Noise

This chapter provides background discussion on sound; noise environmental sound descriptors; noise metrics; noise analysis; and the noise associated with aircraft operations, including that generated by inflight operations and maintenance run-up operations.

Basics:

What is sound?

Basically sound is vibration created by a moving object. that can be an air molecul. if an air particle hits another air particle you have a crash noise. moving an object like a helicopter through airspace would push particles and create a so called wave. A wave is a dynamic source of power leading from initator out into space. the power reduces over distance. as residing air is pressed in front of a flying object the movement happens sideways and back. This wave splits dynamics into red respectively blue waves. objects closing are red, objects going away are blue.

The very initial type of molekul motion is when energy is added. For example heat. Heat get molecules to dance or vibrate. Cooling air would calm down vibration.

To get a sound you need energy, a force, an object as transmitter and a receiver to interprete the vibration.

And that works with simple math: the initial object hits air molecules which themselves hit the next couple of molecules in the direction of force. The number of transmitting object rises, and the initial power coming from the first object push will eventually become weaker, as its engergy transmits and splits into any of the resisting objects in the wave. Whatever remains of vibrating molecules over a distance will arrive in the ear of the listener. The middle ear bone starts taking the energy of the wave and translates it into vibration. This vibration is equal a signal, and it goes to the brain part responsible to interprete the signal as what we call "hearing".

Any material can transport vibration. Water, Air, Soil, Concrete. The higher the Density of the material the better vibrations can reach out. It all happens on molekule size level. and can end in huge oversized explosive pressure wave. Unvisible, but extremely powerful. Drop a bomb and you know.

Why are there different sounds?

The shape of the wave described equals the character of the sound. Yes, you could 3d-model sound waves and get it translated into a sound making machine.

Elements of sound:

source, power, distance, wave shape, frequency, wave length, temperature/density, resisting molekules.

...

4.1 Aircraft Sound Sources

The main sources of sound at air installations are generally related to in-flight operations, pre-flight and maintenance run-up operations. Computer models are used to develop noise contours for land use planning purposes based on information about these operations, based upon the following factors: • Type of operation (e.g. arrival, departure, pattern) • Number of operations per day • Time of operation • Flight track • Aircraft power settings, speeds, and altitudes • Number and duration of maintenance run-ups • Environmental data (temperature and humidity) • Topographical features of the area • Ground surface characteristics

4.2 What is Noise?

Noise is unwanted sound. Sound is a physical phenomenon consisting of minute vibrations that travel through a medium, such as air, and are sensed by the ear. Whether that sound is interpreted as pleasant (e.g., music) or unpleasant (e.g., jackhammers) depends largely on the listener's current activity, past experience, and attitude toward the source of that sound. Sound is all around us; sound becomes noise when it interferes with normal activities such as sleep and conversation. Aircraft noise is of concern to many in communities surrounding airports. The impact of aircraft noise is also a factor in the planning of future land use near air facilities. Because the noise from these operations impacts surrounding land use, we have created a 3D-noise zone and sphere model and provide associated recommendations regarding compatible usage in X-Plane.

4.3 Characteristics of Sound

The measurement and human perception of sound involves three basic physical characteristics—intensity, frequency, and duration. Intensity is a measure of the acoustic energy of the sound vibrations and is expressed in terms of sound pressure. The higher the sound pressure, the more energy carried by the sound and the louder the perception of that sound. Frequency is the number of times per second the air vibrates or oscillates. Low-frequency sounds are characterized as rumbles or roars, while sirens or screeches typify high-frequency sounds. Duration is the length of time the sound can be detected. A logarithmic unit known as decibel (dB) is used to represent the intensity of sound. Such a representation is called a sound level. The decibel is an event measurement as opposed to the DNL which is a day and night average level. A sound level of 10 dB is approximately the threshold of human hearing and is barely audible under extremely quiet conditions. Normal speech has a sound level of approximately 60 dB. Sound levels above 120 dB begin to be felt inside the human ear as discomfort and above 140 dB as pain. Sounds levels of typical noise sources and environments are shown in Figure 4-1. Because of the logarithmic nature of the decibel unit, sound levels cannot be arithmetically added or subtracted. Therefore, the total sound level produced by two sounds of different levels is usually slightly higher than the higher of the two. If two sounds of equal intensity are added, the sound level increases by 3 dB. For example:

60.0 dB + 70.0 dB = 70.4 dB;

60 dB + 60 dB = 63 dB.

