There is a better way for Noise Control!

Acoustics is not just an academic exercise from a university physics department or a way to get the best sound for music. Acoustics also is Noise Control, a way to improve everyday life! These pages explore some Noise Control possibilities, discuss potentials, analyze where it can be used and shed light on what can be accomplished with the noise simulation software SoundPLAN.


Noise Control Tasks


What can SoundPLAN do?

Community Noise Modeling

Land Use Planning

If cities don't regulate zoning and don't actively plan how to keep quiet areas quiet, it is a common occurrence for noise levels to gradually increase, eventually making sections of the urban environment much less desirable as living space.

If quiet zones are included in the master plan, then traffic planners can direct traffic to arterial roads to ensure traffic stays outside the residential neighborhood or they can regulate traffic speeds to ensure continued quiet during specific hours of the day or night.

END Type Noise Mapping

The European Noise directive (2002/49/EC) regulates the assessment and management of environmental noise. The directive requires all cities and agglomerations of more than 100,000 inhabitants to assess the noise exposure of people in their residence.

Additionally, the law requires studies of the very busy roads, railways and airports to determine the noise situation and its effects on the population.

The END requires this noise mapping be repeated every 5 years, so it only makes sense to prepare the data model in a way that allows updating the data (new traffic data, new population numbers, updated geometry where it changed) rather than starting anew every time.

END Noise Action Plans

The Action Plan phase is the twin to Noise Mapping. After mapping the noise situation, communities are obliged to determine how to improve the noise situation. This phase is supposed to include community involvement.

In the arsenal of Noise Action Plans, Hot Spot Analysis is a very important tool. Hot Spots are identified by poling the exposed population in a circle of 50 or 100 meters around every grid point in a Grid Noise Map. The result is a map which highlights noise problems even for a large area.

Improving the Community with Quieter infrastructure (buses and trucks)

Buses, city utility vehicles and garbage trucks can be noisy, and it is expensive to replace them with quieter models. To set a policy in place, a community planning department needs to deliver arguments of cost versus benefit for the improvements. A noise analysis and prognosis can pinpoint which school, hospital and neighborhood is improved by what margin for a variety of noise solutions.

Noise and Health - Preventing Stress Related Diseases

Noise is a form of stress to humans and animals and has been linked to hearing loss, sleep disturbance, cardiovascular and mental health problems, performance reduction, annoyance responses, and adverse social behavior. states, "First conservative and partial estimates show that at least 1.600.000 Disability Adjusted Life Years are lost every year in the EU, mostly due to road traffic (noise)."

Adverse Effects Greater for Children

High noise levels effect children more than adults. Pre-term birth has been linked to noise, as well as learning disability, difficulty to concentrate, and lower test scores. The World Health Organization web site has a lot of information pertaining to the effects of noise on children.

Noise simulations are the best means of quantifying the risk of an individual exposed to high noise levels in their residence. If the number of residence in a building is known, this number can be distributed evenly at the building facade and a facade noise map can be used to generate a statistics of noise exposure. If facade noise maps are made for each noise type, it is also possible to assign the health cost in proportion to road traffic noise, railway noise, aircraft noise and industry noise.

Minimize Construction Noise

Noise is not only a problem for road and railway traffic, but also during construction. Noise from rock blasting, earth moving and general construction noise can be very annoying. With proper noise control, much of the can be hidden behind berms or construction times arranged to minimize noise at night time. A proper study proposes different scenarios that show the best solutions.

Simulations versus Measurement

Before simulation software had reached its current level of proficiency and computers were fast enough to do the simulations, noise control engineers had no choice but to measure noise levels and then use their best judgment to control noise.

Today's simulations have distinct advantages over measurements. A measurement yields only one noise level. It is impossible to find how much noise came from which source. Measurements cannot occur in the planning process; the problem must physically be there to measure. Simulations allow one to work with "what-if scenarios" prior to building.


Seattle water front with the Alaska Viaduct

Seattle Alaska Viaduct plan from Washington State DoT

Noise Map for Stuttgart, Germany

Interstate 5 passing under the Seattle Convention Center

Noise Contour Map from a section of motorway

Hot Spot analysis showing numbers of inhabitants in noisy areas

Facade Noise Map in 3D

Train pass by in 2D

Train pass by in 3D

Noise Simulations

SoundPLAN 7.3 and SoundPLAN-Essential 3.0 - software products that simulate environmental noise.

SoundPLAN 7.3 is a modular program package so users purchase only what they need! It is very efficient for any size jobs, from small jobs to huge, complex models. Multiple scenarios, multiple input files and multiple output files are in the same project.

SoundPLAN-Essential 3.0 is the compact version of SoundPLAN, used for small to medium sized projects. It has the same calculation engine as its big brother.

