Sound Measurement at MOWOG 3

[MNbiker]

A MAC member has offered to set up a sound measurement station, following SCCA guidelines, at MOWOG 3 this Sunday. We'll be recording sound level readings for all cars in the first two heats, thus providing a minimum of 3 readings for each car at the event. The sound measurements are for informational purposes only, and will be posted on the side of the truck at the conclusion of the 1st and 2nd heats.

-Steve

[MechE30]

Awesome! I'm hoping for more than 70 dB! haha

[seannabend]

what are the scca guidelines on sound?

I've never "heard" of this before

[Chippy569]

I would be "that" member... and this idea sprung out of this thread (http://www.mnautox.com/forums/showthread.php?t=11987). Note that this will also open up 3 more work positions between the first two heats -- 1 person to work with me in my work heat and 2 people to work the heat I don't run in. Look for sign-ups for your work station @ registration!


Regarding the rules, here they are:


APPENDIX I - SOUND MEASUREMENT PROCEDURES
The provisions of this section are recommended, but not presently required. The specific DB levels (values of “XX”) are expected to be assigned by Regions according to the needs of their sites. The competitor shall carry sole responsibility for ensuring their vehicle complies with these Sound Control Standards and Procedures. Vehicle sound emission is not a constant factor that can be trimmed to barely legal (in the manner of engine displacement or vehicle weight.) Sound emissions may vary significantly from morning to afternoon, and day to day, so the competitor is advised to target any vehicle sound emission level “adjustments” to well under the limit, to allow for variations in conditions. The intent of the following rules is to truly make our events quieter by limiting the sound level produced by individual vehicles. Competitors are expected to use mufflers as the primary method for sound reduction. Sound measuring stations will be on both sides of vehicles to ensure sound output levels are below limits.

STANDARD
Maximum limit of (XX) dB, A weighted, at the measuring point.


MEASUREMENT
The measuring point will be established during course set up, and
approved by the event chair. The course map shall be provided to the
chief of sound two days before the event. When possible, measurements will be taken at all event sites to provide information for competitors.
Measurement will be taken at a point on course where the car can
reasonably be expected to be at full throttle, under load, and at high RPM.
The measuring point will be 50 ft from the edge of the course lane, using
a coned gate as a reference. More than one measuring point may be
established.


SOUND STATION(S)
A Sound Station will be established at the measuring point(s) on the course.- At a minimum, an ANSI Type 2 sound with a digital readout will be used. The meter will be mounted on a tripod, 3-4 feet above ground level. The meter will be positioned perpendicular to the vehicle’s direction of travel. The meter will be set to “A” weighting, “Slow” Response. When possible and practical, the Sound Station(s) will be as far away as practical from inhabited buildings. The Sound Station Operator will record the Heat #, Run #, Car # and Class and Sound Reading, on a Log developed for that purpose. Sound Logs will be posted on site after each run group, and on the web following the event. Sound Logs will be maintained for one year. Every car will be measured on every run. The Sound Station Operator and the Grid Sound Control worker will be equipped with a radio on the same channel as the Corners, Grid and Control. One or more (as required) of the “downstream” corner stations will be equipped with a black flag and dedicated flagger. The Sound Control Grid worker will be equipped with a clip board & notepad to record the car number of violators announced by the sound operator, for his reference when the car returns to Grid.


VIOLATIONS
When a vehicle exceeds (XX – 3) dBA, the sound operator will inform the
grid sound control worker. When a vehicle exceeds (XX + 3) dBA, the sound operator will announce over the radio, “sound flag, sound flag,” then state the car number and class, and the measured reading. The Grid Sound Control Worker will record the car number and sound reading. The corner station(s) with the black flag will display it when called by Sound Control, so it can be seen by the driver, signifying to the driver that his vehicle has exceeded the (XX + 3) dBA secondary limit. The driver must immediately come off the throttle and continue through the course, without either stopping or driving at a competition pace. Any run (XX) dBA or over will be scored a DNF. The driver will be notified of any measurement over (XX – 3) dBA. When a car in violation ((XX) dBA or over) returns to grid, the Grid Sound Control worker will notify the driver of the car’s measured sound level. The driver will be given the opportunity for a “mechanical delay” to attempt to reduce the vehicle’s sound level. If, in the judgment of the Grid Sound Control worker, the driver has attempted a viable remedy, he will authorize a “second chance run”. If the driver(s) declines any “repair” action, or the “repair” is deemed inadequate or inappropriate by the Grid Sound Control Worker, the driver(s) will forfeit all subsequent runs in that vehicle. The Grid Sound Control Worker may
offer advice to competitors. This advice, however, shall be in no manner
be construed to imply that said suggested corrective action(s) absolves
the competitor from complying. If the vehicle exceeds either limit on the
“second” chance run, the vehicle may be given one “final chance” run if
the vehicle meets all the requirements of the previous paragraph (second
chance run). If the vehicle exceeds the limit on the “final” chance run, all subsequent runs by that vehicle, if any, are forfeited. Drivers may appeal the decision of the Grid Sound Control Worker to the Event Chair.