For a noise event, a change of 3 dB of event noise is the smallest change detected by the average human ear. An increase of about 10 dB is usually perceived as a doubling of loudness. This applies to sounds of all volumes. A small change in dB generally will not be noticeable. As the change in dB increases, the individual perception is greater, as shown in Table 4-1 below

Table 4-1 Subjective Responses to Changes in A-weighted Decibels (dBA)

Change Change in Perceived Loudness

1 dB Requires close attention to notice

3 dB Barely perceptible

5 dB Quite noticeable

10 dB Dramatic, twice or half as loud

20 dB Striking, fourfold change

Source: Wyle Laboratories 2004.

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Figure 4-1 Sound Levels of Typical Sources and Environments

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4.3.1 Environmental Sound Descriptor The sound environment around an air installation is typically described using a measure of cumulative exposure that results from all aircraft operations. The metric used to account for this is day-night average sound level (DNL) and is the standard noise metric used by the US Department of Housing and Urban Development, FAA, U.S. Environmental Protection Agency, and DOD. Studies of community response to numerous types of environmental noise show that DNL correlates well with the level of annoyance. A more detailed description of DNL follows: • In general, DNL can be thought of as an accumulation of all of the sound produced by individual events that occur throughout a 24-hour period. The sound of each event is accounted for by an integration of the changing sound level over time. These integrated sound levels for individual events are called sound exposure levels (SELs). The logarithmic accumulation of the SELs from all operations during a 24-hour period determines the DNL for the day at that location. • DNL also takes into account the time of day the events occur. The measure recognizes that events during nighttime hours may be more intrusive, and therefore more annoying, than the same events during daytime hours, when background sound levels are higher. To account for this additional annoyance, a penalty of 10 dB is added to each event that takes place during “acoustic” nighttime hours, defined as 2200 to 0700 hours the next day. • DNL values around an air installation are presented not just for a single specific 24-hour period, but rather for an annual average day. DNL averaging is done to obtain a stable representation of the noise environment free of variations in day-to-day operations or between weekdays and weekends as well as from fluctuations in wind directions, runway use, temperature, aircraft performance, and total airfield operations (any one of which can significantly influence noise exposure levels from one day to the next). 4.3.2 Individual Response to Sound Levels Individual response to sound levels is influenced by many factors, including the following: • Activity the individual is engaged in at the time of the event • General sensitivity to sound • Time of day • Length of time an individual is exposed to a sound • Predictability of sound • Average temperature/inversions/other weather phenomena Various scientific studies and social surveys have found a high correlation between the percentages of groups of people in communities highly annoyed and increases in the level of average sound exposure measured in DNL. This correlation is shown in Figure 4-2 from two studies. Such aircraft noise annoyance correlation was originally developed in the 1970s (dashed line in Figure 4-2) and was reaffirmed by the more recent study curve (solid line in Figure 4-2). The curve remains the best available method to estimate the community reaction to aircraft sound levels. Most people are exposed to sound levels of 50-55 DNL or higher on a daily basis. Research has indicated that about 87 percent of the population is not highly annoyed by outdoor sound levels below 65 dB DNL (Federal Interagency Committee on Urban Noise 1980).

