Noise 101

There are currently 23 noise monitoring terminals (NMTs) surrounding San Diego International Airport (SAN) in communities ranging from Golden Hill, Uptown, Loma Portal, Point Loma, Ocean Beach, and Mission Beach. These sites, which are acoustic microphones mounted on tall poles, measure noise and transmit the data, twenty-four hours a day, to a computerized noise monitoring and flight tracking system located at the Airport. The data is evaluated and compiled to meet State requirements, and periodic reports are submitted to the County of San Diego and the State of California, Division of Aeronautics. The system also helps staff monitor noise levels and aircraft flight tracks. Additionally, stored information is used to confirm departure curfew violations and to respond to aircraft noise complaints from community members. Finally, downloaded information from the 23 NMTs is used to develop a noise contour map that defines the area of noise-impacted communities.

SAN uses Airport Noise and Operations Monitoring System (ANOMS), a highly flexible and fully integrated computerized aircraft noise monitoring and flight tracking system. ANOMS allows staff to manage SAN’s noise compatibility program to meet community and state requirements, and is one of the most sophisticated aircraft noise monitoring systems in the world. Visitors from as far away as Australia, Denmark, France, and Spain have visited to acquaint themselves with the system and its capabilities. Demonstrations of the ANOMS are offered, by appointment, to interested parties. To schedule a demonstration, call (619) 400-2660.

The decibel (dB) a metric that is commonly used in acoustics as a unit of sound pressure level. Sound pressure level is a measure of the sound pressure of a given noise source relative to a standard reference value, where the reference value is set as the typical threshold of perception of an average human. Decibels are computed logarithmically. Airport Noise Mitigation’s NMTs use A-weighting. In hearing individual aircraft (a single event), a change of 3 dB is usually discernable by most people, a change of a single event of 10 dB is significant. Aircraft noise in the vicinity of SAN is made up of many events, including aircraft takeoffs, landings, overflights, and ground noise (the noise generated by aircraft on taxiways and gate areas). These are commonly referred to as single event noises and are described by sound exposure levels (SELs). The overall airport noise environment is described and defined by the Community Noise Equivalent Level (CNEL) metric. The CNEL is a 24-hour noise dose average (on an energy basis) of all SELs recorded.

A noise contour map Is a map depicting the noise levels around SDIA. Noise Mitigation produces noise contour maps using the CNEL metric. The noise contours are produced through the use of the FAA’s computer model called the Aviation Environmental Design Tool (AEDT). Airport Noise Mitigation generates four quarterly noise contour maps identifying the 65 dB CNEL contour (State and Federally defined Noise Impact Area (NIA)). In addition, a calendar year multi-contour (60 to 80 CNEL) is produced. Airport Noise then uses its GIS to produce the map and run the NIA calculations.

Below is a sample copy of an Annual contour map.

The current production of civilian aircraft is markedly quieter than the older technology aircraft.  Dramatic reductions in engine noise have occurred since the early 1980s.  However, the reduction in noise with each new generation of engine is not as dramatic as previous generations.  Small evolutionary changes may be occurring, but the technological noise reduction achieved through higher engine bypass ratios has a limit, and that limit is being approached.  This information does not imply that reductions achieved will not be maintained, only that the continued improvements may be less dramatic.  A new Boeing 787 has approximately one-tenth the noise “signature” on departure as a Boeing 727-200, yet it carries more than twice the number of passengers.  Because aircraft have operating lives of 20 or more years, it takes decades for airline fleets to catch up to the latest and quietest technology.  Absent any compelling incentive or regulatory requirements to retire older aircraft, airlines naturally expect to extend the usefulness of their capital investments for as long as possible.

During nighttime hours, ambient (background) noise levels are generally low; therefore, noise events may be judged louder because the low ambient noise levels are used as a base for comparison.  In addition, more noise events may be audible at low ambient noise levels.  In comparison, during the daytime hours, ambient noise levels are likely to be higher because normal activity masks some noise events.  To accommodate for these nighttime noise impacts the CNEL includes a 10 dB penalty from the hours 10:00 p.m. to 7:00 a.m. and a 5 dB penalty from 7:00 p.m. until 10:00 p.m.  This is done to accommodate for the fact that human hearing perceives these noise events to be louder, even when they are not.

