2012 Sound Level Suggestion

[Whis]

Oh heck no.

I disagree.

Reasons:
1. Sound waves attenuate fast. A big single makes really heavy pulses that are readily seen at 19.w/e inches away. At 50 feet though?

2. Why can't we have a rule like most racing series where you have to be 90-95 dB at 100 ft away?

3. I think not making sound shouldn't mean you don't pass tech. I think it should mean that you loose points for not making it. Being over by .75 dB and not making sound is pretty annoying. Make the hard cap like 120.

Whis

ISU Engine Team Lead

[Whis]

Oh heck no.

I disagree.

Reasons:
1. Sound waves attenuate fast. A big single makes really heavy pulses that are readily seen at 19.w/e inches away. At 50 feet though?

2. Why can't we have a rule like most racing series where you have to be 90-95 dB at 100 ft away?

3. I think not making sound shouldn't mean you don't pass tech. I think it should mean that you loose points for not making it. Being over by .75 dB and not making sound is pretty annoying. Make the hard cap like 120.

Whis

ISU Engine Team Lead

[Luniz]

I think some sort of dynamic sound level monitoring should be introduced, becuase the static method has some difficulties and inaccuracies.

For example: The (subjectively) loudest car our team has ever produced has been measured with 107db in Hockenheim. Our subjectively most silent car was over 110db due to an unfavorable position of the exhaust outlet.
And everyone knows that singles are far more noisy when under load i/e accelerating.

My suggestion would be to try and make up some sort of data aquisition at the next comp in an acceleration zone of the autoX-track, at a fixed distance to the track and a specified sound meter position. Just in order to get some ballpark info at what levels to expect. And then take these levels and make up a rule from that.

[RANeff]

Honestly I think a static sound test is worthless anyways. It should be run like SCCA Sound reg's, under load at a distance. Were at a racetrack mor most FSAE Events, and and impact due to sound is much more than 50 feet away.

[Pennyman]

Just a little anecdote,

At Laguna Seca, the sound meter is on the outside of the exit of turn 5, right as you start to go up the hill. This is the area where the cars are probably under the most load.

The booth is 100ft from the track, and the normal noise reg is 95db. A stock Z06 Corvette has to lift there to not fail the reg. They only have 5 unlimited noise weekends per year.

So teams simply route the exhaust to the other side to "quiet" their exhaust.

This might work in FSAE, but being that a loophole would simply be to rotate your exhaust tip away from the meter, I don't know.

just my 1c

[Michael Royce]

Be careful what you wish for! A little history should put things into perspective and explain why things are the way they are.

Up to about 10 years ago, the noise test at Formula SAE WAS a dynamic, pass-by test, such as you are all describing. It had two problems. Firstly, it was not a controlled and repeatable test, and secondly as such, cars would pass the initial noise test and then fail the monitoring that was done during the dynamic events and were then disqualified. The result was some very, very unhappy teams!!

Then at the second or third Formula Student event in the UK, the MSA scrutineer assigned to the event did a comparison of the then current FSAE test and MSA’s static, ½ metre test. The correlation was pretty good. So about 10 years ago, the Rules Committee changed the noise test to the current static, no load, 45 degrees, ½ metre test. As a long stroke engine typically runs at a lower speed than a short stroke engine, the test speed is based on the stroke of the engine. The test speeds were chosen to represent approximately 75% of the normal maximum average piston speed of a typical gasoline engine, namely 3,000 ft/minute.

The test is easy to run, and within normal noise test practices, is repeatable. It is used by several motor sports sanctioning bodies including the MSA in the UK and FIM for the Moto GP bikes. In fact I used it the on the bikes at Indianapolis just over a week ago.

With such an easy test, I am continually surprised that teams turn up at an event and struggle to pass the noise test. It appears that many have never run a noise test on their car!

Unfortunately, the noise from a given vehicle does change with atmospheric conditions. However, unlike engine output that has correction factors such as are given in SAE Practice J1349, there are no recognized correction factors for noise. So the number you get is the number that is used. Because of this variability, I have always recommended to teams that they aim for 3-4 dBA below the required limit. And yet teams continue to try and get as close to the 110 dBA limit as possible.

