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LRSLA · 09-21-2004, 07:12 PM

Sorry for the delay in posting I have been out of town.

I have to agree with you on the overall quality of the posts on this forum.
This has been a good forum for communication.

You are correct on the operational test being 90db in maine.
I must have had a middle age moment. :-))

The rule of thumb in noise measurement is that doubling the distance from a source decreases the noise level by 6db; Halving the distance increases it by 6db.

So if the operational limit is 75db at fifty feet, and I take a measurement from shore from 1/2 mile away and the SPL (sound pressure level) is 72db. I can assume that at 1/4 mile the measurement would be 6db higher, or 78db. At 1/8 of a mile the SPL should be about 84db. At 1/16 of a mile the SPL should be 90db.

This measurement was forwarded to the Warden service and they caught up with the boat later in the day. The Warden's preformed a Stationary test and the boat failed that test. Later in the summer the boat was cited again and told to tie up until the boat was brought into compliance.

I really need to add that when ever I take measurements or forward info on measurements I add distance to my distance from source measurement.
If I take a measurement at 150 feet I forward that the measurement was taken at 200 feet. I try to build in a conservative approach to sound measurement. LRSLA has begun using laser ranging scope to obtain distance readings.

I have found that most of the boats I have measured are so far over the operational limit that obtaining good quality measurements is not a problem. This why I have pressed the issues with the State. I have found that obtaining operational tests in real world environments is not difficult.

The Maine State operational noise test procedure is supposed to be preformed at fifty feet from the source. All of my measurements were taken at least 200>300 from the source.

I also take wind, temperature and barometric readings prior to take measurements.
I also re-calibrate my meter at the beginning of each test day.

Mee'n'Mac, post was excellent and a very concise explanation of sound measurement. The only issue I would bring up is that noise measurement has not really moved out of the factory and lab and into the real world. Many communities are using the C scale because it more closely represents the impact that audible low frequency sound has on communities.

Additionally my feeling is that a real world impact should be
mitigated by a real world test. In essence, surface water reflection of sound and other impacts on the noise measurement process are OK if they support normal measurement of the normal sound scape on the lake and the noise impact of the boat of issue.

I have witnessed reduction in noise level by trees but never increase in sound levels.

I would speculate that this is due to the extreme amplitude of the
offending craft. One key point is that a source must be at least 10 db over the background noise level in order to measured effectively an legally.

Of course environmental conditions effect the efficiency of a sound wave moving through air and thus can affect it's impact.
Yet once again, this is a real world condition, and if a boat is operating during a time when those atmospheric conditions are present, then the boat should be considered illegal if it fails a test at that time.

Most of my sound traces were taken at around two to three hundred feet from the source boat. All the traces were over 75db even at that distance. Most traces were around 86>89db at two to three hundred feet.

You are correct that you can have a source with a very high db, but almost not be able to hear it. SPM's, (Sound Pressure Meters) are calibrated with a
certified calibrator. A testing officer should calibrate the meter before and after each test. Meter readings can change with changes in temperature and barometric levels. SPM's must be calibrated and the calibrators must be calibrated each year by a certified sound engineer. The certifications are kept with the units to prove this calibration.

The calibrator emits a very precise tone at a specific frequency and a specific SPL. My meter calibrates at 114db. The microphone on the meter is placed very close to the calibrators speaker for calibration and then the meter is adjusted to that level of sound. If you hold the calibrator at arms length you can not hear it. Yet, the sound level adjacent to the speaker is 114db.

As for mandatory education I would support this , absolutely!!!

The reality is that bloody hell would break out in Maine if this were attempted to be floated. LRSLA is planing to bring up the issue when it meets with State Reps this winter. We are not hopeful that the issue will move forward. IFW and the Federal government would love to have a mandatory boater education course in place in Maine. In Maine many of the 6000 bodies of water are not heavily impacted by recreational boating. To ask a fellow who lives in a northern township were he might see ten boats in a summer, to take a boater education course, is a hard sell in Maine.

As far as warning boaters.

We put info in the local press and contacted marina owners to inform them of the enforcement. And as I mentioned this issue has been coming to boil for three seasons. Each season has seen increased enforcement.

I also need to correct one of my statements. The impact of noise is subject on an individual basis. What is not subject is the measurement of sound.
The measurement of sound is extremely objective and scientific.