An “early turn” is a jet aircraft that deviates from the standard departing procedures.  Airport staff can use the ANOMS system to determine if departing aircraft is an “early turn”.

SAN has only one runway, requiring aircraft to depart to the west, or the east, depending on the surface wind direction. Prevailing westerly winds dictate that aircraft arrive using Runway 27 (over Balboa Park) approximately 97% of the time. This requires aircraft to depart westerly over Ocean Beach. Easterly arrivals and departures (over Balboa Park) occur less than 3% of the time (usually during periods of Santa Ana type winds or inclement weather). Air carrier aircraft departing SAN to the west are normally assigned by FAA ATC personnel one of two Standard Instrument Departure (SID) procedures depending on their departure destination. For example, for Runway 27 departures, aircraft departing to Los Angeles, San Francisco, and airports west and northwest of San Diego, aircraft are usually assigned an initial departure procedure to make a “right turn” of approximately 15 degrees after takeoff. Aircraft destined for Phoenix, Denver, Dallas, and airports south and east of San Diego are usually assigned an initial departure procedure to go “straight out”. The number of aircraft using each procedure varies depending on airline schedules and FAA air traffic controllers’ discretions, but historically has often been close to a 50/50 split. While there are navigational aids assisting the pilots in maintaining their flight routes, winds can still cause shifts in the departure routes. While winds are always going to be a factor in the flight path of aircraft, the use of GPS tightens corridors where aircraft will fly.

During Contra-Flow operations, aircraft arrive from the west, and depart to the west on a reciprocal heading, “head-to-head”. This procedure is utilized when some aircraft’s performance and/or weight do not allow them to depart to the east. Once airborne, departing aircraft are vectored south (over south Pt. Loma) or north (over North Mission Beach) to clear the airspace for arrivals into SAN. These operations occur rarely and significantly reduce the operational capacity of the airport when they occur.

A missed approach, also commonly referred to as a “go-around”, occurs when an aircraft cannot complete their landing and are required to go around attempting to land again.  Reasons aircraft execute a missed approach are listed below.  Please note that this list is not inclusive.

• A departing aircraft is exiting the airspace/runway slower than an arriving aircraft is entering the airspace/runway.  In an effort to ensure safe separation of each aircraft, a missed approach is executed.
• A change in weather conditions has reduced minimums to the point that the pilot must terminate the descent and executes a missed approach.
• A pilot is approaching the field at a speed or altitude that would not permit the aircraft to touch down at a reasonable distance past the displaced threshold (landing line) and still have enough runway remaining for braking and/or reverse thrust.
• Operations have been halted because foreign object debris (FOD) has been spotted on the runway and must be removed prior to resuming operations.
• Slow flow of departures and/or arrivals.

Flight path procedures are dictated by the FAA, taking into account considerations of operational, safety, and air traffic control procedures.  The airport operator has no authority to regulate flight paths.  Therefore, although an airport may advocate for certain noise abatement flight paths to reduce noise, the request must be investigated for its impact on the National Airspace System Plan (NASP).  Any new flight path procedures are implemented at the discretion of individual airlines after approval by the FAA.

Aircraft altitude is generally determined by distance from the landing or takeoff runway. The closer the aircraft is to the runway, the lower the altitude. SAN arrivals normally descend at a fixed angle of approximately three and one half (3.5) degrees as they approach for landing. The angle of ascent on departures is a function of aircraft type, weight, air temperature, and wind speed. Our eyes can actually deceive us when comparing aircraft at the same heights but of differing sizes.

Each air carrier operating at SAN has discretion to designate a standard Noise Abatement Departure Profile (NADP) for each aircraft type they operate in a manner consistent with the procedures specified in FAA Advisory Circular 91-53. There are two NADPs, the “Close-In” and “Distant”. The appropriate NADP depends upon many factors including, but not limited to, aircraft type, weight, and passenger load. The usefulness of an NADP at any particular airport also depends on where noise affected communities are located relative to the runway and normal flight tracks. At some airports, some NADP’s would actually be counterproductive and would increase rather than decrease residential noise exposure.