Therefore, my suggestions to teams are:
1. Borrow a sound level meter from one of the university departments. Some one has to have one, even if it is the department that has responsibility for checking for compliance to the OSHA requirements. If you cannot borrow one, you can get one from Radio Shack (admittedly not a Type 1) for under $100.
2. Get the meter calibration checked.
3. Run a noise test on your current car BEFORE you set out for the event.
4. Aim to be 3-4 dBA below the required limit. Don’t try and shave the margin in the hope that it will improve your engine output. It is unlikely to do so and not worth the effort, especially if you fail noise at the event and have to scramble!

Now, the Rules Committee has been aware for several years that volunteers have complained that the single cylinder cars are painful to the ears even after passing the noise test. The complaints have come from a number of areas including the skid pad and the endurance event. However, as yet, the Committee has not figured out an equitable way of solving the problem.

[Mike Cook]

Thanks for the history, Mr. Royce. People always want to reinvent everything. A pretty frequent problem with FSAE in general, I think.

And lets not lie, it is not difficult to pass sound tech. However I think most people don't want to add an additional 5lb to the car if they don't have to.

What I have found out, is that is probably a good idea to have a 'loud' setup and a 'quiet' setup. We have found that if we run a 'quiet' setup around our university we bother a lot less people and the police visit us a lot less. This is just a no brainer if you want to continue good relations with the university and want to continue driving on their property. However, most SCCA events we run and even at FSAE, we run the 'loud' setup. However, if it doesn't pass than we always have a quieter muffler we can put on.

I like the test as is because it seems fairly repeatable and easy to replicate at home. If you try to do track noise testing, there are a lot more variables (like other noise sources, postioning of your exhaust, atmospheric conditions). I think dropping the limit to 107dBA, is probably a good idea because we can start running a quieter setup everywhere. I can tell you that after a day of testing my ears are not in good shape (should probably run ear plugs in my helmet).

Mike

[Whis]

Thanks for the history, Mr. Royce.

I agree with Mike Cook, although...

Why is there a hard cap? Why not soft?

Also, I think my main problem is that calibration and meter weighting seem to be an issue. We seemed to have some problems with the sound testing at competition this year due to meter settings being... off. This is a rather subjective view, since I can't back it up with numbers, but a number of teams that passed at another competition didn't seem to pass at the one I was at.

Quiet sure is nice though, for all of the reasons listed above.

[RobbyObby]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Whis:
Thanks for the history, Mr. Royce.

I agree with Mike Cook, although...

Why is there a hard cap? Why not soft?

Also, I think my main problem is that calibration and meter weighting seem to be an issue. We seemed to have some problems with the sound testing at competition this year due to meter settings being... off. This is a rather subjective view, since I can't back it up with numbers, but a number of teams that passed at another competition didn't seem to pass at the one I was at.

Quiet sure is nice though, for all of the reasons listed above. </div></BLOCKQUOTE>

That's something I've always wondered as well. At West last year the actual test meter's batteries died so until they could charge the batteries they ended up using 2 team supplied meters and averaging the two numbers since they weren't calibrated. If I'm not mistaken some of the numbers were up to 5 dBA off giving an error of +/- 2.5 dBA. All the while they were scrutineering down to the tenth of a decibal. Tell me how that makes any sense!

[TMichaels]

A man who has one watch always knows exactly what the time is. A man with two watches is never sure....
@RobbyObby:
As Michael said, just aim to be 3 to 4 dBa below and you will also be able to pass if your test meter or the test meter at comp is 2.5dBa off.

