A motion was made to elect a chairman for the Metrics Committee. Mary Rose nominated Bill Simpson. Melanie nominated John Sistarenik who declined the nomination. Billâs nomination was seconded and carried with the exception of Melanie. Melanie noted that there may be a conflict of interest due to Billâs working for UPS.
Marvin Pilkenton led a discussion of sound measurement. It was noted that five "metrics" were already in the scope of LFA. This group was charged to select two more.
Marvin and Melanie agreed that a metric must be included which measures vibrational damage. These metrics are "C" weighted metrics.
The committee discussed specifications of the two types of monitors shown in he handouts.
If was agreed that the monitors will be checked for calibration stickers.
The five metrics already selected by LFA are: Lmax, TA, SEL, Leq and DNL.
A call was made to LFA, Bill Willkie and Eric Bernhardt on the speakerphone.
A question was posed to LFA regarding the difference between ARTS data and Flight strips. Eric said that flight strips give info like time of day, runway split. Bill Willkie emphasized that ARTS data will show actual locations of aircraft.
A discussion ensued regarding the use of flight strips.
Melanie asked if we should have ARTS sampling before monitoring so we would know if the flight tracks are the way they were before monitoring. LFA said the tower will not know where the monitors are.
Bill Simpson asked LFA if the monitors have the capability to measure "C" weighted metrics. The answer was yes.
Melanie asked what the range of the monitors was. Bill Willkie answered if there is a community with a concern, put a monitor there. For instance in the northwest area of the airport one of our ten monitors will be placed to obtain information about a noise barrier.
Melanie asked if the monitor can measure all of the scales given. Bill Willkie answered yes. Melanie asked if all of these measurements could be taken simultaneously. Bill Willkie answered yes.
A discussion was held between Marvin and Bill Willkie relating to EPNDb, which is perceived noise used by aircraft manufacturers. Bill said this is used by aircraft manufacturers only and has no value for what we are looking at.
Melanie asked if weâll have access to raw data to which Bill Willkie answered yes. She asked Bill about the monitor battery only lasting 20 hours for a 24-hour study. Bill Willkie said they would have to go out and change the battery.
Bill Simpson asked what "perceived" noise level is. Bill Willkie answered that it is a metrics developed in the Î70âs to measure the "screech" of what are now older engines. The FAA found that dBA was a more accurate prediction of annoyance and chose it for its model.
Bill Willkie noted that if the committee wanted a "new" metric, it could use L10, a level that is exceeded 10% of the time or L90, same principal. He also noted that the SEL is used to examine the probability of waking someone up. The SEL is an entire event, a fly over, expressed as if it occurred in one second.
Tim Chilton asked why we donât use C-weighted metrics to draw contours and put it in the final report. Bill Willkie said we cannot plot contours from this data, only spots. INM does not support C-weighted metrics so we cannot draw contours from this data.
John Sistarenik asked if we did C-weighting at the 20 sites, without contour maps, could we report the data to show what structural damage might be? Bill answered that there is a well established structural damage threshold. Bill said he would be surprised if we reached that threshold. There has never been a case of structural damage. Bill Willkie said we could publish what the criteria are for structural damage and make it part of the report.
Bill Simpson asked about the problem with e-mail. Melanie said she figured out that it is a Windows problem ö she has Windows 95 and LFA has Windows 97.
Melanie asked if the data can be output to 55 DNL. Bill Willkie said yes, easily.