09-21-2004, 07:12 PM	#78
LRSLA Junior Member Join Date: Sep 2004 Posts: 19 Thanks: 0 Thanked 1 Time in 1 Post	Real world noise enforcement Sorry for the delay in posting I have been out of town. I have to agree with you on the overall quality of the posts on this forum. This has been a good forum for communication. You are correct on the operational test being 90db in maine. I must have had a middle age moment. :-)) The rule of thumb in noise measurement is that doubling the distance from a source decreases the noise level by 6db; Halving the distance increases it by 6db. So if the operational limit is 75db at fifty feet, and I take a measurement from shore from 1/2 mile away and the SPL (sound pressure level) is 72db. I can assume that at 1/4 mile the measurement would be 6db higher, or 78db. At 1/8 of a mile the SPL should be about 84db. At 1/16 of a mile the SPL should be 90db. This measurement was forwarded to the Warden service and they caught up with the boat later in the day. The Warden's preformed a Stationary test and the boat failed that test. Later in the summer the boat was cited again and told to tie up until the boat was brought into compliance. I really need to add that when ever I take measurements or forward info on measurements I add distance to my distance from source measurement. If I take a measurement at 150 feet I forward that the measurement was taken at 200 feet. I try to build in a conservative approach to sound measurement. LRSLA has begun using laser ranging scope to obtain distance readings. I have found that most of the boats I have measured are so far over the operational limit that obtaining good quality measurements is not a problem. This why I have pressed the issues with the State. I have found that obtaining operational tests in real world environments is not difficult. The Maine State operational noise test procedure is supposed to be preformed at fifty feet from the source. All of my measurements were taken at least 200>300 from the source. I also take wind, temperature and barometric readings prior to take measurements. I also re-calibrate my meter at the beginning of each test day. Mee'n'Mac, post was excellent and a very concise explanation of sound measurement. The only issue I would bring up is that noise measurement has not really moved out of the factory and lab and into the real world. Many communities are using the C scale because it more closely represents the impact that audible low frequency sound has on communities. Additionally my feeling is that a real world impact should be mitigated by a real world test. In essence, surface water reflection of sound and other impacts on the noise measurement process are OK if they support normal measurement of the normal sound scape on the lake and the noise impact of the boat of issue. I have witnessed reduction in noise level by trees but never increase in sound levels. I would speculate that this is due to the extreme amplitude of the offending craft. One key point is that a source must be at least 10 db over the background noise level in order to measured effectively an legally. Of course environmental conditions effect the efficiency of a sound wave moving through air and thus can affect it's impact. Yet once again, this is a real world condition, and if a boat is operating during a time when those atmospheric conditions are present, then the boat should be considered illegal if it fails a test at that time. Most of my sound traces were taken at around two to three hundred feet from the source boat. All the traces were over 75db even at that distance. Most traces were around 86>89db at two to three hundred feet. You are correct that you can have a source with a very high db, but almost not be able to hear it. SPM's, (Sound Pressure Meters) are calibrated with a certified calibrator. A testing officer should calibrate the meter before and after each test. Meter readings can change with changes in temperature and barometric levels. SPM's must be calibrated and the calibrators must be calibrated each year by a certified sound engineer. The certifications are kept with the units to prove this calibration. The calibrator emits a very precise tone at a specific frequency and a specific SPL. My meter calibrates at 114db. The microphone on the meter is placed very close to the calibrators speaker for calibration and then the meter is adjusted to that level of sound. If you hold the calibrator at arms length you can not hear it. Yet, the sound level adjacent to the speaker is 114db. As for mandatory education I would support this , absolutely!!! The reality is that bloody hell would break out in Maine if this were attempted to be floated. LRSLA is planing to bring up the issue when it meets with State Reps this winter. We are not hopeful that the issue will move forward. IFW and the Federal government would love to have a mandatory boater education course in place in Maine. In Maine many of the 6000 bodies of water are not heavily impacted by recreational boating. To ask a fellow who lives in a northern township were he might see ten boats in a summer, to take a boater education course, is a hard sell in Maine. As far as warning boaters. We put info in the local press and contacted marina owners to inform them of the enforcement. And as I mentioned this issue has been coming to boil for three seasons. Each season has seen increased enforcement. I also need to correct one of my statements. The impact of noise is subject on an individual basis. What is not subject is the measurement of sound. The measurement of sound is extremely objective and scientific.