I also agree that a pass-by-test is not really practical because of the mentioned reasons.
There would be a lot of discussions or protests by the teams regarding the test procedure and there is no way to standardize this in all competitions, because of the different venues. Right now we have a well defined test which every team can repeat before comp.
Just build an electric car and your get rid of the noise test http://fsae.com/groupee_common/emoticons/icon_smile.gif

Regards,

Tobias

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RobbyObby:
That's something I've always wondered as well. At West last year the actual test meter's batteries died so until they could charge the batteries they ended up using 2 team supplied meters and averaging the two numbers since they weren't calibrated. If I'm not mistaken some of the numbers were up to 5 dBA off giving an error of +/- 2.5 dBA. All the while they were scrutineering down to the tenth of a decibal. Tell me how that makes any sense! </div></BLOCKQUOTE>

I personally witnessed a 7 dB difference between meters at that event, which IMO is wayyyy beyond acceptable. Many teams that passed noise in MI a month before failed. Although from what I gather operator error played a large role in this, and once they figured out what position the switches were supposed to be on people started passing, go figure. Not to mention Michigan State had to supply their own two sound meters for the event.

[Adambomb]

To clarify: the 7 dB difference was between the event-sponsored meter (before it died) to the average of the MI State meters. Couple that with the rest of the info, and something stinks. Although I wouldn't say it's the way the rules are written.

[DcooL]

The sound event judges at California this year were unfamiliar with the meter and its controls to get it in A-weighted mode. I had to personally ask for them to make the change and we had no problems passing the test. However, I feel sorry for the teams that were subjected to raw SPL measurements before us.

As for the single-cylinder engines clearing the noise test yet being painfully loud, I have experienced this first hand, and can attribute that to the section of the rules that specifies 'fast weighting' to be applied. Because its desired to measure transients, 'fast weighting' is an industry standard way of utilising a time based moving point average. As a result, a single with FEWER exhaust pulses at the same RPM as a 4-cyl. can afford to be louder i.e. Higher SPL/pulse (this is painful to the ears), but the time averaged smoothing in the meter lets it go.

I don't believe there is a way around that. Just another thing peculiar to the single.

[Æssahættr]

I thought the the fast time weighting is more catered to capturing rapid changes in peak level rather than correcting for them? Also, as the 'instantaneous' peak level is desired in this case, how much time weighting is allowed on the statistic?

I suspect the A weighting is the big benefit to the singles due to the large filter attenuation in the low-mid frequency range.

[DcooL]

Yes, the fast weighting does capture the peaks, but in the form of a moving point average. The window for the instantaneous snapshot can be adjusted on most meters, especially the gizmomatic B&K used at comp. My concern is about illiteracy on the part of the event staff in using it correctly. As for the actual time weighting, based on what I have seen, I doubt anyone knows what settings get used.

The A- weighting helps the singles by weighting the lows by a factor less than 1 and also because a single with a decent exhaust-muffler config will have practically non-existent high frequency output.

Edit:
On a side note, in general, rules allow cars to have a higher rev-limit than at the noise test, and I am sure SOME teams make use of this, and hence their car can sound louder on the track than at the test.

[RenM]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DcooL:
On a side note, in general, rules allow cars to have a higher rev-limit than at the noise test, and I am sure SOME teams make use of this, and hence their car can sound louder on the track than at the test. </div></BLOCKQUOTE>

I guess the opposite is a problem for the 4s. Most 4 cylinder Teams wont rev as high as the stock engine because of the restrictor. thus the noise test rpm is very close to the end of the rev range.

[DcooL]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> I guess the opposite is a problem for the 4s. Most 4 cylinder Teams wont rev as high as the stock engine because of the restrictor. thus the noise test rpm is very close to the end of the rev range. </div></BLOCKQUOTE>

MOST won't, but if you looked hard enough, you'd find some...

[2BWise]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pennyman:
Just a little anecdote,

At Laguna Seca, the sound meter is on the outside of the exit of turn 5, right as you start to go up the hill. This is the area where the cars are probably under the most load.

The booth is 100ft from the track, and the normal noise reg is 95db. A stock Z06 Corvette has to lift there to not fail the reg. They only have 5 unlimited noise weekends per year.

So teams simply route the exhaust to the other side to "quiet" their exhaust.

This might work in FSAE, but being that a loophole would simply be to rotate your exhaust tip away from the meter, I don't know.

just my 1c </div></BLOCKQUOTE>

This may work at Laguna, but doesn't at my local track and nor would it at say, MIS. The issue is that you cross the meter again in the opposite direction, so now your attempt to aim the exhaust away from the meter now points it directly at it.

