JOHN WAYNE AIRPORT ORANGE COUNTY AGENDA STAFF REPORT ATTACHMENT A RESULTS OF THE SIDE-BY-SIDE COMPARISON OF NOISE MONITORING SYSTEMS

Transcription

1 JOHN WAYNE AIRPORT ORANGE COUNTY AGENDA STAFF REPORT ATTACHMENT A RESULTS OF THE SIDE-BY-SIDE COMPARISON OF NOISE MONITORING SYSTEMS September 22, 2015 Page 1 of 33

2 JOHN WAYNE AIRPORT RESULTS OF THE SIDE-BY-SIDE COMPARISON OF NOISE MONITORING SYSTEMS Prepared by: Landrum & Brown Fairchild Road, Suite 230 Irvine, CA July 7, 2015 Page 2 of 33

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4 JOHN WAYNE AIRPORT RESULTS OF THE SIDE-BY-SIDE COMPARISON OF NOISE MONITORING SYSTEMS TABLE OF CONTENTS 1. Background History Comparing the Old and New Systems Background on Noise Measurement System Performance Requirements Calibration of the New and Old System Installation of Side-by-Side Systems Methodology Results Analysis of Results Recommended Adjustments...17 Appendix 1. Calibrations and Cross-checks...19 Appendix 2. Statistics and Measurement Uncertainty Appendix 3. Photographs of Monitor Sites...26 LIST OF EXHIBITS AND TABLES Exhibit 1. Noise Monitoring Locations...6 Table 1. The Margin Available Shown in dba for Class E Noise Levels...9 Exhibit 2. Pistonphone and Coupler Used to Calibrate Hydrophone...11 Exhibit 3. Sketch of Microphone Setup...12 Table 2. Comparison of SENEL Values From Old and New Systems...14 Table 3. Recommended Adjustments to the Phase 2 Access Plan Noise Limits...17 Table 4. Recommended Adjustments to the General Aviation Noise Ordinance...18 Table 5. Summary of Estimations of Measurement Uncertainty...25 Page 4 of 33

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6 John Wayne Airport, Orange County Side-by-side Comparison of Noise Monitoring Systems Results 1. Background In early 2015, a new noise monitoring system was installed at John Wayne Airport, Orange County (SNA) (JWA or Airport) to replace the current noise monitoring system that was installed at JWA in A side-by-side comparison of the noise levels as recorded by the new system and the current system was conducted commencing March 1 through May 31, The purposes of this report are to present information regarding the current and new noise monitoring systems and provide the results of the side-by-side measurements for the new noise monitoring system at the Airport. Based on the data collected during the side-by-side measurements, this report also makes recommendations for appropriate technical adjustments to the maximum permitted noise levels at the Airport in order to maintain parity with the existing noise compliance limits and to preserve operational capacity at JWA. The new Bruel & Kjaer (B&K) noise monitoring system was recently installed by BridgeNet International (BridgeNet) to replace a system that was installed in 1997 by the company then named Tracor, Inc. Tracor was acquired by other firms and is now owned by Exelis, Inc. and will be referred to as the Exelis system throughout this report. The new system is needed because of the age of the existing system and resulting difficulty in securing replacement parts and servicing and repairing the existing system. In addition, the marine environment in the vicinity of the departure noise monitors causes corrosion in both the hardware and electronics. The Exelis system consists of noise monitors and microphones unique to the Tracor systems of the time and were designed and manufactured by Tracor. All of the engineers who designed and built the Tracor system have retired and parts are no longer manufactured. In addition, the technology has improved dramatically since the 1990 s, particularly in the speed and reliability of transferring the data from the field microphones to a central processing location, such as the noise office at the JWA administration building. Given the critical role the noise monitoring system plays in the enforcement of the JWA Phase 2 Commercial Airline Access Plan and Regulation (Access Plan) 1 maximum permitted noise limits and other operational regulations and restrictions as well as the County of Orange General Aviation Noise Ordinance (GANO), maintaining a reliable and state of the art system is very important to the County and communities surrounding the Airport. 1 Phase 2 Commercial Airline Access Plan and Regulation, County of Orange, October 1, 1990 as amended. 3 Page 6 of 33