A preferential runway (PR) system is a local traffic control procedure that identifies a specific runway for use when specific conditions are present. It is generally defined by a set of operational rules and parameters affecting or limiting runway selection options under defined weather and/or operational circumstances, and these programs are generally implemented by agreements between the FAA, airport operators, and airport users, and are typically developed to support noise abatement or noise control objectives. SAN does not have a PR because there is only one runway surface and a westerly prevailing wind 97% of the time or greater. Another type of preferential runway system is called a nighttime preferential runway system (NPR). A NPR is most commonly used to minimize the effect of aircraft noise on residential communities during nighttime and early morning hours. SAN’s prevailing westerly wind and an Instrument Landing System (ILS) to only one of the runways (Runway 09) make an NPR infeasible.

An operation consists of a takeoff, landing, or approach (aircraft sometime use the SAN approach and land at NAS North Island). For example, an aircraft arriving at SAN and then departing some time later is counted as two operations. SAN had over 209,500 operations in 2017, or an average of 280 daily departures and 280 daily arrivals.

By law, the FAA has the sole authority to manage the Air Traffic Control (ATC) system and the navigable airspace in the United States; therefore, the Airport Authority cannot restrict access to “noisier” aircraft or dictate departure routes. At SAN and all commercial airports, from the time an aircraft departs the terminal and enters the taxiway and runway system, and throughout its flight to, and arrival at the gate of the destination airport, the aircraft moves only by instruction and permission of the FAA, and pursuant to the direction of FAA (not airport) personnel.

The Federal Aviation Administration (FAA) provides noise classifications on various types of aircraft under the standards established in Advisory Circular (AC) 36-4D, “Noise Standards: Aircraft Type and Airworthiness Certification” (also referred to as “Part 36”). Aircraft may be certificated as Stage 1, Stage 2, or Stage 3 based on its noise level, weight, and number of engines. Stage 1 aircraft, the oldest and noisiest aircraft (e.g., B707) are no longer permitted to operate in the United States. Stage 2 aircraft include aircraft models such as the B737-200, B727, and DC-9 aircraft. Stage 2 aircraft have been phased out of the United States’ commercial air carrier fleet as of January 1, 2000. Stage 3 aircraft are the newer, generally quieter aircraft (e.g., B737-300, B757, B767, A320 and MD-80/90 aircraft, etc.). Stage 3 aircraft may also include aircraft that were Stage 2 when manufactured, but have since been fitted with "hush-kits" or have been re-engined and re-certified to meet the Stage 3 noise standards. Although aircraft meeting Stage 3 standards are noticeably quieter than many of the older aircraft, the regulations make no determination that such aircraft are acceptably quiet for operation at any given airport. Since aviation is a global resource, noise level certification is adopted through the International Civil Aviation Organization (ICAO), which the FAA is the U.S. representative legislative body. The FAA is working on integrating the ICAO adopted Stage 4 standard, the ICAO adopted Stage 3 standard for helicopters, and the U.S. adopted phase-out of all remaining Stage 2 aircraft operations (by December 31, 2015).

The California Airport Noise Standards (California Code of Regulations, Title 21, Section 5000 et seq.) “Title 21”. Title 21 provides noise standards governing the operating of an airport within the State. Among many things, Title 21 states that the basis for the acceptable level of aircraft noise for persons living in the vicinity of airports is a CNEL of 65 dB. In addition, Title 21 states that no proprietor of a “noise problem" airport shall operate an airport with a Noise Impact Area (NIA) of 65 dB CNEL unless the operator has applied for and received a Variance from the California Department of Transportation (CALTRANS), Division of Aeronautics (Title 21 Section 5012). SDIA is one of ten California airports subject to the “noise problem airport” requirements. These regulations establish 65 dB CNEL as a NIA within which there shall be no incompatible land uses. SDIA has received 12 such Variances to operate since the late 1970s.

Airport operating restrictions are generally regulatory restrictions which, for noise control or other environmental reasons: (1) limit the type of aircraft which may use the airport; (2) limit the time of day which certain aircraft can use the airport; or (3) limit the number of aircraft which can use the airport during a defined time period. Historically, this has been a complex legal area where the Federal government (principally the Federal Aviation Administration) and the local airport proprietor have had shared regulatory authority. State and local governments that are not airport proprietors, however, have generally been held by the courts not to have any regulatory authority over airport or aircraft operations for noise control purposes because of the preemptive effect of the "pervasive" scheme of federal regulation over such matters.

