Noise Notes

Noise Notes
Attachment N to submissions to EDHCSD and other local agencies

For a quick glance summary click on any of these thumbnails to enlarge graphics. Text begins below the graphics. Also see Approach Logs.

From the Sacramento County Airport System:

Graphs of measured noise

Data tables for early morning arrivals
Feb. 2003 measurements	May 2004 measurements

Average L_max = 66.0 dB Minimum L_max = 51.5 dB Maximum L_max = 73.0 dB 4 of 13 approaches > 70 dB all < 75 dB One flight's L_max was "lost in ambient". This missing data point was not considered in determining minimum and average L_max.	Average L_max = 64.9 dB Minimum L_max = 60.4 dB Maximum L_max = 73.4 dB 4 of 31 approaches > 70dB all < 75 dB
Flight tracks, first two daily early morning approaches April 1 through May 22, 2008
ABX1927, south approach	UPS 956, ILS approach

Examples of comparison with environmental noise,
annotated graphically to show the range of SCAS maximum noise measurements
during air carrier cargo overflights of the El Dorado Hills west ridge:
Annotated copy of a chart published by the Oakland Airport

Cargo volume handled through Mather:
The trend in recent years, from FAA statistics
See Demand Forecast for additional information
Mather landed cargo

Personal notes by Paul Raveling:

To date I have found no evidence that air carrier approaches to Mather produce noise that would reasonably be considered "obtrusive" by a majority of El Dorado Hills residents. Actual freighter approach noise levels are in fact less than noise produced by many other sources in the community. Those other sources may include irregular overflights by business jets and possibly Air Force T-38s, but most noise sources are ground-based.

Noise, seeking evaluation by objective criteria

My personal search has included observing approaches by standing directly below the ILS approach path on Ridgeview Drive, at a point almost at the maximum elevation of terrain on the western ridge of El Dorado Hills. All such freighter approaches that I have observed were less noisy than surface traffic passing on the street. This is consistent with noise measurements done in the past by the Sacramento County Airport System and with multiple sources of noise comparison charts. The example supplied here is an annotated copy of a chart published by the Oakland Airport, showing the range of L_max sound levels recorded in SCAS noise measurements on the western ridge of El Dorado Hills. My subjective estimation of noise is consistent with SCAS measurements showing an average maximum sound level (L_max) of about 65 dB.

I correlated observations of specific approaches with their flight tracks by means of the WebTrak replay mode. In addition, I have reviewed (to date) more than 200 freighter approaches through WebTrak and have found no flight path deviations that would indicate potential for a significantly higher noise level. Rough estimation of noise level as a function of crossing altitude above ground level and throttle setting (indicated by descent rate) corresponds well to data published by SCAS from its noise measurements in 2003 and 2004. The 2004 data sample for 31 approaches in early morning hours showed an average L_max of 64.9 dB, a range of 62.2 dB to 71.0 dB for 85% of EDH overflights, and an extreme maximum level of 73.4 dB.

I have not yet seen a flight track likely to produce a moderate or high noise level (80 dB or more). I experienced one approach personally in May that involved circumstances that should have elevated its approach noise level, but its actual noise was low, probably about 70dB or slightly less. This occurred when a freighter inbound on the ILS was diverted about 3 miles to the north and directly overflew my home, passing precisely overhead. The distance added by the diversion required a reduced descent rate and a higher throttle setting than otherwise used on a 3-degree glide slope. The diversion was a very exceptional event, required by an air traffic conflict with an eastbound Piper Comanche.

Noise, subjective criteria:

Perception of noise as being excessive is subjective. There may be individuals with sensitivity that makes lower levels of noise a problem for them personally, even though the same level is not a problem for others. We, and especially local government, needs to identify the relative importance of noise sources as community issues and noise perception as either individual or community issues. Based on all evidence to date my current interpretation is that the actual problem probably is mainly an issue of individual sensitivity on the part of a relatively small portion of our population.

I hear contradictory reports about freighter noise, but press exposure typically goes to those that say "there is a problem" and not to those saying "there is no problem". Some reports are somewhat in the middle, generally of the form "yes, there's some noise, but it's not a problem". In my personal contact with people in El Dorado Hills I hear many more reports of no problem, with or without qualification, than of existence of a significant problem.

It would help to survey our residents with either random sampling or comprehensive sampling to gain understanding of the extent of impact based on subjective factors. A particular goal should be to identify whether we have a community issue, a subcommunity issue, or only issues for individuals.

A particular caution is that many in the public are not aware of actual circumstances because of news coverage of complaints. Examples:

In a show-of-hands question at an El Dorado Hills Citizens Alliance meeting 1 out of about 20 attendees responded to indicate that they experienced undesirable freighter approach noise. An alternate phrasing would be that 95% of the attendees had no problem with freighter approach noise.
Some in my own neighborhood have expressed concerns about freighter departure noise. However, no air carrier cargo departures overfly El Dorado Hills. Apparently past public exposure to complaints has led some portion of our population to assume that if they hear a jet it must be a freighter, and that if they hear a jet it must be a problem, regardless of actual noise level.
Part of the public discussion refers to multiple freighter overflights between midnight and 6 a.m. Actually, there are no freighter arrivals at all between about 9 p.m. and 3:30 a.m., and the first approach that overflies El Dorado Hills and Folsom usually is at about 4 a.m., except when it's delayed. On most days there are 3 morning approach overflights, almost always within the interval between 3:30 and 7:30. Occasionally there are 4, on 2 days each week there are 0.

An additional compelling need is for public agencies to recognize factual reality. All three of the El Dorado Hills Community Services District, the El Dorado County Board of Supervisors, and the City of Folsom have repeated claims that easily evident as being factually incorrect. All three have demonstrated lack of knowledge which is essential to being able to work cooperatively and productively on this public issue.