7 Although, both the existing Exelis system and the new B&K system meet international standards for Precision Sound Level Meter performance, these standards have specified tolerances that, for practical reasons, are greater than zero. Therefore, simultaneous side-by-side measurements will agree with certainty only to within the specified tolerances of the standards. These tolerances vary by frequency and by orientation of the microphone. The relevant national and international standards for these devices are described later in this report. The side-by-side comparison of the noise levels recorded by the new system and the current system was designed to ensure that the Access Plan and GANO grandfather status is not jeopardized in any way. Essentially then, the objective of the side-by-side comparison process is to ensure that the Airport can maintain parity with the existing noise compliance limits at the Airport and preserve operational capacity at JWA as presently defined in the Access Plan. 2. History The original Exelis (formerly Tracor) system was installed in In 1997, JWA entered into a contract with Exelis to install a new noise monitoring system at JWA to replace the original system. In late 2014, the Board of Supervisors authorized JWA to enter into a contract with BridgeNet to install a new system, to be completed by Fall of The 1997 and 1979 systems included hydrophones (underwater microphones) as microphones and dedicated telephone lease lines to transmit data to the JWA Access and Noise office. The original use of hydrophones in the 1970 s was done to ensure that moist salt air effects did not compromise the collection of noise data. The microphone portion of the noise monitoring system is by far the most delicate part of the system. Since the original installation, outdoor systems that use true microphones have been developed and have proven to operate in all outdoor environments, even ones more extreme than the rather mild, but salty, environment around JWA. Dedicated telephone lease lines were the only option in the 1970 s to connect the microphones with the data collection point and were still prevalent in the 1990 s, but are unreliable and expensive to maintain. These require paying the local telephone service provider for a dedicated wire from the microphone through the telephone switching network into the noise office. If the line goes down, there is no communication with the monitor until the line comes back into operation. The field monitors can store data for up to fourteen days, but the data is stored on the noise monitoring station (NMS) pole, not in the office where it is needed on a real-time basis. Modern connections do not rely on dedicated telephone lines, but instead use cellular technology to communicate to the central office or internet 4 Page 7 of 33

8 connections. While these systems can also go down, the troubleshooting and repair process is much simpler and more straightforward. 3. Comparing the Old and New Systems The new system is designed to update and modernize the current noise monitoring system. Ideally, the new system and the current system would measure the exact same level for each noise event. However, such accuracy 2 is not technologically feasible. Such systems normally have end-to-end tolerance of plus-or-minus 1.5 decibels (db). The question of why different systems measure differently is explained in more detail later in this report. Given these differences, and in order to obtain relevant noise data upon which the County could compare the new noise monitoring system with the current noise monitoring system, the County conducted a three month side-by-side comparison of the two systems from March 1, 2015 through May 31, 2015 at representative monitoring sites (1S, 2S, 3S, and 8N). These sites are shown in Exhibit 1. 2 Accuracy is a poorly defined concept in measurement science and the industry has standards that recommend this concept of accuracy is better described by the term measurement uncertainty. Uncertainty is the preferred terminology and will be used here to mean what people commonly think of as accuracy. 5 Page 8 of 33