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Source: Shultz 1978 and Finegold, et al 1994; as taken from Wyle Laboratories, Draft Wyle Report 08-13 Aircraft Noise Study for MCBH 2008. Figure 4-2 Influences of Sound Levels on Annoyance Appendix B provides additional information on sound and noise

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4.4 Noise Concerns and Noise Abatement Procedures 4.4.1 Noise Concerns MCB Hawaii engages in a variety of training exercises and real-world military operations which sometimes generate aircraft and weapon noise. This includes aircraft training at MCAS Kaneohe Bay and surrounding airspace and range operations at Puuloa Training Facility and Marine Corps Training Area Bellows. Residents near MCB Hawaii properties (e.g., Kaneohe, Kailua, Waimanalo, Kahaluu, and Ewa) identify military noise as a community concern. MCB Hawaii’s leadership regularly meets with community leadership, including state legislators and local city officials, to discuss relevant issues. Because the base acknowledges its operations affect surrounding communities, it evaluated Standard Operating Procedures to ensure there is a proper balance between training Marines and sailors, as required by the Department of Defense, and considering impact to residential areas. For instance, engine testing maintenance hours and aircraft flight paths were adjusted in order to reduce noise. While it is normal and legal under federal law for aircraft to fly over land, MCB Hawaii established more specific course rules in order to outline a safe and expeditious pathway for tenant and transient aircraft to depart and arrive at the airfield. MCB Hawaii course rules are designed to keep aircraft over water and away from populated areas. However, pilots will occasionally fly over land or deviate from the local course rules to maintain safe flight operations. MCB Hawaii pilots are among the most professional and best-trained in the world, and they always operate in a safe and efficient manner while striving for noise abatement. Residents should be aware noise will vary due to real-world missions, overseas deployments, training requirements, federal funding, maintenance, and weather. Since 2001, marine, sailor and equipment levels at MCB Hawaii have fluctuated due to operations in Afghanistan and Iraq. Currently, MCB Hawaii personnel are participating in the Unit Deployment Program and units rotate to Japan every six months. MCB Hawaii distributes the Aloha Newsletter via email and the base website in order to provide information about upcoming training exercises, community events and other base operations. Residents may call MCB Hawaii’s dedicated noise information line at 808- 257-8832 to sign up for the newsletter. This number is manned during working hours and has voicemail after hours. To file a noise concern, callers should provide their name, the address or general location of where the noise occurred, the time of the incident, and (if applicable) the type of aircraft. The base has also recently launched an online form that allows users to submit their concerns electronically. A link to the form is located on the homepage at www.mcbhawaii.marines.mil. Each call and message is logged for review by commanders and involved units. 4.4.2 Noise Abatement Noise abatement procedures followed by MCB Hawaii are based on Marine Corps Air Flight Operations P3710.1H. These procedures include: • High power engine run-ups are normally restricted to the hours of 0600 to 2200 Monday through Friday, and 0800 to 1800 hours on Saturdays and Sundays. • All station based aircrews are directed to comply with local course rules and deviate only as necessary in the interest of safety or during emergencies. • Aircraft departing Runway 22 shall avoid Coconut Island and populated areas by turning right to a heading of 340 degrees once past Taxiway F. • Fixed-wing Touch and Gos from 2200 to 0600 are discouraged and must be preauthorized case by case by Airfield Operations. • Fort Hase arrivals/departures are only authorized between 0600 and 2200 hours and do not overfly private housing areas. • Helicopters are to avoid beaches by one mile when below 1,500 feet. • Aircraft shall avoid overflying the Nu‘upia Ponds to the south and base residential areas to the north of LZ Boondocker 4.5 Noise Metrics As used