Sound Tech Question....

[Blackout]

So my town has the following sound limits. These seem awful low for an agricultural zoned area! Or will the results be different to the conventional way of measuring sound using weighted measures?

At 0-75 cycles per second a max of 69 db.

At 75-150 cycles per second a max of 60 db.

At 150-300 cycles per second a max of 56 db.

At 300-600 cycles per second a max of 51 db.

At 600-1200 cycles per second a max of 42 db.

At 1200-2400 cycles per second a max of 40 db.

At 2400-4800 cycles per second a max of 38 db.

At 4800-10000 cycles per second a max of 35 db.

 

[JimZaremski]

that doesn't seem to follow any of the traditionally used weighting curves (A or C) unless those are already the weighted levels. They do seem really low, but I can't really pass judgment unless I know how they expect these levels to be measured.

higher frequency sounds are more annoying, but it's not a linear curve (look up Fletcher-Munson or equal loudness contours.) Various industries are moving towards using the Sone ( http://en.wikipedia.org/wiki/Sone ) as a way to measure loudness as it attempts to quantify annoyance better than a simple weighted overall sound pressure level.

 

[Mark Bullard]

Someone in the town has there numbers wrong. But at those numbers there is no way anyone can drive anything down the road or street.

 

[Norm Doerr]

Something is wrong with those numbers.

 

[JimZaremski]

Someone in the town has there numbers wrong. But at those numbers there is no way anyone can drive anything down the road or street.

that's what gets me. I work in a quiet lab, and after reading the OP I took some crude measurements. Something as mundane as a couple of people having a conversation would have run afoul of the limits posted by Blackout.

 

[Norm Doerr]

A refrigerator would violate those numbers

 

[Blackout]

Well, I have more work to do then. I can see it now, me walking in and telling the code officer his numbers are wrong. That will go over well.....

 

[Norm Doerr]

Well, I have more work to do then. I can see it now, me walking in and telling the code officer his numbers are wrong. That will go over well.....

Being I am one of those folks that produces a lot of LOUD noise, I am bit familiar with various DB rules municipal folks usually invoke. Most establish a level, (which is never measured). Most of the time around 100db, AND this level has to be sustained for a certain amount of time duration. My local neighborhood is 100db, sustained for 10 minutes after 10PM to 8AM This includes dogs barking, music devices, loud hot rods power washers, wood chippers etc etc. That thing I see here is not practical by any means.

 

[Kez]

Assume our glow engines run 30,000 RPM, the sound would be 500Hz.and the dB limit is 51. This seems low but what's missing is the distance from the source where the measurement is taken. I think a 40 size boat with a muffler can meet this requirement from 100'.

 

[Blackout]

Assume our glow engines run 30,000 RPM, the sound would be 500Hz.and the dB limit is 51. This seems low but what's missing is the distance from the source where the measurement is taken. I think a 40 size boat with a muffler can meet this requirement from 100'.

It's measured from the property line of the neighbor. This one neighbor has a corner that is 75 feet from the pond. Just a corner, but that's the closest spot and they would likely measure from there. The next neighbor is 500 feet, then 650 feet, and the rest over 1,000 feet.

An 88 db gas boat drops to 55 db about 500 feet away with no sound buffering in the middle. This was from actual testing.

 

[JimZaremski]

Assume our glow engines run 30,000 RPM, the sound would be 500Hz.and the dB limit is 51. This seems low but what's missing is the distance from the source where the measurement is taken. I think a 40 size boat with a muffler can meet this requirement from 100'.

the fundamental will be 500 Hz but engines don't produce pure tones; there is also going to be a ton of energy in the harmonics (1000, 1500, 2000, etc.) which are even higher on the "annoyance meter."

 

[Thomas Hulbert]

Also the wind direction can make a difference at the time of reading.

Meter height can also be a factor as well as obstructions ( buildings, trees etc )