9 Exhibit 1: Noise Monitoring Locations 6 Page 9 of 33

10 The methodology used in the current side-by-side comparison was modeled after the process that was conducted for the same purpose. That comparison process led to an increase of the noise limits at all noise monitors (for certain classes of aircraft) in order to maintain parity with the original 1970 s system. The 2015 comparison process differed slightly from that conducted in In the previous review, side-by-side comparisons were conducted for a full year at all ten monitors. The reasons for structuring the side-by-side comparison process differently are discussed below. The 3 Month Time Period Among the lessons learned in the comparison process was that the data stabilized to a consistent result within the first month of testing. The overall uncertainty of any measurement, including the difference between measurement systems, is highly dependent on the sample size. Given the 100+ average daily operations at the Airport, attaining a large sample size does not require a year s worth of testing. A three month period was determined to be adequate to reliably identify any system differences. The period from March 1 through May 31 was selected because it is typically the quarter in which the highest noise levels are recorded. The test does include two months of the spring quarter. Note that the spring quarter is probably the loudest quarter because of weather conditions. The phenomena we know as May grey and June gloom, caused by the marine layer that pervades during this period, coincides with temperature inversions (temperature increasing with altitude) that cause bending of sound waves back towards the ground. While this causes the highest noise levels on the ground, it should not affect the differences between the systems. The spring quarter is of interest to the air carriers as it is the period that the carriers have the most difficulty meeting the more stringent Class E noise limits. Appendix 2 includes a description of the statistics and uncertainty of measurement for the difference calculation results. The measurement uncertainty is shown in Appendix 2 is quite low indicating that this 3 month comparison period is sufficient for a statistically reliable result. Selection of Sites to Compare In the comparison process of the noise levels, the side by side monitoring process included all ten (10) noise monitors. At that time, not only were the noise monitors replaced, but some sites were moved (4S, 5S and 6S) and a correlation of the new location to the old location needed to be established. An amendment to the Settlement Agreement was also approved to reflect these modifications. So the process involved more than just an equipment change. In addition, in 1997, there were three (3) categories, or Classes, of aircraft noise 7 Page 10 of 33

11 limits: Class A, Class AA and Class E. Class AA was eliminated from the noise and access restrictions at the Airport in connection with the settlement amendment and approval process and only Class A and Class E noise and access restrictions remain at the Airport. In terms of noise, today s quieter aircraft fleet meet the Class A noise limits by a very large margin. For the quarter ending June 30, 2014, the latest spring quarter for which data are available 3, the closest any air carrier came to the Class A noise limits was within 3.1 db of the limit at monitor 3S. The reality is that no air carrier currently operating at the Airport is at risk of violating the Class A noise limits with the current modern fleet (the MD80 was the last aircraft that was constrained by the Class A limits and it has not operated at JWA on a regular basis since 2008). Because Class E noise limits are more stringent than the Class A noise limits, the aircraft that operate in this category tend to operate closer to the Class E limits, particularly the larger air carrier aircraft. Currently, of the larger aircraft, only the B operate in Class E. Historically the B and A320 have operated in Class E with even smaller margins to the noise limits. Table 1 shows the margins available during the spring quarter of The limiting monitor is 3S and the B operated just 1 db less than the noise limits at this monitor during the spring quarter of There have been quarters in past years when the margin was a little as 0.5 db due to weather. Note that for Class A operations, the typical margin available ranges from 3 db to 12 db. The replacement of the existing noise monitoring system with the new noise monitoring system has the most potential to impact measurements at site 3S for Class E operations. In deciding where to conduct the side-by-side comparison, it was clear that 3S was the most critical location. The decision was made to include monitors 1S and 2S because it is at these monitors where some older aircraft and those that delayed their cutback altitude have historically come within the closest margins of the Class E limits. Sites 1S and 2S now have a larger margin between the Class E limits and measured noise levels, but in an abundance of caution they were included in the study to accommodate any future unknown procedure or aircraft changes. Because newer technology aircraft are quieter than existing aircraft, sites 4S, 5S, 6S, and 7S are not expected to be aircraft limiting monitors 4. While the air carrier Class A and Class E noise limits do not apply at the northern sites (8N, 9N, and 10N), site 8N was also included to ensure that the comparison captured any differences to the north and due to the fact that the GANO does apply for night operations and 8N is the location where such a violation is most likely to occur. 3 John Wayne Airport Noise Abatement Quarterly Report For April 1 through June 30, Aircraft limiting monitor means a noise monitor where compliance is so difficult that it precludes an aircraft type from operating at the airport due to inability to meet the noise limits. 8 Page 11 of 33