The scope of noise simulations can range from just a neighborhood, to city wide assessments, or to country wide coverage.

The Seattle waterfront seen to the left is a good example showing that noise control is needed not only for residents in the adjacent buildings, but also for the potentially nice water front itself, which presently is subject to very high noise levels. The majority of noise comes from the Alaska Viaduct, an elevated structure with two levels for car traffic. The Alaska Viaduct was damaged by an earthquake and is now being replaced with a system of tunnels.

The value of the real estate in the waterfront will increase when the new tunnel is finished. The extent of this increase will be tied to the improvements in noise levels. SoundPLAN shows where noise levels have improved and by how much they have improved via its noise simulations and mapping capabilities. Before, after and difference noise maps show the improvements at street level. Facade Noise Maps show the improvements for buildings at all the various floor levels.

END Noise Mapping

SoundPLAN is used in many END type projects; the noise map of Stuttgart at night is an example. In the next section you can see an example of a small excerpt of the train noise map for an entire country - one of the many maps created when SoundPLAN was used for mapping the entire rail system throughout all of Germany for the first and second rounds of the END noise projects.

For further details of the END noise mapping, click END-Mapping.

Improving Community Noise - Costs and Benefits of noise solutions

The cost for quieter buses and other vehicles is quickly assessed. To show benefits of replacing noisy vehicles, take a Facade Noise Map showing noise from the existing buses combined with all other noise sources like cars and trains, and then create a noise map showing the noise with newer, quieter buses replacing the old, noise ones. The difference between the maps depicts the improvements. See more details at Facade Noise Map and Grid Noise Map.

Other Costs

When noise levels in a residential area are high, the rent charged for an apartment is often reduced. If noise is reduced, the price for rent and the value of the rental property increases. The Swiss Environmental Protection Agency (BAFU) has written this relationship of increasing noise levels and decreasing property values into formulas (WTI) that are easy to use. SoundPLAN's Spreadsheet allows the user to calculate the noise exposure with a Facade Noise Map and to apply the cost function for the property value. These costs are only a portion of the total cost of noise. Other cost factors are learning problems for children exposed to excess noise, plus direct health costs.

The WIT allows the consultant to weigh the cost of noise against the cost for controlling the noise!

Noise and Health

SoundPLAN can pinpoint areas with high noise levels. Grid Noise Maps and Facade Noise Maps are used to show the noise exposure of the population for each noise type, and these maps can be combined to show total noise exposure.

Health effects are dependent on the type of noise. Road traffic noise creates a more or less steady background noise that at high levels may carry the risk of not allowing the body any break from the noise. Train noise (at least for high speed trains) and aircraft noise are non-steady events often linked to sleep disturbance. The number of noise events per night can be extracted from the data of train noise and the aircraft statistics, and then can be correlated to noise problems found in an area.

Construction noise is unavoidable, but it, too, can be minimized. SoundPLAN's GeoDatabase is used to develop scenarios for the different phases of construction. Noise maps can depict each scenario. A detailed analysis of the noise sensitive receivers shows which of the machines/processes is responsible for noise problems. If possible, these operations then will be scheduled for the day time or the operators must investigate if quieter machines or shielding can mitigate the noise.

Simulations with SoundPLAN

With SoundPLAN scenarios can be quickly built by importing the model data from various sources such as GIS of Cad construction data or elevations from an aerial survey. Different scenarios are quickly developed and noise maps calculated.

For an engineer working in noise control the physics and the engineering is usually straightforward but this is not where the job ends. Planning always has a public relations component. You must sell your project to city council and in a broader sense to the public. With SoundPLAN you are in good hands here! Tables with detail information satisfy the requirements of the technical aspect while great 2D and 3D pictures and animations explain the findings to the general public. On the left an animated train pass by was generated by SoundPLAN to show the influence of the noise protection wall.

Noise Control for Infrastructure Projects

Assure a plan is compliant with the law

- as part of an Environmental Assessment Study

When a new Autobahn/Freeway/Motorway is planned in for the countryside, an environmental assessment study is usually part of the planning process. Communities should evaluate the noise impact especially for noise sensitive areas such as parks and recreational areas. Noise maps usually are the first step of the presentation.  If no noise limits are violated, the noise maps will be a good base line for the future. Often noise levels slowly creep up over time with no single cause. If a base has been established, it is possible to call for actions to re-establish the quiet zones the way they were at a specific time.

- as part of the general planning process

In many countries it is a requirement for new roads and railway lines or major upgrades to existing ones to limit the noise exposure of the population to a specified dB level for day, evening and night time. If planners think noise levels at the closest noise sensitive locations are close to the permitted level, a noise simulation is required. Usually these studies involve all other relevant sources in the area and tally the exposure in detail receiver by receiver.