in environmental noise analyses, a metric refers to the unit or quantity that measures the effect of noise on the environment. The metric for the noise environment on and in the vicinity of airbases is normally described in terms of the time-average sound level generated by the aircraft operating at the facility. The federal noise metric used for this purpose is the DNL defined in units of dB. DNL has been determined to be a reliable measure of community sensitivity to noise and has become the standard metric used in the United States to quantify noise in aircraft noise studies and associated compatible land use and zoning analysis. Aircraft noise is expressed in terms of A-weighted sound levels. A-weighting is a method of adjusting the frequency content of a sound event to closely resemble the way the average human ear responds to aircraft sound. The A-weighted scale is therefore considered to provide a good indication of the impact of noise produced by aircraft operations. The average of sound over a 24-hour period considers the louder single events. When sound levels of two or more sources are added, the source with the lower sound level is dominated by the source with the higher sound level. The combined sound level is usually only slightly higher than the sound level produced by the louder source. For example, if a single daytime aircraft over-flight measuring 100 dBA for 30 seconds occurs within a 24-hour period in a 50-dBA noise environment, the DNL will be 65.5. If 10 such 30-second aircraft overflights occur in daytime hours in the 24-hour period, the DNL will be 75.4. Therefore, a few maximum sound events occurring during a 24-hour period will have a strong influence on the 24-hour DNL even though lower sound levels from other aircraft between these flights could account for the majority of the flight activity. It is important to note however, that individuals do not "hear" DNL. The DNL contours are intended for land use planning, not to describe what someone hears when a single event occurs. The accumulation of noise computed in this manner provides a quantitative tool for comparing overall noise environments and is useful in developing compatible land use plans and zoning regulations in the airfields’ environs. The DNLs are represented as contours connecting points of equal value, usually in 5- dB increments. The AICUZ footprint, as depicted in Figures 4-3 and 4-4, is defined as contours from 65 dB up to 85dB. The 65dB contour is used to define the AICUZ study area in accordance with the Title 14, Code of Federal Regulations, Section 150.21 – Airport Noise Compatibility Planning, EPA Order 5050.4B., and OPNAVINST 11010.36C/MCO 11010.16. AICUZ Noise Zone 2 (DNL 65-74 dB) is an area of moderate impact where some land use controls are recommended and Noise Zone 3 (DNL 75 dB and above) is the most severely impacted area and the greatest degree of land use controls for noise exposure are recommended. Noise Zone 1 (less than 65 dB DNL), (unshaded area) is an area of low or no impact (although some people in these areas may be annoyed by aircraft overflights) and is included in the AICUZ boundary for informational purposes. These noise zones are shown on Figures 4-3 and 4-4 for the baseline and prospective scenarios, respectively. In Hawaii, the State Department of Transportation uses the 60dB contour for determining compatible land use around commercial airports. This program is parallel to, but does not apply to military airfields which use the AICUZ study and the Federal DNL standard of 65 dB. Therefore, for local planning purposes, this AICUZ study has also depicted DNL contours from 55 dB up to 65 dB that are located outside of the military AICUZ footprint. While the DNL noise descriptor is the most commonly used tool for analyzing noise generated at an air installation and is used as the metric for AICUZ study purposes, the DOD has been developing additional metrics (and analysis techniques) particularly in assessing noise exposure from a noise flight event. These supplemental metrics and analysis tools provide additional noise exposure information such as Sound Exposure Level (SEL) and Maximum Sound Level (Lmax) and they can provide a direct comparison of the relative intrusiveness among single noise events of different intensities and durations of aircraft overflights.