12 Table 1: The Margin Available Shown in dba for Class E Noise Levels Source: Quarterly Report April 1 through June 30, Background on Noise Measurement System Performance Requirements Airport noise measurement systems are complex systems that are designed to consistently measure the noise levels associated with aircraft operations. While these systems report noise levels in tenths of dbs, there are in fact varying degrees of instrument quality. The purpose of this section is to describe national and international standards or regulations that define sound level measurement instrumentation requirements. American National Standards Institute/International Electroacoustic Commission (ANSI/lEC). At the heart of an airport noise measurement system are measurement components that correspond to a sound level meter. The performance of sound level meters is defined nationally by ANSI and internationally by lec. Sound Level Meters are classified as Class I or Class II, with Class I corresponding to the more stringent precision sound level meter requirements. The accuracy specification varies in each of these Classes by acoustic frequency, with wider tolerances at lower and higher frequencies and the tightest tolerances in the middle frequencies. There are various requirements including frequency response, directional response and linearity. These vary with frequency, but as an example of the strictest requirements for Class I Sound Level Meters, the required tolerance in the middle frequencies (covering the dominant frequencies of aircraft noise) is plus-or-minus 1.1 db in terms of frequency response and linearity and plus or minus 1.3 db for directional characteristics for a noise within plus or minus 30 of vertical relative to the microphone. These requirements increase, i.e., become less strict at higher and lower frequencies. The directional characteristics relax dropping to plus or minus 1.8 db at 90 to the microphone direction. The significance of this discussion is that precision sound level meters, which are at the heart of the JWA noise monitoring system are subject to and require compliance to international standards for these types of instruments and the tolerances permitted are on the order of 1 db. State of California, Airport Noise Regulations. The State of California has adopted noise regulations for civilian airports. As part of that regulation, the State 9 Page 12 of 33

13 provides minimum requirements for an airport noise monitoring system. California is the only state or government agency to adopt such a requirement. The California requirement is that the end-to-end system accuracy of an airport noise monitoring system be plus-or-minus 1.5 dba 5. Society of Automotive Engineers (SAE). The A-21 Subcommittee of SAE develops and publishes aviation noise measurement and prediction recommended practices (Aerospace Recommended Practice - ARP). The practices published by SAE are used internationally and nationally. SAE has published Aerospace Recommended Practice, ARP, 4721, "Monitoring Noise From Aircraft Operations In The Vicinity of Airports." The SAE document, considered to be a best practices document, recommends that airport noise monitoring systems have an end-to-end accuracy of plus-or-minus 1.5 dba. International Standards Organization (ISO). ISO has published ISO 20906, Unattended Monitoring of Aircraft Sound in the Vicinity of Airports. This standard is of relevance here because it includes Appendix B entitled Uncertainty of Reported Data. Included in this Appendix is an example of the measurement uncertainty for measurement of a single Sound Exposure Level (SEL), numerically equivalent to the Single Event Noise Exposure Level (SENEL) that is the basis of the JWA noise limits. In particular, Appendix B identifies the directional characteristics of the microphone as the weakest part of the measurement system. 5. Calibration of the New and Old System Calibration and Traceability. In order to maintain the accuracy of any sound level measurement system it must be calibrated. That calibration should be traceable to national and international standards, i.e., reference microphones. The current system and the new B&K system were calibrated with a B&K Model 4228 Pistonphone. The old system was calibrated using pistonphone serial number and the new system used pistonphone serial number Separate pistonphones were used because the hydrophone on the old system requires a special acoustic coupler to match the hydrophone to the pistonphone. Exhibit 2 shows photos of the pistonphone and coupler used for the hydrophones. These pistonphones have a manufacturer's stated accuracy of plus-or-minus 0.15 db at the calibration frequency of 250 Hertz. It is important to note that the 5 dba refers to the A-weighted decibel. All measurements and rules at JWA use the A-weighted decibel which includes a frequency weighting that matches the human ear response to various frequencies. The human ear is not as sensitive to very low and very high frequencies as it is to the middle frequencies. The A- weighting accounts for this. 10 Page 13 of 33