There have been cars at my local track that pass in one direction, but at another point on the track, further away from the meter, will then fail. A directional tip would have to be adjustable to counter this at MIS where the course is setup as a down-and-back.

[Drew Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DcooL:

Edit:
On a side note, in general, rules allow cars to have a higher rev-limit than at the noise test, and I am sure SOME teams make use of this, and hence their car can sound louder on the track than at the test. </div></BLOCKQUOTE>



Now you're thinking like a racer, keep on this train of thought and your whole world will open up.....


.....what else would change the sound output under no load?

[Wesley]

Both musicians and racers should always carry the right tune, and must have proper timing.

[Hector]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">My concern is about illiteracy on the part of the event staff in using it correctly. </div></BLOCKQUOTE>Have a problem? Volunteer as a course worker. Most of the comp is run by volunteers offering their time for free, and are not necessarily experts. If you ever think you're being wronged, talk to them (much like you did). They're almost always more than willing to listen.

[RenM]

my opinion is, that they only want to introduce it to make those supercharged 1 cylinder cars a little bit more quiet and have not found an easier or more intelligent way to do it.
I dont buy any of this "support the industries efforts to produce greener cars", because this has nothing to do with how "green" a car is.

[RANeff]

RenM,

Have you ever heard of noise pollution? It is part of the Green Movement....

[Nick Renold]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DcooL:

Edit:
On a side note, in general, rules allow cars to have a higher rev-limit than at the noise test, and I am sure SOME teams make use of this, and hence their car can sound louder on the track than at the test. </div></BLOCKQUOTE>



Now you're thinking like a racer, keep on this train of thought and your whole world will open up.....


.....what else would change the sound output under no load? </div></BLOCKQUOTE>


B1.2.2 Once the vehicle is approved to compete in the dynamic events, the ONLY modifications permitted to
the vehicle are those listed below. They are also referenced in Part C of the Formula SAE Rules –
Static Event Regulations.
e. Adjustment to engine operating parameters, e.g. fuel mixture and ignition timing


De-tune the engine for exhaust event?

[RenM]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by RanE5-CSU:
RenM,

Have you ever heard of noise pollution? It is part of the Green Movement.... </div></BLOCKQUOTE>

The FSAE events are on a race track. The cars there are usually much louder then ours. There is no need for the environment of a race track to have FSAE cars that are generally less noisy.

[Wesley]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Nick Renold:
De-tune the engine for exhaust event? </div></BLOCKQUOTE>

Doesn't take long to set yourself up a map for sound - though you're still subject to retest if you're found to be too loud with a new map.

Really, there are specific points in the fuel map that are consistently used for noise testing... playing with fuel and spark in those can get you a 1-2db change if you're on the edge.

You still have to have a sufficient muffler/header design though...

[BrandenC]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wesley:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Nick Renold:
De-tune the engine for exhaust event? </div></BLOCKQUOTE>

Doesn't take long to set yourself up a map for sound - though you're still subject to retest if you're found to be too loud with a new map.

Really, there are specific points in the fuel map that are consistently used for noise testing... playing with fuel and spark in those can get you a 1-2db change if you're on the edge.

You still have to have a sufficient muffler/header design though... </div></BLOCKQUOTE>

Seems like this train of thought is specifically barred by the rules:

B1.2.3 The vehicle must maintain all required specifications, e.g. ride height, suspension travel, braking
capacity, sound level and wing location throughout the competition.

[moose]

Originally posted by moose:
I personally read that rule that says you can't just pass sound, you need to always be able to pass (e.g. if you're super loud - you can be asked to run it again, if you fail then you lose the sticker until it's fixed). But at the same time, if a car breaks the sound limit at 5K RPM, it still won't pass the test. However, if a car is louder at 10K and full throttle, that won't ever actually get tested.

[Wesley]

That's why I qualified my first statement with "you're still subject to retest if you're found to be too loud with a new map."

However, if you just change the fuel table points your engine operates at during the noise test, you'll pass the retest too, since you're meeting the rule.

Also, if you're noticeably louder than you should be, fuel and spark tuning isn't going to help you. The advice is for teams on the edge of 110dBA