Meeting Notes : Noise Monitoring Committee
Committee notes reflect the views and opinions of the committee members and not necessarily those of the Noise Compatibility Study Group, Coordinating Council, Regional Airport Authority of Louisville and Jefferson County, or the Consultant Team.
Pending Committe Approval
at RAA Board Room
The meeting was started at 7:50. An attendance list is included with these notes.
After those present introduced themselves, Bill Willkie of LFA began to answer the questions that a subcommittee of the Monitoring Committee had given LFA on December 2,1999. (The memo to LFA is included with these notes.)
• Please explain why the Lmax points that are graphed don’t seem to match those in the raw data in some cases. Here is a specific example:
Site 1-National Turnpike, on 6/3/99 at 12:00
Lmax in the data is 93.5 and Lmax on the graph is about 80.
Bill said that, if there were any discrepancies, that these were errors. He said that the graphs were drawn by people taking data from spread sheets and it’s possible that some errors could occur.
Other issues were discussed after this question was answered.
Bill said that the general guideline is that monitored results should be less than 3 db divergent from INM predicted values in the 70 Ldn contour and less than 5 db divergent in the 65 Ldn contour. This didn’t happen in some monitored sites south of the airport. LFA determined that this was due to the 747 cargo planes weighing more on take-off than was reflected in the variables used in the INM. He said that the variables were manipulated to account for the actual weight and new contours were drawn. These new maps will be distributed at Study Group Meeting #4.
In answer to several questions from committee members, the following things were discussed:
The Ldn is based on an annual average.
There is a 10 db penalty for night time(10 p.m.-7 a.m.) noise.
Noise from behind planes as they take-off is accounted for in the INM.
If shielding (from houses or other structures) is lost, ground noise could
increase. This new noise could be monitored to determine the increased level.
Taxiing noise and engine run-ups are not taken into account in the INM.
A 65 db threshold was used on the noise monitors to screen out non-aircraft noise. This caused some distant planes to be”missed” by the monitors.
Noise from the cross wind runway is included in the annual averages.
It is traditional for air traffic controllers to accommodate pilots requests.
If an aircraft has an SEL loud enough to cause awakenings outside the 65 Ldn contour, it would do the same thing at other airports.
Bill gave a list of the variables that go into the INM. They are: fleet mix, load, weight (including fuel), number of aircraft, runway use, flight tracks, profiles, average temperature, and elevation. INM does not take into account cloud cover or humidity.
Bill answered the other sobcommittee questions.
• What is the difference in the interval report and the exceedance report and which is plotted in the graph?
The exceedance report lists all events that exceeded the threshold. He wasn’t sure about the interval report, but will get back to us. He said the table listed all events that could be positively matched with an event in the ARTS data. If an event wasn’t matched, it was usually because the source could have been more than one plane.
• Why would some monitored Ldn values be above or below the INM predicted values?
This question had already been covered.
• What kind of correlation does it take for the monitored values to verify the INM?
Values of +/- 5 db in 65 Ldn contour.
• Is there a statistical variation around each contour line?
There is no statistical variation around a contour line.
• Why does the 2005 map contour not take monitored data into account?
You can’t monitor for 2005. The question was withdrawn.
• Is there a way that Lmax is calculated into overall analysis?
Lmax and SEL are looked at and considered as supplemental information.
Bill agreed to answer these questions at the end of Study Group Meeting #4 for anyone who is interested.
The committee was concerned about zoning restrictions and avigation easements on land in the 65 Ldn contour. It was agreed that these concerns would be passed on to the Relocation Committee.
The committee agreed that some monitoring should continue after procedures are approved. It was suggested that the committee could decide what monitoring could do for enforcement of procedures.
The next meeting will be scheduled and announced. This meeting ended at 9:40.