14 calibrator uncertainty, less than 0.2 db is not indicative of the overall accuracy of the system. The calibrator provides only one level and one frequency in a plane normal to the microphone. In the real world the system measures a wide range of levels and frequencies at angles 90 to the microphone to directly overhead. The calibrator certificate for each pistonphone is provided in the appendix. Exhibit 2: Pistonphone and Coupler Used to Calibrate Hydrophone (top: calibrator and coupler, bottom: coupler disassembled) The two pistonphones were cross checked by removing the acoustic coupler from the pistonphone used for the old system and measuring the response on a single B&K sound level meter. The two (2) pistonphones matched within 0.02 db. A memo describing this test is provided in Appendix Page 14 of 33

15 6. Installation of Side-by-Side Systems All four (4) monitor sites had a similar type of installation. The existing top of the NMS pole (generally 20 feet high) was modified with a horizontal extension four (4) feet long. At one end, the B&K microphone was attached and at the other end a counterbalance was attached. The Exelis hydrophone remained in place in line with the NMS pole. This distance was selected to keep the microphones in the same sound field, but far enough apart that they did not shield one from the other or be the source of a sound reflection from one to the other. Given the general slant range distance from the microphones to the nearest aircraft, the approximate two foot separation would not result in any significant difference in aircraft sound measured (non-aircraft noise sources near the microphone, such as a lawn mower at the base of the pole, may be measured differently by each microphone). A diagram of the installation is provided in Exhibit 3. Pictures of the noise monitors fitted with the new and old microphones are shown in Appendix 3. Exhibit 3: Sketch of Microphone Setup 12 Page 15 of 33

16 7. Methodology Collection and Analysis of Side-by-side Data Data used to compare the results of noise measurements were collected from both the new and the existing system and were statistically analyzed to determine the net difference between the systems. The data from both systems included SENEL data for each aircraft operation including aircraft type, airline, flight number and the time of the maximum noise level. In each case, the time of the maximum noise level was used to correlate the new data to the old data. The data collected from the current and new systems were then analyzed by building a database. Flight information, SENEL data, and the time of the Lmax 6 at each NMS were included in the database. A database program was written to search the times of the Lmax of the new data for noise events that correlate with the times of the Lmax of the current system data. When a correlating event was found, the new system SENEL data and times were used to populate the database with the new system data. The database developed for this analysis consists of over 66,000 aircraft operations, including general aviation operations, covering the three month period March 1, 2015 through May 31, 2015 for sites 1S, 2S and 3S. At site 8N, a problem with the microphone and calibration was discovered and fixed on April 13, Therefore the site 8N data are for the period April 14, 2015 through May 31, Once this database was developed, the energy average SENEL values for each NMS for the current system and new system were calculated. The reported difference was calculated by subtracting the current system energy average SENEL from the new system energy average SENEL. The results are reported in Section Results The results for the side by side comparison are presented in Table 2. The data included in Table 2 includes the measurement site, the aircraft type, the noisebased Class designation for that aircraft type, the energy average SENEL for the old and the new system, the number of measurements, and the change in SENEL resulting from the use of the new system. The results show that based on aircraft type and location of the noise monitor station, the new noise monitoring system measures higher noise levels than the current noise monitoring system. The difference between the noise levels measured side-by-side at the current and new system ranges from 0.3 to 0.9 db. These results are discussed in more detail in Section 9. 6 Lmax refers to the maximum noise level of a noise event. During an aircraft flyover the Lmax is the sound level at the noisiest moment of the flyover. 13 Page 16 of 33

