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43 This chapter describes the conduct of noise measurements and interviews during July and September of 2015 in the cities of Long Beach, CA, and Las Vegas, NV, and during June of 2016 in Georgetown and North Arlington, VA, in the Washington, D.C., area. 4.1 Interviewing Areas, Helicopter Routes, and Noise Measurement Sites Figures 4-1 through 4-3 show nominal helicopter flight routes and noise measurement sites for the three interviewing areas. 4.1.1 Description of Long Beach Study Area The Long Beach study area was adjacent to the Redondo Avenue helicopter corridor, a vol- untary route shown on aeronautical charts for the area. The route extends from LGB, just north of the study area, to the coast. Upon reaching the coast, helicopters turn east or west to follow it further. The route supports two-way traffic for both approaches and departures. Overflown neighborhoods contain mostly single-family dwellings, with some small apart- ment buildings dispersed throughout the neighborhood. Redondo Avenue is a commercial street for the most part, with a few small commercial buildings scattered elsewhere throughout the study area. Homes in the study area range from classic California cottages built in the 1920s and 1930s, to mid-century small apartment buildings. Housing on streets nearer the coast is more expensive than elsewhere in the study area, while areas to the north of the study area con- tain more modestly priced homes. The Redondo route is used for helicopter training, executive transport, tourism, and public safety flights. About fifteen overflights per day occur in the Redondo Avenue corridor, split about evenly between northbound and southbound flights. For the sake of completeness, Figure 4-1 also shows the more lightly used Cherry Avenue corridor, which supports only about two overflights per day. Helicopter operations on both routes are generally flown at or about 500 feet above ground level (AGL) to avoid conflicts with nearby airport traffic. Noise measurement sites for the Long Beach interviewing area were selected with the assis- tance of airport staff knowledgeable about nearby airspace uses. 4.1.2 Description of Las Vegas Study Area The Las Vegas study area is composed largely of single-family homes constructed since the 1950s. The neighborhoods are typical low-density residential areas with a few condominiums C H A P T E R 4 Noise Exposure Estimation and Interviewing Methods
44 Assessing Community Annoyance of Helicopter Noise Figure 4-1a. Location of noise measurement sites at the Long Beach study area. Figure 4-1. Helicopter routes (white double-ended arrows) and noise measurement sites (red stars) in Long Beach study area.
Noise Exposure Estimation and Interviewing Methods 45 Figure 4-2. Helicopter route (white arrow) and noise measurement sites (red stars) in Las Vegas study area. Figure 4-2a. Location of noise measurement sites at the Las Vegas study area.
46 Assessing Community Annoyance of Helicopter Noise and no distinctive features. Ground elevations on the west side of the study area are essentially the same as the airport elevation, but the terrain drops considerably on the east side of the study area. The area along Tropicana Avenue is generally commercial, with homes located behind commercial development. Interviews were conducted with residents of homes along the Tropicana Avenue helicopter corridor. The corridor is immediately to the east of LAS and the Las Vegas strip, as shown in Figure 4-2. It is a one-way departure corridor used primarily by air tour operators and some public safety helicopters. The corridor supports approximately 150 overflights daily. The heli- copter flight route is at an elevation of about 1,000 feet AGL in the western portion of the study area, but at greater altitudes AGL in the eastern portion (due to falling terrain). Residential land uses in the interviewing area are dominated by single-family detached dwellings, mixed with a smaller number of condominiums. Noise measurement sites were selected by door-to-door canvassing in a single-family residen- tial area adjacent to Tropicana Avenue. The neighborhood includes many fenced private yards, in which noise monitors could be securely installed and operated 24 hours per day. 4.1.3 Description of Washington, D.C., Study Area The Washington, D.C., study area was composed primarily of single-family homes dating from the 1950s to newer homes located in Northern Arlington and Georgetown adjacent to the Potomac River. The study area is shown in Figure 4-3. The neighborhoods in Northern Arling- ton have the appearance of suburban neighborhoods, without distinctive or unique features. A few condominiums and apartment buildings are also found in the study area. The Georgetown Figure 4-3. Washington, D.C., study area.