Designing Noise Barriers for Road  and Rail

For railways, it is possible to ban noisy box cars with thread brakes, but this is expensive and it usually takes a long time to phase out the older rolling stock. For roads, noise control at the source is basically limited to quieter road surfaces.

The most common way to control noise from roads and railways is to construct a noise barrier in the propagation path. Finding the right noise barrier is an iterative process carried out for multiple receivers. As the barrier for one receiver will shield other receivers, it is critical to assess all barrier elements for all receivers simultaneously.

Geometrically, situations can sometimes be challenging, as seen in the picture to the right. It is best practice to simulate the effectiveness of a noise barrier with software. As it is often impossible to shield the entire facade, the situation should be presented with vertical noise maps. These maps determine what can be shielded with noise barriers and which windows need additional protection with noise control windows. For extreme situations such as the building to the right of the track, it is also necessary to assess the noise transmission through the facade.

Analyze Cost/Benefit for Quieter Road Surfaces

If the major noise problem is a single very busy road with high speed traffic, it is possible to control the noise by installing quiet, porous road surfaces. This type of road surface is more expensive than the conventional road surface, and usually requires more maintenance or shorter re-paving intervals than other surfaces, so it is paramount to have a cost/benefit analysis show the number of residents affected by the noise and to form a statistics of improvements.

Terrain model of Autobahn in SoundPLAN

Combination of noise from trains, streetcars and road traffic

Section of the train noise map for all of Germany

Optimization of noise control walls for trains

Wall Optimization for multiple receivers

Noise Control for Infrastructure Projects

Analyzing noise compliance

SoundPLAN's usage areas connect zoning laws to the buildings within a zone. If a building is in a residential area, the noise limits for residential buildings apply. When calculating a Facade Noise Map, it is possible to map the number of residents overexposed to noise. It is also possible to present a Grid Noise Map and compare it to the permitted noise levels. This is called a Conflict Map in SoundPLAN.

Wall Design - Design and Optimize

With SoundPLAN it is possible to import the data from the planning process. Elevation data are imported and triangulated into a continuous mesh, roads and railways are placed on top of the terrain and potential noise protection walls are generated on a parallel line to the road/railway alignment.

The model must include free field conditions and must also incorporate all buildings in the vicinity. SoundPLAN has tools to determine the height of the building as a difference between the raw data from an aerial survey (these points are on the roof) and the elevations of the ground. When the building heights are established, it is easy to determine the number of floors.

A Wall Design facade noise calculation is the best way to see how high a noise protection wall needs to be. For all the floors of residential buildings, calculations are made that iterate every section of the noise barrier in user defined steps.

An on-line wall selection then allows the user to optimize the noise protection wall, changing is shape on components for aesthetics and other aspects. The minimum noise protection wall that offers full protection for all residents is maintained.

As there are many reasons to customize wall height - layout, visibility at an intersection, and visibility to businesses - all situations must be considered. Walls look best when they don't start with too high elements and don't have gaps or end abruptly. These shapes create the sensation of an impulse, and although the dB numbers may not show it, the noise protection wall could then be perceived as detrimental to the wellbeing of the residents.

To view a noise optimization in progress, click: Wall-Opti

To read more about Wall Optimization with Wall Design, click: Details of Wall Design


Noise levels in an apartment can be controlled by erecting a barrier between the source and the building or by improving the acoustic quality of the building envelope. In SoundPLAN the option of the noise protection wall can be compared to the option of noise control windows. For an entire neighborhood the costs of both options can be compared, often the real world answer will be a mix of both options. With the Cost/Benefit diagrams any ratio of wall and windows can be simulated with an instant answer of the cost.

A diagram depicts the cost of the wall and the cost of the noise protection windows and the total cost. A good ratio of noise protection wall versus window upgrade can often be found with the WTI diagram.

The WTI tries to balance effectiveness and efficiency in a way that noise control is addressed and excessive heights of the noise barrier for a single receiver are avoided. A similar analysis can be done for road surfaces.


A screen capture from a Wall Dimensioning run

Watch the a wall to be optimized by SoundPLAN. After an off-line pre-calculation an interactive wall selection process is shown.

Noise Control in Architecture

Know a planned location is suitable (appropriate noise levels for hospitals, schools, kindergartens, public parks...)

Residential neighborhoods have noise limits that are most critical at night time; hospitals need to be shielded properly day and night while schools and kindergartens are only critical during the day.