17 Table 2: Comparison of SENEL Values From Old and New Systems Site Aircraft Aircraft Class Existing SENEL (energy averge) New SENEL (energy averge) Count Change* 1S A306 A S A30B A S A319 A S A320 A S A321 A S B734 A S B737 A & E S B738 A S B752 A S CRJ7 E S CRJ9 E S A306 A S A30B A S A319 A S A320 A S A321 A S B734 A S B737 A & E S B738 A S B752 A S CRJ7 E S CRJ9 E S A306 A S A30B A S A319 A S A320 A S A321 A S B734 A S B737 A & E S B738 A S B752 A S CRJ7 E S CRJ9 E N A306 A N A30B A N A319 A N A320 A N A321 A N B734 A N B737 A & E N B738 A N B752 A N CRJ7 E N CRJ9 E * A positive change means new SENEL measurement is louder than the existing measurement.x Largest difference for Class A aircraft for sites 1S, 2S, and 3S.y Largest difference for Class E aircraft for sites 1S, 2S, and 3S General Aviation Aircraft Note that the general aviation recommended changes were based on an analysis similar to the air carrier analysis described earlier. The results showed that for the general aviation aircraft the differences for the new monitors were 0.3, 0.7, 0.3, and 0.4 for sites 1S, 2S, 3S, and 8N respectively. These numbers are very similar to the air carrier numbers. There may be some bias in the general aviation results as only a small fraction of general aviation operations trigger a noise event at the monitors. Thus the measurements reflect the results only for the 14 Page 17 of 33

18 louder aircraft and not the fleet as a whole. For example, in 2014 there were about 187,000 general aviation operations (93,500 arrivals and 93,500 departures). Yet during the 3 month side-by-side comparison only about 9,000 general aviation noise events were triggered out of total possibility of 23,375 (1/4 of 93,500) possible general aviation flights during those same 3 months or about 40 percent. It should be noted that of the 187,000 annual general aviation operations, 87,000 are touch and go operations that use the short runway and never overfly a noise monitor. The remaining general aviation operations use either the main runway or the short runway depending on aircraft size and air traffic control factors. To avoid the uncertain effect of the bias associated with the general aviation aircraft that did not trigger a noise event, the curfew noise limits for general aviation aircraft were adjusted using the 0.7 and 0.9 db adjustments to ensure that no change in the access restriction stringency occurs. The recommended adjustments to the GANO limits are presented in Section Analysis of Results Ideally, the new system and the current system would measure the exact same level for each noise event. However, in the real world such accuracy is neither feasible nor likely. These systems are considered precision instruments and have end-to-end tolerance of plus-or-minus 1.5 db. Theoretically, when comparing two systems each with a tolerance of plus-or-minus 1.5 db, the difference between the systems could be as large as 3 db. This would occur when each system is operating just within tolerance, each at the opposite end of the acceptable tolerance range. The question of why the systems measure different levels, even though each has been properly calibrated, is complex and in some areas not fully understood. Typically, there are three general explanations that must be considered. These include the following: * Calibration Considerations * Microphone Considerations * Electronic System Considerations Each of these is discussed in the following paragraphs: Calibration Considerations - The major calibration consideration is that while calibrator tolerance is quite small, the difference is non-trivial. The current Exelis and new B&K systems were calibrated with different calibrators, each with a tolerance of plus-or-minus 0.15 db. The two piston phones were tested side-byside with a common microphone and sound level meter (see Appendix 1 for details). The calibrators matched to within 0.02 db. However, the Exelis hydrophone requires an acoustic coupler, shown in Exhibit 2, to couple the calibrator to the hydrophone. This coupler is over 30 years old and through use 15 Page 18 of 33