Noise Exposure Estimation and Interviewing Methods 47 interviewing area included a mix of retail uses, a university with a hospital heliport, and party wall (row) and single-family houses. Interviews were conducted within an area paralleling the Potomac helicopter corridor above the river. The helicopter flight paths are at an elevation of about 500 feet AGL to avoid airspace used by fixed-wing arrivals at DCA and a departure route from DCA that also follows the river. Helicopter noise exposure estimates were made by modeling rather than by direct measure- ment. Since the helicopter corridor is beneath heavily used departure and arrival corridors to DCA, any attempt to measure helicopter noise exclusively would be complicated by fixed-wing overflight noise. One of the unresolved issues is how well INM models BVI noise. As described in Chapter 5, aircraft noise exposure generated by fixed-wing traffic (primarily air carrier jets) at DCA exceeds noise exposure created by helicopters by about an order of magnitude in the interviewing area. 4.2 Noise Measurement Protocol Two sets of sound level meters were installed at each of the noise monitoring sites in both Long Beach and Las Vegas. The primary measurements were made using four Larson Davis 831 noise monitors. These meters continuously archived a time series of sound pressure levels at one-second intervals. The metrics collected by the 831 monitors included A-weighted 1 second Leq, C-weighted 1 second Leq, and 1 second Leq for each of the one-third octave bands from 6 Hz to 20 kHz. In addition, Larson Davis Model 824 meters at each site collected 1-second time histories of A-weighted and C-weighted Leq values. High-resolution digital audio recorders were attached to the audio outputs of the sound meters at each monitoring site. All meters were calibrated periodically before, during, and after the measurement period. Appendix D contains a more complete description of the measure- ment equipment, calibration, and measurement protocols. 4.3 Noise Modeling Methods 4.3.1 Long Beach DNL contours and DNL values at each respondentâs home were developed with INM 7.0d,15 using radar flight tracks obtained from each airport. At Long Beach, all flight tracks were obtained and then filtered based on altitude and passage through the study area. Although FAA has instituted unique radar squawk codes for helicopters operating in the LA basin, these were inconsistently used during the time of the survey. An observer was therefore sta- tioned at the south end of the Redondo corridor from 7:00 AM to 7:00 PM every day. The observer photographed and logged every visible helicopter overflight. Helicopter types were determined from these photographs, and used to assign types to each helicopter flight track database entry. Figure 4-4 shows the Long Beach radar tracks, while Figure 4-8 shows the INM modeled tracks. 4.3.2 Las Vegas In Las Vegas, helicopter operators have voluntarily agreed to use unique squawk codes. Due to high compliance by operators, LAS was able to provide helicopter-only flight tracks for just the helicopters using the Tropicana corridor. Since the Las Vegas flight track database included the helicopter registration number, this was used to look up the helicopter type and update the flight track database with each helicopter type.
48 Assessing Community Annoyance of Helicopter Noise Figure 4-4. Radar flight tracks for 1 week prior to and during Long Beach survey. 4.3.3 Washington, D.C. The DCA noise contours were generated using the INM study files previously developed for the âRunway Safety Area Improvements for Runways 15-33 and 04-22 Environmental Assessment.â FAAâs 2010 environmental assessment included year 2010 contours (based on actual operations) as well as a forecast contour for the year 2016. The 2016 contours for fixed- wing operations were used for current purposes. While a comparison of actual to forecast operations was not done as part of this effort, forecasting over such a short period is com- mon. No major changes in fleet mix or other operating conditions affected the 2016 forecast. A doubling or halving of the operations would be required to change DNL by 3 dB. A 40% increase in operations would only cause a 1.5 dB increase in DNL. The 60 DNL contour closed just short of the study area, so the flight tracks over the Potomac used in the model were compared with the more recent flight tracks. This was done both because the study area was outside the focus of the EA and because it was unclear what changes in tracks occurred with the recent change due to NextGen procedures. The tracks along the Potomac were slightly modified for this study to better conform to the radar data observed during the study period. The change was minor, but aligned the helicopter model flight tracks to conform better to the radar tracks.
Noise Exposure Estimation and Interviewing Methods 49 Figure 4-5. Radar flight tracks for 1 week prior to and during Las Vegas survey. 4.3.4 Modeling Process The flight track databases, updated with aircraft type, were used to determine the num- ber of operations by helicopter type, by time of day, and by the location of backbone flight tracks. Sub-track locations were developed from this information to model helicopter noise. Figures 4-4 and 4-5 show the radar flight tracks for Long Beach and Las Vegas, while Fig- ures 4-6 and 4-7 show the helicopter tracks along the Potomac River and fixed-wing radar tracks for DCA, respectively. Figures 4-8, 4-9, and 4-10 show noise modeled backbone and sub-tracks for each helicopter noise model run. The fixed-wing INM noise model run was done using the year 2016 INM Study that Ricondo and Associates undertook as part of the EA for the Runway Safety Area project for Metropolitan Washington Airport Authority (MWAA). The vertical profiles used for the helicopter modeling were based on the altitudes actually flown. The variations in average altitude for each study area were small. The altitudes were 550 feet AGL for LGB, 500 feet for DCA, and 1,037 feet for LAS. The profiles were the standard INM departure profiles, modified only to reflect level flight at the above altitudes and at the speeds given in the standard profiles for level flight.
50 Assessing Community Annoyance of Helicopter Noise Figure 4-6. Helicopter radar tracks during DCA survey.
Noise Exposure Estimation and Interviewing Methods 51 Figure 4-7. Radar tracks for fixed-wing aircraft, typical day during DCA survey (arrivals in red).
