5 ms·

Noise power and perceived volume are nonlinear. When the article says: These simple ridges have reduced noise levels by more than half. they are speaking of pow

by jws 8y ago

Noise power and perceived volume are nonlinear. When the article says: These simple ridges have reduced noise levels by more than half. they are speaking of power. This means a reduction in perceived noise of about 1/6th. It is about the minimum change at which a person says "Oh yeah, that's quieter." Later in the article they mention including more measures from the airlines' planes and operating procedures to achieve a total of a 10db reduction, which gets rid of 90% of the energy and people will say "Oh yeah, that's about half as loud."

sandworm101 8y ago
I work with aircraft (big helicopters) and field noise complaints. I find time of day and weather mean far more than actual noise energy. 7pm, sunset, calm wind, sunday = noise complaint. We never get complaints at 11am on a windy or rainy tuesday. I am very polite on the phone, but if you choose to retire beside an AIRBASE! Our helicopters have been flying over your house decades before it was ever a house. Sue your real estate agent for not telling you exactly why zoning limits your neighbourhood to two-story non-commercial structures.
- Washuu 8y ago
  Weather does have an affect on noise along with the differential between air temperature near the ground and higher up. It is common for the local government testing facility to send out notices to expect louder than normal booms from rocket testing during different weather.
  - sandworm101 8y ago
    I dont think it is physics. People are eating dinner outside in good weather. There is also a group dynamic. Some people call on speakerphone and it is obvious they are just showing thier dinner guests that they know my phone extension. That senario, the likelihood that people are eating dinner as a group outside, is the best means of prediction. We alter our operations as best we can accordingly. There is a common joke in air forces, at least western air forces: Plane to loud? Did you see a red star on it? You're welcome.
    - DonHopkins 8y ago
      My President's too loud, and I think there's a red star on him.
    - Washuu 8y ago
      Some sources that can explain it better that I can: https://physics.stackexchange.com/questions/255844/do-clouds-reflect-ambient-noise https://physics.stackexchange.com/questions/255844/do-clouds... https://physics.stackexchange.com/questions/133198/why-do-i-always-hear-remote-train-horn-at-night/133207#133207 https://physics.stackexchange.com/questions/133198/why-do-i-...
- michaelbuckbee 8y ago
  I live in the Hampton Roads area and realtors are very up front about jet noise and crash danger. There are maps of high and low noise areas, you are asked to sign a waiver stating that you are aware your home is in a high noise area, etc.
- sandworm101 8y ago
  The difficulty is that helo operations are pushed around by the bigger/faster stuff. So it might be years before a combination of wind, weather and traffic cause us to approach/depart over a particular neighborhood. In an emergency, a SAR callout, we will fly over areas that might never have seen a flyover before.
- dingaling 8y ago
  > but if you choose to retire beside an AIRBASE! The problem with that position, at least in the UK, is that the social contract between the airport operator and the local residents was never revisited. Most of the UK's airports and airbases date from the 1920s and 30s and are named after the nearest postal village, which are centuries old. But a Dragon Rapide or a Bristol Bulldog from that period had a very small noise profile. When the big-props and the jets arrived the noise levels increased hugely, but the residents weren't given any concession. Society was required to adapt to the new noise and pollution levels in the name of progress. And now the operators have the audacity to complain about local residents complaining. If you really want to operate 24/7 in a drone-free environment, go and build an offshore island airport.
  - sandworm101 8y ago
    Our helos are over 55 years old. Not many residents have been here that long.
4ad 8y ago
> When the article says [...] they are speaking of power Who knows what they are speaking of, it's a very poorly written article. > The distance between the ridges are roughly equivalent to the wavelength of the airport noise, which is about 36 feet. What. The airport noise is broadband noise, it doesn't have a definite wavelength. 36 feet means a frequency of 31Hz. 31Hz is not even the dominant frequency[1]... [1] https://www.ndt.net/article/jae/papers/26-290.pdf https://www.ndt.net/article/jae/papers/26-290.pdf

by jws 8y ago

sandworm101 8y ago

I work with aircraft (big helicopters) and field noise complaints. I find time of day and weather mean far more than actual noise energy. 7pm, sunset, calm wind, sunday = noise complaint. We never get complaints at 11am on a windy or rainy tuesday. I am very polite on the phone, but if you choose to retire beside an AIRBASE! Our helicopters have been flying over your house decades before it was ever a house. Sue your real estate agent for not telling you exactly why zoning limits your neighbourhood to two-story non-commercial structures.

Washuu 8y ago
Weather does have an affect on noise along with the differential between air temperature near the ground and higher up. It is common for the local government testing facility to send out notices to expect louder than normal booms from rocket testing during different weather.
- sandworm101 8y ago
  I dont think it is physics. People are eating dinner outside in good weather. There is also a group dynamic. Some people call on speakerphone and it is obvious they are just showing thier dinner guests that they know my phone extension. That senario, the likelihood that people are eating dinner as a group outside, is the best means of prediction. We alter our operations as best we can accordingly. There is a common joke in air forces, at least western air forces: Plane to loud? Did you see a red star on it? You're welcome.
  - DonHopkins 8y ago
    My President's too loud, and I think there's a red star on him.
  - Washuu 8y ago
    Some sources that can explain it better that I can: https://physics.stackexchange.com/questions/255844/do-clouds-reflect-ambient-noise https://physics.stackexchange.com/questions/255844/do-clouds... https://physics.stackexchange.com/questions/133198/why-do-i-always-hear-remote-train-horn-at-night/133207#133207 https://physics.stackexchange.com/questions/133198/why-do-i-...
michaelbuckbee 8y ago
I live in the Hampton Roads area and realtors are very up front about jet noise and crash danger. There are maps of high and low noise areas, you are asked to sign a waiver stating that you are aware your home is in a high noise area, etc.
sandworm101 8y ago
The difficulty is that helo operations are pushed around by the bigger/faster stuff. So it might be years before a combination of wind, weather and traffic cause us to approach/depart over a particular neighborhood. In an emergency, a SAR callout, we will fly over areas that might never have seen a flyover before.
dingaling 8y ago
> but if you choose to retire beside an AIRBASE! The problem with that position, at least in the UK, is that the social contract between the airport operator and the local residents was never revisited. Most of the UK's airports and airbases date from the 1920s and 30s and are named after the nearest postal village, which are centuries old. But a Dragon Rapide or a Bristol Bulldog from that period had a very small noise profile. When the big-props and the jets arrived the noise levels increased hugely, but the residents weren't given any concession. Society was required to adapt to the new noise and pollution levels in the name of progress. And now the operators have the audacity to complain about local residents complaining. If you really want to operate 24/7 in a drone-free environment, go and build an offshore island airport.
- sandworm101 8y ago
  Our helos are over 55 years old. Not many residents have been here that long.

4ad 8y ago

> When the article says [...] they are speaking of power Who knows what they are speaking of, it's a very poorly written article. > The distance between the ridges are roughly equivalent to the wavelength of the airport noise, which is about 36 feet. What. The airport noise is broadband noise, it doesn't have a definite wavelength. 36 feet means a frequency of 31Hz. 31Hz is not even the dominant frequency[1]... [1] https://www.ndt.net/article/jae/papers/26-290.pdf https://www.ndt.net/article/jae/papers/26-290.pdf