds versus higher frequency ones. That is why white and pink noise can be so annoying... yet a 30Hz tone will make you feel fuzzy inside.

As gil mentioned, the first time I tried a test tone disk (I didn't have a SPL meter at the time) I was very impressed/astonished by the variances caused by room effects. We are talking of 20db variances between peeks and nulls at different frequencies! VERY noticeable.

Once you've experimented with pink noise and test tones, you should also try a music source... you'll see as AK4 mentioned, music dynamics vary quite a bit and is enjoyable at higher SPL. For example, 110db to 115db peaks can be quite exciting to me...

Later...

Rob

PS: BTW, the RS meter does not have a flat response versus frequency, but there are commonly available correction factors which will approximate one. It's accurate enough to measure general room response... but it isn't a substitute for a calibrated mic.

[edwinr]

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On 7/1/2004 12:53:59 AM formica wrote:

Our sensitivity (and annoyance) to sound varies with frequency... and in general we can endure louder low frequency sounds versus higher frequency ones. That is why white and pink noise can be so annoying... yet a 30Hz tone will make you feel fuzzy inside.

...and the sound of water dripping out of a tap at night. It's so annoying. For fun I tried to get a reading from my spl meter from a couple of feet away, it hardly registered.

[Schurkey]

Living in the Frozen Wastelands, I've become a College Hockey fan. Our local arena (a $100,000,000 alumni donation, half of which was supposedly earmarked for academics but was then "stolen" to complete the arena.) has 50,000 watts of amp power, and more giant PA speakers than you can shake a stick at.

http://theralph.com/new2/Arena_Info_Section/VirtualTour.htm

Typical SPL readings with my RS analog meter hover around 100 db. (for two+ hours!) I've seen 110 db peaks. Not only is it TOO FRIGGIN' LOUD, but you can't understand what they're saying about 10% of the time. My wife, in-laws, and I have to wear hearing protection ear muffs to sit through a game. You should see the infants crying, and kids plugging thier ears with their fingers. Tragic, preventable, and as might be predicted, arena management ABSOLUTELY REFUSES to respond appropriatly. They use sound pressure as a crowd control tactic: Whenever they want "home team advantage" the volume goes even higher, to agitate the masses into a frenzy. AND IT WORKS! The volume hits 110 db and the crowd goes nuts. I see this every game. (Granted, it's kind of circular: As the PA volume goes up, so does crowd noise. It becomes kind of a feedback loop, once started it just builds on itself.)

I consider this overwhelming evidence that spending tons of money on amps and speakers is TOTALLY WASTED if (1) you choose expensive yet crappy equipment, and (2) the doofus at the control board doesn't care about sound quality.

Translated into a home environment: Don't be a doofus when setting up and operating your equipment!