52 Assessing Community Annoyance of Helicopter Noise Figure 4-8. Noise model flight tracks for 1 week prior to and during Long Beach survey.
Noise Exposure Estimation and Interviewing Methods 53 Figure 4-9. Noise model flight tracks for 1 week prior to and during Las Vegas survey.
54 Assessing Community Annoyance of Helicopter Noise Flight tracks DEP- Blue APP- Red Legend 1 mi N Figure 4-10. Helicopter noise model tracks for DCA survey modeling. 4.4 Estimation of Noise Exposure Values to Survey Respondentsâ Homes Sampling frames prepared for each study area contained names and addresses for each household in the study area. This personally identifiable information was replaced by case numbers to comply with confidentiality requirements of the Institutional Review Board. Lati- tude and longitude coordinates then were coded into the noise model by case numbers. Point locations for respondentsâ residential addresses sufficed for purposes of calculating helicopter DNL values by case numbers and associated noise measurement locations. 4.5 Sampling Strategy Several steps were required to prepare sampling frames for each study area. The first step was to develop preliminary definitions of helicopter-only noise contour bands adjacent to helicopter flight tracks at each airport. INM noise modeling was used to define these noise contour bands. Eight such preliminary helicopter noise exposure bands, shown in Figure 4-11, were identified at LGB. Seven such preliminary exposure bands were identified at LAS, as shown in Figure 4-12. The sampling bands in Washington D.C. are shown in Figure 4-13. In each study area, households within the preliminary noise exposure bands were then identi- fied from information contained in the two telephone databases (landline and cell phone) by latitude/longitude coordinates for the street addresses. This measure permitted a count of the number of interview-eligible sites within each noise contour band. The same latitude/longitude
Noise Exposure Estimation and Interviewing Methods 55 Figure 4-11. Preliminary helicopter-only noise exposure bands in vicinity of helicopter flight tracks at LGB.
Figure 4-12. Preliminary helicopter-only noise exposure bands in vicinity of helicopter flight tracks at LAS. Noise contours Legend DNL 40-43 DNL 43-46 DNL 46-49 DNL 49-52 DNL 52-55 DNL 55 1 mi N © 2016 Googlegle Figure 4-13. Noise exposure bands for DCA helicopter noise survey.
Noise Exposure Estimation and Interviewing Methods 57 coordinates were later used by noise modeling software to refine the preliminary estimates of helicopter noise exposure for each respondent. The landline and cell phone databases were compiled from public records and proprietary databases.16 The first of the two databases contained telephone-subscribing households in a nationwide, U.S. landline database (generally known as âListed Landlineâ database). This database con- tains records of all known U.S. households subscribing to landline telephone service. A second database, containing records of wireless telephone subscribers, were drawn from a proprietary database of wireless phones containing more than 125 million wireless phones nationally. (The wireless phone database is one developed from data provided by cell phone users and collected by commercial users.) A joint sampling frame was constructed from the telephone-subscribing households within areas eligible for interview in the two databases, from which a stratified (by expected heli- copter noise exposure) random sample was then drawn. The LGB sample released for dial- ing contained 7,684 listed landline-subscribing households and 2,878 wireless-subscribing households. The LAS sample contained 4,688 listed landline-subscribing households and 3,135 wireless-subscribing households. The DCA sample contained 2,873 listed landline- subscribing households and 1,351 wireless-subscribing households. These were divided into replicates of 1,000 (listed landline) and 500 (wireless subscribing) telephone numbers for efficiency of use in computer-assisted telephone interviewing (CATI). In this context, rep- licate refers to a sub-sample of the entire database. The database was divided in these rep- licates for efficiency in achieving the minimum number of callbacks to each number where a respondent did not agree to an interview and to ensure no more calls were initiated than needed to achieve the sample goals. 4.6 Interviewing Procedures A single structured telephone interview was sought from an adult member of each house- hold within sample replicates released for interview contact attempts. The structured interview, introduced as a study of neighborhood living conditions, was based on a questionnaire contain- ing fifteen items. The questionnaire is reproduced in Chapter 3, Table 3-5. Questions posed to respondents are shown in black; closed response categories and codings for them are shown in blue; and instructions to interviewers are shown in red. CATI methods were used by a total of 152 trained and centrally supervised interviewers to make 18,385 interview contact attempts. As many as 15 contact attempts (an initial attempt fol- lowed by up to 14 callbacks at different times of day over a weeklong interviewing period) were made to households identified in the sampling frame. Interviewers sought to conduct an inter- view with any adult, verified household member. Fields (1993) has shown that demographic variables such as age, sex, social status, income, education, home ownership, dwelling type, and length of residence have no systematic effect on reports of noise-induced annoyance.