Although airport proprietors historically had some discretion to control and regulate the use of its airport for noise control and other limited purposes, that discretion has always been subject to substantial Federal oversight and influence by a variety of legal means, including the airport proprietor's obligations to the FAA under standard "grant assurances" given to the federal government under federal legislation dating back to 1946. In 1990, the Congress significantly limited the scope of the local airport proprietor's regulatory discretion for noise control purposes by adopting the Airport Noise and Capacity Act of 1990 (ANCA). FAA has subsequently adopted regulations implementing ANCA under Part 161 of the Federal Aviation Regulations (FAR) (14 CFR Section 161.1). The practical effect of ANCA and implementing legislation (Part 161) is to make traditional aircraft operation regulations by local airport proprietors infeasible without the concurrence of the air carriers or other operators affected by the restriction. To implement the Airport Noise and Capacity Act (ANCA), the FAA amended FAR Part 91 and issued a new FAR Part 161. FAR Part 91 addresses the phase-out of large Stage 2 aircraft and the phase-in of Stage 3 aircraft. Part 161 establishes a stringent review and approval process governing the implementation of local airport use or access restrictions by airport proprietors.

In those cases where aircraft noise, noise abatement, and land use compatibility are issues of special concern, a study may be conducted following the guidelines set forth in FAR Part 150. Planning guidelines for conducting Part 150 studies are described in FAA Advisory Circular 150/5020-1, Noise Control and Compatibility Planning for Airports. A Part 150 Study may also be conducted as part of an Airport Master Plan. The study develops an inventory and five year forecast of aircraft noise, capacity issues and land use considerations. If potential conflicts are determined to exist, alternative noise abatement strategies may be developed and evaluated. If noise abatement strategies that may result in airport restrictions are pursued, the Part 150 Study must also meet the requirements of FAR Part 161, which requires that potential restrictions to airport or aircraft operations undergo an extensive economic impact study and receive FAA review and approval. For info on the SDIA Part 150, click here.

The first part of the Part 161 regulations address any potential noise or access restriction on Stage 3 aircraft which results from an agreement between an airport proprietor and aircraft operators.  The regulations set forth the procedures which must be followed before an airport proprietor and aircraft operators can agree upon a noise or access restriction, including: (1) notice requirements to inform interested parties and those likely to be affected by the outcome of an agreement; (2) provisions to protect and limit the rights of aircraft operators not currently using the airport; (3) requirements for implementing an agreement; (4) procedures for terminating an agreement; (5) provisions to ensure that relevant information is available for public review; and (6) limitations on FAA review of such agreements.  Although the FAA has constantly stated that it encourages airport proprietors and aircraft operators to voluntarily agree on noise and access restrictions, the procedures for entering into an agreement are cumbersome.  Particularly at large air carrier airports, it may be difficult to achieve unanimity, not only from existing affected operators, but also from potential new entrant operators.  Since implemented in 1990, there has never been a Part 161 Study accepted by the FAA.

Regularly published noise reports may be downloaded from the “Quarterly Noise Reports” section of this website or through the Authority Clerk’s Office. For other official noise records, you can submit a Public Records Request.

“The Curfew” is a Time of Day Restriction that limits nighttime aircraft departures.  Departures are prohibited from 11:30 p.m. until 6:30 a.m. the following morning. Aircraft that depart during these hours are subject to fines.  For Helicopters, the departure restriction is from 10:00 p.m. to 7:00 a.m.

Curfew violations are reviewed bi-monthly and base fines between $2,000 and $10,000 can be imposed.  For repeat offenders, the base fine is multiplied by the number of fined violations in the previous six months.