---



Now, a lot of that will not apply as we are not doing violations or anything like that. This is mostly an informational test so that volume-curious members can get a reasonable measurement of their sound output.


This is the time where I feel I should bring up the importance of volume exposure and your hearing. I believe the most often restriction level for these SCCA events (the "xx" in the rules) is 90dB. However, keep in mind that this measurement is taken from 50' away. Because sound eminates spherically away from the source, and because decibels are a logarithmic scale, the end result is that for every doubling of distance away from the source the level decreases by 3dB. So the level that I record from 50' away is roughly 19dB quieter than from 1' away. I bring this up because of what you will read below regarding constant tone exposure.



Decibel Exposure Time Guidelines

Accepted standards for recommended permissible exposure time for continuous time weighted average noise, according to NIOSH and CDC, 2002. For every 3 dBs over 85dB, the permissible exposure time before possible damage can occur is cut in half.

Continuous dB Permissible Exposure Time
85 db: 8 hours
88 dB: 4 hours
91 db: 2 hours
94 db: 1 hour
97 db: 30 minutes
100 db: 15 minutes
103 db: 7.5 minutes
106 dB: 3.75 min (< 4min)
109 dB: 1.875 min (< 2min)
112 dB: .9375 min (~1 min)
115 dB: .46875 min (~30 sec)



So if I get a reading of 90dB from 50' away, first off you have a damn loud car, and second off where you're sitting in the driver's seat you're experiencing roughly 109dB. I realize that it is not a "constant tone" and that unless you're doing a very long course it won't take you 2 minutes, but I'm just saying that exposure to that loud of a source will eventually result in permanant hearing loss at the loudest frequency, so if you have a "loud" car do think of your ears. After all, if you can't hear, you can't enjoy what I aim to do for a living!

[MNbiker]

... I believe the most often restriction level for these SCCA events (the "xx" in the rules) is 90dB.
Nope, the SCCA guidelines aren't nearly that strict. Here are the guidelines for the 2009 Solo Nationals, as published in the April 2009 Fastrack News:


Per the SEB, the requirements of Appendix I (Sound Control) will be applied at the 2009 Nationals. The specified dB level will be 103 dBA.


It's also worth noting that several SCCA Solo National Tour events have used a limit of 95 dBA measured at 75'.

-Steve

[Chippy569]

really? wow, that's really freaking loud! 103dB at 50' is 122dB at 1' which is permanant hearing loss in 7.5sec....

[seannabend]

After all, if you can't hear, you can't enjoy what I aim to do for a living!

I aggree with you that hearing is very important and so many people take it for granted.
I just had no idea that the SCCA actually penalized people for having loud cars.

I read a very good article in Cycle World last year that talked about hearing loss due to wind noise when riding motorcycles even with a full helmet.

it will be interesting to see what kind of sound levels our cars put out

[MNbiker]

I just had no idea that the SCCA actually penalized people for having loud cars.
It's standard practice at Club Racing events. It's still rare at Solo events, but becoming more common.

[G. Jay]

really? wow, that's really freaking loud! 103dB at 50' is 122dB at 1' which is permanant hearing loss in 7.5sec....

Distance from the source to the driver, body structure, a helmet and hopefully ear plugs mean the driver shouldn't experience anything nearly that loud. Just don't put your tailpipe a foot away from your ear and vis versa.

[phile]

Distance from the source to the driver, body structure, a helmet and hopefully ear plugs mean the driver shouldn't experience anything nearly that loud. Just don't put your tailpipe a foot away from your ear and vis versa.

I'm sure my tailpipe is at least 2 feet from my ear.

[Bear]

I'm sure my tailpipe is at least 2 feet from my ear.


YOUR tailpipe... or your car's tailpipe? :D

[zaisaroni]

YOUR tailpipe... or your car's tailpipe? :D
:lol:

Well played!

[Chippy569]

Distance from the source to the driver, body structure, a helmet and hopefully ear plugs mean the driver shouldn't experience anything nearly that loud. Just don't put your tailpipe a foot away from your ear and vis versa.

This is very true. I'm just saying, be careful out there especially if your car is approaching those kinds of volumes. If your ears are "ringing" (ie tinnitus (http://en.wikipedia.org/wiki/Tinnitus) is setting in) it's already too late.

[phile]

YOUR tailpipe... or your car's tailpipe? :D

My Seven's tail pipe, which is really a side pipe on the driver side.

[Chippy569]

aww phil, you went and took a good joke all literally.

[phile]

aww phil, you went and took a good joke all literally.

The joke still stands. Real info didn't kill the joke.

[Chippy569]

Results have been posted in the general section (http://www.mnautox.com/forums/showthread.php?p=140617), so feel free to check it out!