dB Testing Thread

Discussion in 'Thumpers' started by meat popsicle, Jan 12, 2005.

  1. meat popsicle

    meat popsicle Ignostic

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    Hey y'all,

    dB testing is beginning. A big THANKS to dagwood for sending his very nice Quest Model 208 Sound Level Meter! :thumb We will be testing KTM 640 Adventures (LC4s) but dagwood would like to see more than just this one bike and the variety of pipes we have. I know of a few pipes that will be tested, Supertrapp IDS2 w/ race core (me), Supertrapp IDS2 w/ quiet core (PASSMORE), Akrapovics Ti (boejangles), and there could be others at LC4 Tech Daze at vrago's this weekend (stock?!?).

    A little bit of business to tend to first. The specs for testing are SAE J1169 Measurement of Light Vehicle Exhaust Sound Level under Stationary Conditions. This is THE standard, here and in Australia to name two places. Here is what I have on that test:

    Generally, the test looks for maximum dB (sound pressure) with the engine held steady at 75% peak HP.

    Here is the motorcycle specific setup, the Aussies throw in moving test specs as well, but their test is based on the ASE J1169:
    [​IMG]

    EDIT: So first question is: What's the RPMs at 75% of peak HP for a standard LC4? Later in the thread, vrago says 5250 :eek1 but that might be for his FCR/SXC piped bike. If you know your customized setup's HP curve, fine, otherwise lets use the stock LC4's curve. When somebody gets a chance please add this info somewhere. Thanks. :thumb

    Here is a exapmle dB testing sheet so that you can mimic the testing proceedures. Based upon this it looks like you take several readings (4?) and then average the highest two. Does anyone have the SAE J1169 test specs to check? They cost about $75 bucks from commercial outfits :eek1
    [​IMG]

    MORE BELOW
    #1
  2. meat popsicle

    meat popsicle Ignostic

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    ChrisC's link to a pdf of the SAE specs comes later. The pic above is the same stationary spec as the J1287 spec.

    Just a note here; I have seen a few different "interpretations" of the other test specs J1169, likely because its contentious and people want it to be what they want it to be... :nod

    One source (put in above) says the test speed should be the RPMs at 75% of Peak HP. Another says:

    "Noise levels will be checked from a twenty-inch distance from the exhaust pipe at half the vehicle's rated RPM or as detailed in the automotive specs SAE J1169, March 92 or SAE J1287, June 86."

    That is from an OHV site and is definately less conservative. It would be nice to know as this is the spec that the state uses in their new testing program. Anyone have it? I don't wanna spend $60 bucks to get that info from SAE.
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  3. meat popsicle

    meat popsicle Ignostic

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    SOUND FUNDAMENTALS
    Sound is defined as any rapid pressure variation in air (or
    other medium) that the human ear can detect. Because the ear
    can detect such a wide range of loudness from the softest of
    whispers to the din of jet engines, the decibel was adopted to
    express this range of sound levels. The softest sound a person
    can hear — the threshold of hearing —is, by definition, 0
    decibels (0 dB).

    The decibel is a logarithmic term such that sound pressure
    doubles every 6 dB. In terms of sound intensity or energy,
    sound doubles every 3 dB. Most industrial noise levels are
    thousands of times greater than the 0 dB level and will often
    be somewhere between 80 and 90 dB or louder. Nearby jet
    engines may produce sound levels up to 130 dB.
    The number of pressure variations per second is called the
    frequency of sound and is measured in cycles per second or
    Hertz (Hz). The human ear canhear very low frequencies down to about 20 Hz and can hear

    high frequencies to a maximum of 20,000 Hz. (The highest
    key on a piano is just over 4,000 Hz.) The 208 and 208L Sound Level Meters use a qualitymicrophone that detects sound in a similar manner to the
    human ear. The detected signal from the microphone is then "
    A "-weighted to give a response again similar to the way the
    ear responds. The noise is detected and averaged with a
    "SLOW" time constant to produce a display slow enough to
    be conveniently read.

    The measured sound depends not only on the loudness of the
    sound source but also on the distance from the source, the
    sound path, other sound sources, and the presence or absence
    of reflecting surfaces. The entire acoustic environment should
    be considered for the most accurate readings.