19 may have worn to an extent that it may not fit as well as it did when initially built. Microphone Considerations - The microphone is the most sensitive and complex mechanical part of the system. Each microphone is subject to variation in response to the frequency of the sound source, the direction of the sound source, ambient temperature and humidity, and influence of electric and magnetic fields. An instrumentation microphone is measuring very fine differences when trying to differentiate sound levels by tenths of a decibel. For example, sound pressure levels of 80 dba (a typical maximum noise level for these test data) is measuring an absolute pressure of about pounds per square inch. A sound pressure level of 80.1 dba corresponds to pounds per square inch. This difference of pounds per square inch is the difference that must be measured to have a precision of 0.1 db. Note that industry standards for measuring sound pressure level is not in absolute pounds per square inch, but root mean square sound pressure measured in Pascal's 7. Pounds per square inch is used here so the reader can relate to the extreme sensitivity required of an instrumentation microphone. While the microphone required tolerances in terms of frequency response (measuring low frequencies as well as high frequencies), dynamic range (measuring quiet sounds as well as loud sounds), and linearity (measuring the same change in pressure at quiet and loud levels equally) are quite stringent, the required directional characteristics are limited by practical considerations and are in fact the weakest part of the microphone. Consider a microphone pointed vertically straight up. When an aircraft flys over that microphone directly overhead the microphone is at its most accurate. When an aircraft is measured directly horizontal to the microphone, such as is measured just as the aircraft takes off, the microphone is permitted to have a larger uncertainty in international standards (IEC 61672). For measuring SENEL, which is a kind of sum of noise as the aircraft is measured from the takeoff point (horizontal to the microphone) and gets closer until it passes overhead (vertical to the microphone) and then flys farther away decreasing its relative angle to the microphone. This sum of noise we call SENEL is subject to varying levels of uncertainty of measurement because the relative angle to the microphone is constantly changing. Because the highest uncertainty is when the aircraft is near the ground at the start of such a noise event (or the end of a noise event for landing) the noise level measured at the start and end of the event will have noise levels with greater uncertainty than when overhead. Electronic System Considerations - The signal delivered from the microphone is amplified in a pre-amplifier, converted to a digital signal in an analog-to-digital converter, and then the A-weighted amplitude is determined. The frequency response of each of these components can introduce variations that result in two different instruments measuring a slightly different level for the same sound source. 7 A Pascal is a metric unit measure of pressure, Newtons per square meter analogous to pound per square inch. 16 Page 19 of 33

20 JWA Noise Restrictions - While the comparison to absolute standards is interesting and verifies the system s compliance to state, national, and international standards, it is the comparison of the new system to the current system that establishes the recommended adjustments to the Access Plan and GANO noise limits to ensure that the Airport can maintain parity with the existing noise compliance limits at the Airport. In summary, the differences in the two systems are likely the result of a number of small factors, with the directional characteristics of the microphone versus the hydrophone being the largest single cause. 10. Recommended Adjustments to the Phase 2 Access Plan Noise Limits and the General Aviation Noise Ordinance in order to Maintain Parity With the Existing Noise Compliance Limits at the Airport. Based on the results of the side-by-side measurements, the recommended adjustments in the Access Plan and GANO noise limits are provided in Tables 3 and 4, respectively. It is important to remember that these increases do not represent an increase in the noise levels that will occur in the community. Rather, these increases in the noise limits are necessary to account for new microphones that are more sensitive than the old microphones. As discussed in detail above, these modifications are therefore necessary to maintain parity with the existing noise compliance limits at the Airport. Table 3: Recommended Adjustments, in db, To The Phase 2 Access Plan SENEL Noise Limits Site Increase in Class A Limit New Class A Limit Increase in Class E Limit New Class E Limit 1S S S S S S S Page 20 of 33

21 Table 4: Recommended Adjustments, in db, to the General Aviation Noise Ordinance Site Increase in Daytime Limit New Daytime Limit Increase in Curfew Hours Limit New Curfew Hours Limit 1S S S S NA NA S NA NA S NA NA S NA NA N NA NA N NA NA N NA NA Page 21 of 33

22 Appendix 1 Pistonphone Calibrator Certificates and Memo on Pistonphone Cross-check 19 Page 22 of 33

23 20 Page 23 of 33

24 21 Page 24 of 33

25 MEMO SW Birch Street Suite 250 Newport Beach, CA April 12, 2015 P: F: E: Mr. Vince Mestre, P.E. Associate Vice President Landrum & Brown Fairchild, Suite 230 Irvine, CA P: E: Subject: Calibrator Cross Check for John Wayne Airport (JWA) Dear Mr. Mestre, As requested, BridgeNet International performed a calibrator cross check on March 10, The calibrators that were compared were the following: 1. Bruel & Kjaer 4228 Pistonphone Serial # Used for the JWA Existing System 2. Bruel & Kjaer 4228 Pistonphone Serial # Used for the JWA New System The resulting calibration difference was 0.02 and therefore was considered to be less than significant. Sincerely, BridgeNet International Justin W. Cook, INCE, LEED GA Vice President 22 Page 25 of 33