SAN has had a noise departure “curfew” since 1976, and is now formally known as the Airport Use Regulations (AURs) and have been adopted as SDCRAA Code 9.40. The AURs established restrictions on operations at SAN by certain types of aircraft, and prohibit departures by any aircraft during certain times of day, except for Lifeguard/mercy flights. Stage 3 aircraft may depart SAN between 6:30 a.m. and 11:30 p.m. Stage 2 aircraft may only depart between 7:00 a.m. and 10:00 p.m. Arrivals for all aircraft types are permitted twenty-four hours a day. The primary operators at SAN during the early morning hours are cargo carriers, whose business model revolves around early morning delivery. The Airport Noise and Capacity Act (ANCA) passed by Congress in 1990 severely restricted the airport proprietor’s ability to impose new restrictions on operations. Pre-existing regulations (i.e., before November 1990) were unilaterally exempted and are not subject to ANCA unless they are suspended or changed to further increase the exempted restrictions.

The following is an alphabetic list with definitions of terms/acronyms used in the FAQs with which you may not be familiar.

AC - Advisory Circular: Information letters issued by FAA to inform the public in a systematic way of non-regulatory material.

ANCA - Airport Noise and Capacity Act: This 1990 Federal Law established a "national policy on aviation noise". Its main feature is to require that by the year 2000 all jet aircraft used in commercial service at civilian airports be Stage-3 aircraft. Found under U.S. Code Title 49, Subtitle VII, Part B, Chapter 475, Subchapter II – National Aviation Noise Policy.

AEDT – Aviation Environmental Design Tool: FAA’s newest standard tool for determining the predicted noise impact in the vicinity of airports. AEDT uses flight track information, aircraft fleet mix, standard and user defined aircraft profiles, and other inputs to produce noise exposure contours. The AEDT also allows for modeling aircraft on the ground, something the INM could not do.

ANOMS – Airport Noise and Operations Monitoring System: SAN’s computerized noise monitoring and flight tracking system. The ANOMS software is created by Brüel & Kjær.

ASDI – Aircraft Situation Display to Industry. ASDI is a data stream service made available by the FAA. The stream consists of data elements which show the position and flight pan data of all aircraft in the U.S. This data includes the location, altitude, airspeed, destination, and ETA, and tail number or identifier of the aircraft. For more info see: http://en.wikipedia.org/wiki/ASDI.

ATC - Air Traffic Control: that segment of the Federal Aviation Administration (FAA) responsible for controlling aircraft movement on the ground and in the air. For more info see: http://en.wikipedia.org/wiki/Air_traffic_control.

ATCT – Air Traffic Control Tower: FAA facility established at most larger airports to provide for a safe, orderly and expeditious flow of aircraft.

AURs – Airport Use Regulations: SAN’s noise regulations or “Curfew”. Codified under SDCRAA Code 9.40.

A-weighting – A-weighting is a noise curve defined by international standards. A-weighting is applied to measured noises in an effort to account for how humans perceive noise.

http://en.wikipedia.org/wiki/A-weighting

Beacon Code – See Transponder Code

CA PUC – California Public Utilities Commission: A California agency that oversees and regulates, among other things, all public use airports under the California Department of Transportation, Division of Aeronautics.

Class B Airspace – A FAA defined term where an aircraft operation is subject to ATC clearance and separated by ATC.

For more information see; http://en.wikipedia.org/wiki/Airspace_classes

CNEL – Community Noise Equivalent Level: The noise metric used to measure cumulative aircraft noise impact in California

"Contra-Flow" Operations: A local air traffic control procedure used at SAN during inclement weather conditions, which require arrival and departure operations in the same direction.

CVRP – Curfew Violation Review Panel: SAN’s review panel for suspected violations of the Time of Day (Curfew) noise restrictions.

dB (Decibel): the decibel is a logarithmic unit (metric) used to express the ratio between two values of a physical quantity, often power or intensity. In acoustics, the decibel is used as a unit of sound pressure level. Sound pressure level is a measure of the sound pressure of a given noise source relative to a standard reference value, where the reference value is set as typical threshold of perception of an average human.

http://en.wikipedia.org/wiki/Decibel

FAA – Federal Aviation Administration: the national aviation authority of the United States of America. For more info visit:

www.faa.gov http://en.wikipedia.org/wiki/FAA

FAA TRACON – Terminal Radar Approach Control: An FAA facility that provides advisory service to aircraft during the departure and approach phases of flight.

FAR – Federal Aviation Regulations: Implementing legislation for federal laws pertaining to aviation activities.