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Figure 4-3 Baseline DNL Contours (dB)

Figure 4-4 Prospective Scenario (2018) DNL Contours (dB)

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The SEL metric is a composite metric that represents both the intensity of a sound and its duration. Individual time-varying noise events (e.g., aircraft overflights) have two main characteristics: a sound level that changes throughout the event and a period of time during which the event is heard. SEL provides a measure of total sound energy of the entire acoustic event, but it does not directly represent the sound level heard at any given time. During an aircraft flyover, SEL captures the total sound energy from the beginning of the acoustic event to the point when the receiver no longer hears the sound. It then condenses that energy into a 1-second period of time and the metric represents the total sound exposure received. The SEL has proven to be a good metric to compare the relative exposure of transient sounds, such as aircraft overflights. The highest A-weighted sound level measured during a single event where the sound level changes value with time (e.g., an aircraft overflight) is called the maximum A-weighted sound level or Lmax. During an aircraft overflight, the noise level starts at the ambient or background noise level, rises to the maximum level as the aircraft flies closest to the observer, and returns to the background level as the aircraft recedes into the distance. Lmax defines the maximum sound level occurring for a fraction of a second. For aircraft noise, the “fraction of a second” over which the maximum level is defined is generally 1/8 second (American National Standards Institute 1988). For sound from aircraft overflights, the SEL is usually greater than the Lmax because an individual overflight takes seconds and the Lmax occurs instantaneously. Lmax can be used to compare aircraft noise levels with respect to speech interference. 4.6 Noise Contours At a minimum, DOD requires that contours be plotted for DNL values of 65, 70, 75, and 80 dB in AICUZ studies. Three general noise exposure zones are defined in the AICUZ Program: areas with a DNL of less than 65 dB; areas with a DNL between 65 dB and 75 dB; and areas with a DNL of 75 dB or greater. These three areas are defined as AICUZ Noise Zones 1, 2, and 3, respectively. 4.6.1 Methodology The Navy periodically conducts noise studies to assess the noise impacts of aircraft operations. As with updates to AICUZ studies, the need to conduct a noise study is generally prompted by a change in aircraft operations — either by the number of operations conducted at the airfield, the number and type of aircraft using the airfield, or the flight paths used for airfield departure/arrival changes. A noise study is also normally conducted as a part of an update to an AICUZ study. The DOD NOISEMAP suite with the Rotorcraft Noise Model (RNM Version 7.357) is the current DOD standard computer model that projects noise levels from both fixed and rotary wing aircraft operations around military airfields and generates noise contour data. NOISEMAP calculates DNL contours resulting from aircraft operations using such variables as power settings, aircraft model and type, maximum sound levels, and duration and flight profiles for a given airfield. Analyses of aircraft noise exposure and compatible land use around an air installation. The flight tracks, as well as pre-flight and maintenance run-up operations, establish the shape of the noise contours. In general, approaches and departures cause the narrow tapering of portions of the contours aligned with the flight tracks, while touch and go operations can determine the general contour size. Noise from pre-flight and maintenance run-up operation locations, if not overshadowed by flight operations, causes generally circular arcs. The noise modeling for this update includes atmospheric sound propagation effects over varying terrain, such as hills and mountainous regions, as well as regions of varying acoustical impedance including water around the airfield.

4.6.2 MCB Hawaii Kaneohe Bay DNL Contours and Event Noise The AICUZ noise contours associated with the baseline (existing) operations are shown in Figure 4-3. The AICUZ noise contours for the prospective future conditions are shown in Figure 4-4. Historical AICUZ noise contours developed in 1990 and 2003 are presented in Figures 4-5 and 4-6, respectively, for informational and comparative purposes. Comparisons of the noise contours contained in the 1990 AICUZ or February 2003 AICUZ Study Update for MCBH Kaneohe Bay and the prospective future condition are shown in Figures 4-7 and 4-8, respectively. While the vast majority of the changes are over open water areas, a small expansion of the 65 dB DNL contour over land on Coconut Island and in the area of Kealohi Point is seen for the prospective 2018 condition. While these are the only off-installation land areas with higher noise contours, both Coconut Island and Kealohi Point are projected to have noise levels similar to the prior 1990 AICUZ condition as shown in Figure 4-5. Therefore, during this 23 year planning period, the noise levels have fluctuated but have not significantly increase over land areas. A comparison of the baseline and prospective future contours for MCB Hawaii Kaneohe Bay reflected in this AICUZ update, are also provided on Figure 4-9. The prospective future contours (AICUZ Noise Zones 2 and 3) are comparable but slightly expanded as compared to the baseline condition. Typical aircraft overflight (i.e., areas that aircraft fly over) event noise in terms of SEL and Lmax around Kealohi Point are summarized in Table 4-2. The loudest event noise would occur during the FA-18 A/C GCA pattern flight along Track 22G1 (see Figure 3-6) and C-5A arrival along Track 04A1 (see Figure 3- 2).

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Table 4-2 Comparison of Aircraft Overflight SEL and Lmax around Kealohi Point

Notes: Based on atmospheric conditions of 76.2° F, 74.5% RH, & 30.05 in Hg * P-8 Lmax estimated based on SEL-Lmax delta for P-3 conducting identical operation

Figure 4-5 1990 AICUZ DNL Contours (dB

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Figure 4-6 2003 AICUZ DNL Contours (dB)

Figure 4-7 Comparison of 1990 and Prospective (2018) DNL Contours

Figure 4-8 Comparison of 2003 and Prospective (2018) DNL Contours

Figure 4-9 Comparison of Baseline (2013) and Prospective (2018) DNL Contours