Winnipesaukee Forum - View Single Post

ApS · 02-10-2006, 09:28 AM

Since I've survived a career just an elbow-distance to the loudest noises that mankind can produce, I'd like to chime in here. (Skip can back me up on my career choice).

As I've previously posted, I've routinely used a Bruel & Kjaer dB meter in my employment. It was required because the sound needed to be quantified with a number—and not leaving it up to any person's opinion. At the end of the day, there was a "number" produced, but bore scant relationship to what was actually heard.

I've pondered this phenomenon, and can only conclude that sound—particularly over water—is a strange duck.

Why is it that a speedboat's exhaust on the Weirs side of Rattlesnake Island—can be heard while adrift on the Broad's side of Rattlesnake Island? That's nearly three hundred feet of soil, trees, and granite! How can exhaust noise travel through hundreds of acres of forest while still needing to travel through another 70-foot-depth of clay, rocks, forest "duff", and soil—to be heard at my dock over a ½-mile away?

I've consulted with sound engineers—who should know—and came away empty.

My guess is best expressed as this: If you pluck a guitar's steel string in the open air, you get a pleasant sound. If you attach the string to a hollow "sounding board" (like a guitar) it is the same pleasant sound, but amplified.

The noisiest boats on Winnipesaukee can be heard from miles away—even as they pass behind islands—and even when abeam and miles away. Are their hulls acting as a "sounding board" for their exhaust- and exhaust-related noises?

I think so.

The entire "noise" issue needs to be readdressed for lakes surrounded by mountains. IMO, there is a strong liklihood that a dB meter needs to be supplemented with a seismometer in such environments.

As to the new bill's "close" measure:

Everyone can recall the noise that a Harley motorcycle makes at idle in front of your favorite restaurant; however, just as he "gives it the gas", the noise increases dramatically as the "load" on the engine jumps. In the space of just ten feet, the noise can be far more deafening than it was at idle.

Now take New Jersey—please:

I regret last year's New Jersey's action of eliminating the "drive-by" noise-testing of speedboats. They cited it as "too dangerous"—and well they should. Boating speeds ratchet upwards every year. Speedboat manufacturers are tranfering their speedboat basic design and converting them to "Express Cruiser", or some other speedy "Family Boat" experience.

Within the same year, NJ politicos defeated a speed limit initiative at the same time that drive-by noise testing was defeated! New Jersey has started a demanding "Boater Education" program this year, and widely-held complaints can be read on Internet boating sites.

BTW: Maryland has a proposal for 100% PFD use on any moving boat this year.

(Seems to me that mandatory PFDs may have actually contributed to a 70-MPH double-fatality on Michigan waters last summer).

02-10-2006, 09:28 AM	#29
ApS Senior Member Join Date: Jan 2005 Location: Florida (Sebring & Keys), Wolfeboro Posts: 6,052 Thanks: 2,282 Thanked 789 Times in 565 Posts	Please Pass the Bruel & Kjaer over here. Since I've survived a career just an elbow-distance to the loudest noises that mankind can produce, I'd like to chime in here. (Skip can back me up on my career choice). As I've previously posted, I've routinely used a Bruel & Kjaer dB meter in my employment. It was required because the sound needed to be quantified with a number—and not leaving it up to any person's opinion. At the end of the day, there was a "number" produced, but bore scant relationship to what was actually heard. I've pondered this phenomenon, and can only conclude that sound—particularly over water—is a strange duck. Why is it that a speedboat's exhaust on the Weirs side of Rattlesnake Island—can be heard while adrift on the Broad's side of Rattlesnake Island? That's nearly three hundred feet of soil, trees, and granite! How can exhaust noise travel through hundreds of acres of forest while still needing to travel through another 70-foot-depth of clay, rocks, forest "duff", and soil—to be heard at my dock over a ½-mile away? I've consulted with sound engineers—who should know—and came away empty. My guess is best expressed as this: If you pluck a guitar's steel string in the open air, you get a pleasant sound. If you attach the string to a hollow "sounding board" (like a guitar) it is the same pleasant sound, but amplified. The noisiest boats on Winnipesaukee can be heard from miles away—even as they pass behind islands—and even when abeam and miles away. Are their hulls acting as a "sounding board" for their exhaust- and exhaust-related noises? I think so. The entire "noise" issue needs to be readdressed for lakes surrounded by mountains. IMO, there is a strong liklihood that a dB meter needs to be supplemented with a seismometer in such environments. As to the new bill's "close" measure: Everyone can recall the noise that a Harley motorcycle makes at idle in front of your favorite restaurant; however, just as he "gives it the gas", the noise increases dramatically as the "load" on the engine jumps. In the space of just ten feet, the noise can be far more deafening than it was at idle. Now take New Jersey—please: I regret last year's New Jersey's action of eliminating the "drive-by" noise-testing of speedboats. They cited it as "too dangerous"—and well they should. Boating speeds ratchet upwards every year. Speedboat manufacturers are tranfering their speedboat basic design and converting them to "Express Cruiser", or some other speedy "Family Boat" experience. Within the same year, NJ politicos defeated a speed limit initiative at the same time that drive-by noise testing was defeated! New Jersey has started a demanding "Boater Education" program this year, and widely-held complaints can be read on Internet boating sites. BTW: Maryland has a proposal for 100% PFD use on any moving boat this year. (Seems to me that mandatory PFDs may have actually contributed to a 70-MPH double-fatality on Michigan waters last summer).