Sound

[serautoxer]

Here is a link to a very informative report about sound issues.

I have not read the entire thing yet, but it looks to be good reading.

http://www.flowmastermufflers.com/sound_management.html

[woodrufj]

Lot of good stuff. Here's a couple inaccuracies I noticed though.

"A "Radio Shack" brand sound meter is undeniably inexpensive, but its accuracy is not sufficient for racetrack needs and it cannot be calibrated."

The Radio Shack meter can be calibrated. It just doesn't hold a cal like certified meters do.



"Every 6 dB increase, is a doubling of sound pressure, this also holds true for reductions in sound. EXAMPLE: 100 dB - 6 dB = 94 dB, which equals a 100% reduction in sound pressure!"

Every 3dB is a 'doubling', not 6. A 100% reduction in sound pressure would result in no sound.

Jay W
505/287 Dakota

[MX5bob]

Lot of good stuff. Here's a couple inaccuracies I noticed though.

"A "Radio Shack" brand sound meter is undeniably inexpensive, but its accuracy is not sufficient for racetrack needs and it cannot be calibrated."

The Radio Shack meter can be calibrated. It just doesn't hold a cal like certified meters do.



"Every 6 dB increase, is a doubling of sound pressure, this also holds true for reductions in sound. EXAMPLE: 100 dB - 6 dB = 94 dB, which equals a 100% reduction in sound pressure!"

Every 3dB is a 'doubling', not 6. A 100% reduction in sound pressure would result in no sound.

Jay W
505/287 Dakota

A lot of people don't understand that percentages and logorithms don't get play well together.

[woodrufj]

A lot of people don't understand that percentages and logorithms don't get play well together.
Yeah, but that's an easy one. If I took 100% of your apples, you'd be hungry.

They just got confused that a 100% increase is a doubling, but then a 50% decrease is a halfing.

Jay W
505/287 Dakota

[RandyC]

The interesting points I read was the thing about body reflections from the person doing the monitoring (microphone must be away) and that the prefered placement should be 4' off the ground... and the potential impact of more than one car on course.

I know based on how our courses are, that multiple cars will not be that great of an impact, but I wonder if there is still some measurable change? It would also add one more reason why a test course before a Tour (one car on course mostly) can be a lower reading than at the Tour (3-4 cars on course).

[woodrufj]

"Measurable" is very sensitive. The differance between 93 and 93.1dB is, I forget how to do the math right now, but the differance is tiny. Nature of a dB scale. So a second car somewhere on course could tip you over. But, if you're counting on that 93 not tipping to a 93.1, you ridding a very, very thin line.

But this goes both ways. The differance between 90 and 93 is fairly large. If you're car runs 90 and another equally loud car decides to leap frog you at the same time you pass the meter theoritically you'll only hit 93.

I'd say most sound reading differance come from different cars being at different RPM levels when they go through the measurement zone. The only solution I can think of is to fix the meter and the measurement zone of the course (which includes the turn before the measurement zone and maybe the turn after) from the "test" course through both days of competition, and hope the weather doesn't change too much. Unfortunetly having people pre-run a portion of the real course is a pretty big no-no in solo2 competition.

Jay W
505/287 Dakota

[mievil]

"Measurable" is very sensitive. The differance between 93 and 93.1dB is, I forget how to do the math right now, but the differance is tiny.

Hate to dig into this to much, but just because.....I believe that the 0.1dB would be an increase of 1.259. :)


****Edit: forgot to divide by 10. Should be 1.023, not 1.259.)

[MX5bob]

Hate to dig into this to much, but just because.....I believe that the 0.1dB would be an increase of 1.259. :)

1.259 what? as a factor?

[woodrufj]

1.259 what? as a factor?
Definitly not a factor. Probably a % increase.

Jay W
505/287 Dakota

[mievil]

Multiplication factor. (however I forgot to divide by 10.)

Just as 3dB is a multiplier of 2,

10db would be a multipler of 10,



With 10s (10, 100, 1000, 0.1, etc) it's basically a multiplier of 10 superscript x, where x would be the dB delta divided by 10. 10dB higher would be 10 superscript 1, so a multipler of 10. 0.1dB would be 10 superscript 0.01 which would be a multiplier of 1.023.

***Edited due to a mistake.***


So 0.1dB difference should be 1.023 times higher.

I hope this is right.

[nalbar]

ok guys,



go get back under your rocks.



nalbar

[Bimota Guy]

Multiplication factor. (however I forgot to divide by 10.)

Just as 3dB is a multiplier of 2,

10db would be a multipler of 10,



With 10s (10, 100, 1000, 0.1, etc) it's basically a multiplier of 10 superscript x, where x would be the dB delta divided by 10. 10dB higher would be 10 superscript 1, so a multipler of 10. 0.1dB would be 10 superscript 0.01 which would be a multiplier of 1.023.

***Edited due to a mistake.***


So 0.1dB difference should be 1.023 times higher.

I hope this is right.
Correct, which is far below the threshold of hearing a difference.

The important thing to not lose sight of is that about a 2-3dBA difference is merely the threshold of being able to hear a difference in sound. Too many people harp on the math which gives a false impression. People often say things like, "My car could not possibly be twice as loud as it used to be", when they go from about 90 to about 93. About 10dBA is where humans perceive that the sound is about "twice as loud."

[mievil]

ok guys,



go get back under your rocks.



nalbar


Sorry. :p

[woodrufj]

What he meant to say was,

numbers no like warren, numbers make warren head hurt

nalbar

[nalbar]

HeHe,

or like they say at work,

"Flaco no likey"



nalbar

[leaftye]

Every 3dB is a 'doubling', not 6. A 100% reduction in sound pressure would result in no sound.

Jay W
505/287 Dakota

I'm either not familiar with the term you're using, or you're wrong. To our ears, it takes a 6-10 dB increase to "sound" twice as loud. Notice that it's subjective due to the sensitivity of the listener. Now if you mean it takes twice as much power to create a 3 dB increase, then you'd be absolutely correct. If you're having trouble understanding this, go to the JBL website and the JBL Professional Sound System Design Manual, Part I....then go to page 15.

Here's a clip:

The following tabulation illustrates the
usefulness of the concept. Letting P0 = 1 watt:
P1 (watts) - Level in dB
1 - 0
10 - 10
100 - 20
1000 - 30
10,000 - 40
20,000 - 43
Note that a 20,000-to-1 range in power can be
expressed in a much more manageable way by
referring to the powers as levels in dB above one
watt. Psychoacoustically, a ten-times increase in
power results in a level which most people judge to
be Òtwice as loud.Ó Thus, a 100-watt acoustical signal
would be twice as loud as a 10-watt signal, and a
10-watt signal would be twice as loud as a 1-watt
signal. The convenience of using decibels is
apparent; each of these power ratios can be
expressed by the same level, 10 dB. Any 10 dB level
difference, regardless of the actual powers involved,
will represent a 2-to-1 difference in subjective
loudness.

[Bimota Guy]

I'm either not familiar with the term you're using, or you're wrong. To our ears, it takes a 6-10 dB increase to "sound" twice as loud. Notice that it's subjective due to the sensitivity of the listener. Now if you mean it takes twice as much power to create a 3 dB increase, then you'd be absolutely correct. If you're having trouble understanding this, go to the JBL website and the JBL Professional Sound System Design Manual, Part I....then go to page 15.
If you would have bothered to read his post carefully it is obvious he is speaking of power.

And where do you get "6-10dB" when the 'tech' you posted says 10db? That is the same figure I posted above.