    Both meters are designed to be hand-held. When taking a
    measurement, hold the meter away from the body and other
    large surfaces and point it toward the sound source and
    upward at an angle of approximately 70° to the direction of
    sound.
    #3
  4. Frank Warner

    Frank Warner Traveller

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    The full description of the measured quanity is

    dBArel0

    You have covered

    dB though I think you fail to mention that it is a ratio - like %

    A

    but not the rel 0 - which means relative to 0 - the threshold of human hearing.

    Some measurements are made rel20 - untrasonics in particular.

    Think you will find the meter has a mounting for a camera tropod mount - on the base at the rear. I known the one I used does.

    --- OZ regulatons.... well some fool or two have given us 'ere in NSW as set of stationary tests ... and a sticker that we have to have on the bike.
    Basiclly - 0.5 m 45 degrees 0.2m height min and a max of 100dBArel0 for bikes before 1984, 94 for other bikes. And it is measured at 50% of the maximum horsepower speed of the engine. With the meter paralell to the ground. Link to test methos - stationary includes alarms, gresscutters, Mobile garbage compactors, chain saws etc.
    #4
  5. vrago

    vrago Plays with dirt

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    I'll be testing the KTM's sxc pipe.

    I have a tripod to use this weekend.

    If I get my shop cleaned up I'll print up a few record sheets.
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  6. Frank Warner

    Frank Warner Traveller

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    You should test in an open area - not inside like I did. :D If you test inside your readings will be higher. How much higher depends on the conditions :evil An open grassed area should give you the lowest readings.

    Wot I tried to do was use the standard configuration of K11 as a reference .. unfortunatly something is loose on the exhaust somewheres and rattles thus upping the noise. I've got to find that - fix it and retest. It will be a while before that gets done. I've got a roof that needs sweeping down before some bored kid on school holis starts playing with matches.
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  7. ChrisC

    ChrisC Amal sex?

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    Meat,

    Why not use the SAE J1287 test instead of the Aussie one?

    SAE J1287 is the defacto standard for motorcycle dB testing in the US.... :deal

    CC
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  8. dagwood

    dagwood Banned

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    the people that I have talked to that have been tested said the Forrest service Ranger has two setups and a book. The DB meter and a little pouch that he sets on the tank to measure RPM . the book tells the redline of a given bike and they test at half the redline RPM. IE if its a 8000 redline then they test at 4000 RpM
    easy...if you have a tach :rolleyes but how many thumpers have a tach? so my take on it is when they say max power output they realy mean RPM related power output.
    so it's gonna be a guestamit no matter how you do as the DB meter's vary as do the conditions tested.
    the FS Rangers have spendy units with a sponge like foam cover like a high end microphone over the head.
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  9. Frank Warner

    Frank Warner Traveller

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    That thing he sets on the tank will probably have a lead that clips over the spark plug lead - most bikes still have these. That does the rpm measurement for them.
    The epa test here too is half the rpm of max power (not the red line - that would be a bit higher). You certain the book is not rpm of max power?
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  10. dagwood

    dagwood Banned

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    No I'm not sure. just second hand info. your probably right about the leed wire.
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  11. meat popsicle

    meat popsicle Ignostic

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    Thanks Frank,
    My post directly above yours goes into dB in detail. Quote:

    "The decibel is a logarithmic term such that sound pressure
    doubles every 6 dB. In terms of sound intensity or energy,
    sound doubles every 3 dB. Most industrial noise levels are
    thousands of times greater than the 0 dB level and will often
    be somewhere between 80 and 90 dB or louder. Nearby jet
    engines may produce sound levels up to 130 dB.
    The number of pressure variations per second is called the
    frequency of sound and is measured in cycles per second or
    Hertz (Hz). The human ear canhear very low frequencies down to about 20 Hz and can hear high frequencies to a maximum of 20,000 Hz. "