GIS – Geographic Information System: SAN’s computerized geographic mapping and analysis system. The system currently uses ESRI’s ArcGIS.

Grant Assurance: Specific obligations and certification required of airports to meet requirements of Federal grants for airport planning and development projects.

ICAO – International Civil Aviation Organization: is a United Nations (UN) specialized agency created in 1944 upon the signing of the Convention on International Civil Aviation (the “Chicago Convention”). ICAO works to develop international standards and best practices.

IFR – Instrument Flight Rules: rules and regulations established by the FAA to govern flight under conditions in which flight by aircraft outside visual reference is not safe (i.e. not VFR).

INM – Integrated Noise Model: FAA’s standard tool for determining the predicted noise impact in the vicinity of airports. INM uses flight track information, aircraft fleet mix, & standard and user defined aircraft profiles to produce noise exposure contours.

Missed Approach: A climbing maneuver accomplished by a pilot of an airplane when a landing cannot be accomplished safely.

NADP – Noise Abatement Departure Profile: A type of departure procedure where the end result is to reduce the noise on a jet aircraft’s departure. The FAA regulates NADPs under AC 91-53A.

NASP – National Airspace System Plan: A management description of the FAA system framework that will allow for future growth in aircraft operations in a safe and expeditious manner.

NIA – Noise Impact Area: under Title 21, the noise impact area is defined as the area within the noise impact boundary (65 dB CNEL noise contour) that is composed of incompatible land uses.

QHP – Quieter Home Program: SAN’s Residential Sound Attenuation Program (RSAP).

PASSUR – PASsive SUrveillance Radar. The means by which Noise Mitigation tracks aircraft.

http://www.passur.com/

Part 36 – FAA’s Noise Standards: Aircraft Type and Airworthiness Certification. (Currently Advisory Circular (AC) 36-4C).

Part 150 – FAA’s Airport Noise and Compatibility Planning program. (Title 14 Part 150).

Part 161 – FAA’s Airport Noise and Access Restrictions program. (Title 14 Part 161).

PR/NPR – Preferred Runway/Night Preferred Runway: A local air traffic control procedure recommending use of a certain runway for arrivals and/or departures when specific conditions exist (i.e., for noise abatement purposes).

Radar – Acronym for RAdio Detection And Ranging. Radar is an object detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. For more info, visit http://en.wikipedia.org/wiki/Radar.

RMS – Remote Monitoring Site/Station: Another name for an RMT.

RMT - Remote Monitoring Terminal: the sites in the community where permanent microphones are placed to measure aircraft noise and define the areas most adversely affected by aircraft operations.

SDCRAA – San Diego County Regional Airport Authority: the policy body for SAN since January 1, 2003. Prior to this date, the San Diego Unified Port District provided policy guidance for the airport. www.san.org

SAN - San Diego International Airport (Lindbergh Field)

SEL – Sound Exposure Level: is a common measure of cumulative noise exposure for a single noise event. The SEL is a summation of the A-weighted sound energy over the duration of a noise event, where duration is defined as the time when the sound level first exceeds a threshold level (normally just above the background or ambient noise).

SID – Standard Instrument Departures: Published Air Traffic Control procedures an aircraft must adhere to immediately after takeoff. Because of surrounding terrain or noise abatement restrictions, these procedures detail any turns or speed and altitude restrictions pilots must comply with unless amended or superseded by ATC.

Stage 1/2/3/4 - Certification of aircraft according to their specific noise levels under Part 36 – Stage 4 is the latest technology, thus the quietest aircraft in the fleet.

Title 21 – California Code of Regulations, Title 21, the “Airport Noise Standards”. CA State Regulations (CA PUC, Title 21, Subchapter 6) governing the operation of aircraft and aircraft engines for all airports operating under a valid permit issued by the California Department of Transportation (CalTrans).

Transponder – A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders that identify themselves on FAA Air Traffic Control Radar. Transponder codes, also called Beacon codes, are 4-digit octal numbers (go from 0 to 7), therefore the lowest code is 0000 and the highest is 7777. For more info, see:

http://en.wikipedia.org/wiki/Transponder_(aviation)#Secondary_Surveillance_Radar

VFR – Visual Flight Rules: a set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow pilots to see where the aircraft is going.