26 Appendix 2 Statistics and Measurement Uncertainty 23 Page 26 of 33

27 The measurement of any quantity whether it be weight, length, speed, or sound pressure level is subject to measurement uncertainty. In lay terms, measurement uncertainty is known as accuracy. Because accuracy is poorly defined, international standards bodies have chosen to use the term uncertainty to reflect a very specific meaning. For example, a common definition of accuracy is the quality or state of being correct or precise ; however, it is not very clear how you measure correctness. Precision refers to the resolution of the measurement, for example, in the case of measuring length whether the resolution is tenths of an inch, hundredths of an inch, thousandths of an inch, etc. Quantifying measurement uncertainty is important because it provides an estimate of the probability that a measurement is correct. Simply put, when a measurement uncertainty is stated according to accepted practice, the results are stated in terms of the average value and the range of uncertainty. For example, in the case of noise measurements, a result may be stated as an expected result of 90 decibels plus or minus 2 decibels. This means that there is a 95% probability that the true, or correct, result lies between 88 and 92 decibels. The method of estimating uncertainty is quite complex and will not be discussed in detail here. The topic is addressed thoroughly in two ISO documents 8, 9 and an SAE document 10. The statistics used to compute the uncertainty of measurement and the resulting uncertainty of measurement are shown in Table 5. For example, the first line of Table 5 presents the results for the A306 aircraft (Airbus A300 flown by FedEx) at site 101 (the Table is numbered according to the temporary names of the new sites 101, 102, 103 and 108 so as to not confuse these data from the currently used official sites of 1S, 2S, 3S and 8N). The following are the data from the first line: Site: 101, collocated with 1S, the existing system arithmetic average SENEL was 95.9 db with a standard deviation of 1.8 db and an uncertainty of plus or minus 0.5 db. And the new system arithmetic average was 96.4 db with a standard deviation of 1.8 db and an uncertainty of 0.6 db. The total count of operations was 42 and the average difference was 0.5 db with a standard deviation of 0.1 db and a 8 International Standards Organization (ISO) 20906, Unattended Monitoring of Aircraft Sound in the Vicinity of Airports, Annex B, Uncertainty of Reported Data. 9 International Standards Organization (ISO), Guide 98-3, Uncertainty of Measurement, Part 3, Guide to the Uncertainty of Measurement (Gum: 1995). 10 Society of Automotive Engineers (SAE), Aerospace Recommended Practice, ARP 4721, "Monitoring Noise From Aircraft Operations In The Vicinity of Airports." 24 Page 27 of 33

28 measurement uncertainty of 0.04 db. This means the true average difference has a 95 percent probability of lying between 0.46 and 0.54 db. Note that Table 5 uses arithmetic averages for the purposes of computing uncertainty (per ISO 20906, Annex B) while the actual SENEL averages and resulting differences were based on computing an energy average per the terms of the Phase 2 Access Plan. Table 5: Summary of Estimations of Measurement Uncertainty Old-Average- SENEL Old-Std- Dev +5Uncertainty New-Average- SENEL New-Std- Dev +5Uncertainty Count Average- Difference Std-Dev +5Uncertainty Site Aircraft 101 A A30B A A A B B B B CRJ CRJ A A30B A A A B B B B CRJ CRJ A A30B A A A B B B B CRJ CRJ A A30B A A A B B B B CRJ CRJ Page 28 of 33

29 Appendix 3 Photographs of Monitor Sites With Side-by-side Microphones 26 Page 29 of 33

30 Attachment A Site 1S Page 30 of 33

31 Attachment A Site 2S Page 31 of 33

32 Attachment A Site 3S Page 32 of 33

33 Attachment A Site 8N Page 33 of 33