    The post above that is the Aussie regulations for testing motorcycles.
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  12. meat popsicle

    meat popsicle Ignostic

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    According to SAE J1169 the test must be performed on hardscape (concrete etc) in order to be valid (mimics a roadway), must be performed outdoors, and with no object (save the meter and operator) within 3 meters of any side of the bike. Did y'all read the posts above? :D
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  13. meat popsicle

    meat popsicle Ignostic

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    Never heard of it Chris; SAE J1169 Measurement of Light Vehicle Exhaust Sound Level under Stationary Conditions is the only one I have seen cited as the test. Maybe that is a Colorado thing? In Cali, J1169 is the standard. Damn States Rights crap :lol3 Care to enlighten us?
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  14. meat popsicle

    meat popsicle Ignostic

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    The SAE J1169 specifies the revs to be held steady at 75% of peak horsepower. Since that is a difficult standard to meet in the field with modified bikes and poorly tuned bikes the FS must have made their own standardized test. I would argue that the FS test might be less stringent than the SAE J1169 standard; I am guessing that 4000rpm is a little low for 75% of peak HP. Anybody have the stock HP curves for the KTM 640 Adv?!? :ear
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  15. ChrisC

    ChrisC Amal sex?

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    Meat,

    SAE J1287 is a motorcycle specific, static sound test. It is accomplished at 20" from the pipe @ 45 degrees, engine at 50% of maximum rpm in neutral. Check the paper itself:

    SAE J1287

    Where's the Meatlette?
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  16. meat popsicle

    meat popsicle Ignostic

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    The lil' cutlette it still gestating; due date is saturday :D most first births happen after the due date w/in 11 days the midwife says. I almost bought a KTM baby suit but was too upset because they don't carry the KTM soothers anymore :baby :cry

    Now, dB testing... hmmm. J1287 that is very similar to the J1169 and should work well for our situation. One question: what is the stroke length of the LC4?

    Displacement, 625cc. Bore and Stroke, 101/78mm. Compression Ratio, 11.5:1

    If that is correct then the RPMs should be:

    250,000/78 = 3205 or 3200 for our purposes

    Everyone got that? The J1287 has a way to standardize the RPMs used. That works for me. I will send a copy of the SAE J1128 specs along with the unit.
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  17. ChrisC

    ChrisC Amal sex?

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    My stroke length is approximately 9.73 inches...does that help? :evil

    CC
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  18. meat popsicle

    meat popsicle Ignostic

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    WATCH YOUR UNITS!!! You must mean 9.73cm :nod :poser


    78mm? :ear
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  19. ChrisC

    ChrisC Amal sex?

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    Well, at least you didn't go for 9.73mm.... :eek1
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  20. meat popsicle

    meat popsicle Ignostic

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    Yeah, a moment of weakness... :evil


    Two questions:

    So 78mm is the stroke on a recent LC4? That is the number I found quickly. :ear

    And dagwood, for your Quest 208/L sound meter, the instructions are less than specific on what the scale means (I can't figure out what the lights are exactly). The Instructions (downloaded) say:

    "Example: With the range switch set at 70, if the 8 dB light is on, the level is 73 dB. If all the lights are on, the level is 90 dB or greater. If the zero dB light is on, the level is 70 dB or less."

    And that is all it says. :bluduh So if I can get an interpretation, here are the results from my bike (the number is the scale 70, 80, 90, 100 - and the +X is the LED number on the meter):

    03 KTM 640 Adventure
    Mods: Supertrapp IDS2 (race core) w/ 6 discs installed (pretty sure), open airbox, carb adjustments.

    Idle (1500 rpm) 80+2, 80+4
    3200 rpm (SAE J1287 Eq. A2) 90+6, 90+6
    4000 rpm 90+8
    5000 rpm 90+12
    6000 rpm 90+14

    at this point the monkey called an end to testing and my wife walked off so I only have one quickey run thru the higher revs. :eek1

    I also tested my new Hella Supertone dual horns (German model) and they were consistent at about 100+8 by putting the meter at the tip of the beak directly in front of the bike and pushing a few short blasts (1-2 seconds). I had to stop when the wife said, "What about the neighbors?". Agreed. It is pretty crappy if somebody works night shift. :nod

    If y'all could test the stock horn this way I would appreciate the comparison.
    #20