If a new school or hospital is planned, it is wise to check if the proposed area is feasible or if the noise levels are too high. If the noise levels exceed the criteria, options must be chosen:

Build somewhere else
Control road noise using speed restrictions or ban certain vehicle types
Plan for quieter road surfaces
Have buildings shield noise sensitive areas
Build a noise protection wall to shield the facility
Plan for noise protection windows

Determine suitable building layouts to create quiet spaces

Often local food shops and small businesses are planned right into the residential neighborhood. If the shops, small offices and workshops are planned at the periphery to shield the core from excessive traffic noise, it may be a win - win situation for all parties, the shops have their exposure to the outside traffic and act as shields for the residential parts that enjoy the quietness behind them.

Select and optimize noise control windows

If it is not possible to build a noise protection wall, noise control windows are the next best choice. Sometimes a state or municipality offers special noise protection window upgrades along noisy road and railway corridors. For example, the German railway company had people in buildings exceeding certain noise thresholds along their tracks apply for a subsidy to upgrade the windows.

Noise levels outside windows are simulated in accordance to the standard used in the country. The noise inside the rooms is also simulated using the standards applicable in the country (24. BImSchV, VDI 2719, DIN 4109 for Germany and ISO 12354 everywhere else). The noise protection wall simulations regard the sizes of the window and the rest of the facade, the transmission for the window and the regular facade. The calculations are specific to the room size and usage.

As most noise control window upgrade programs have a set budget, it is paramount a cost estimate accompanies the acoustic evaluation. Itemized lists of window sizes for the different window classes can be created and fans for forced ventilation and other components should be considered.

City Planning Aspects

Solutions for excessive noise levels

Hospitals and schools may have been built before the traffic on the road increased to the levels that make the noise problem unbearable right now.

A noise protection wall is the only solution in a situation as on the left where noise levels are exceeding 70 dB on part of the hospital building. To cut the noise to 60 dB or below, a noise protection wall was designed on the property boundary wrapping around the main entrance and up well into to the side streets. The second situation depicts the scenario on the ground and it shows that the garden area is usable as a relatively quiet space, unfortunately the main entrance to the building is in the middle and cannot be shielded properly, and the entrance of the building is still in the bracket 60dB to 65dB.

The third picture shows the effect of the 4 meter high wall, with a decrease of levels up to 12 dB. 

New hospital, school, kindergarten or retirement home considerations

When planning a new facility, there are many more options compared to situations where the roads and buildings already exist and can only be modified. The best option for a new facility on a busy road would be to locate the administrative offices and utility buildings near the road and have the rooms that require silence in the back. The administrative building would act as a noise protection wall for the more sensitive parts of the building.

In SoundPLAN, it is possible to generate an unlimited number of scenarios like this. They are called Situations. A Situation can consist of fixed and variant Geo-files. All Situations can be the same except for the variant placement of the hospital / school / shielding buildings. Elevation information, the road and the other buildings are fixed. SoundPLAN allows an unlimited number of input files and result files in a project. Difference maps require only the definition of the geometry and operand files. To learn about the capabilities of the Geo-Database, click: GeoDB

Window Dimensioning

The hospital in our example had enough space for a noise protection wall. Otherwise they would have needed to install noise control windows. In our high-rise example, the architects wanted to know what type of windows to install. A Facade Noise Map is the perfect tool to determine this. The color scale of the facade receivers shows windows classes in steps of 5 dB. SoundPLAN's Building Acoustics module allows users to regard the Rw for windows and the rest of the facade. With the usage and size of the room, it is possible to calculate the noise levels inside the room in accordance to ISO 12354. To learn more, click on Building Acoustics Outside.

Industry Noise

Noise in the Work Place Employee Noise Exposure

In many countries the noise limits for traffic noise are less than for industrial noise, making it vital that a noise assessment log keep track of where noise initiates. Industry noise can come from various sources, factories, power plants, electrical generation, transformer stations, wind parks, open cast mining operations, refineries, gas compressor stations, ports and trucking companies to name a few. The noise is usually frequency dependent and can vary with time. Noise levels are assessed either for day/night or day/evening/night; sometimes extra assessments such as the comprehensive Lden are used.

Determine where workers are required to use hearing protection

The main problem in noisy plants is finding and documenting the 85 dB noise contour line. In areas where noise levels exceed 85 dB, workers must wear hearing protection. Often fines are levied if the 85 dB line is not clearly marked. Signs must make it clear to employees that hearing protection is required. It is irrelevant if the high noise levels are inside or outside a factory building; all that matters is that the 85 dB contour line is enforced.

If a plant has areas that may be close to or above 85 dB, it is wise for the plant to invest in a noise study to define all areas where hearing protection is required. An alternative solution is to provide workers with noise dosimeters that keep track of their daily dosage of noise. A well-studied and documented noise policy is better than paying for lawsuits from workers with hearing problems and paying for disability because of tinnitus and hearing loss.

Shield office spaces and other noise sensitive areas from excess noise

Often there are conflicting requirements for shop floors. A hall without partitioning walls and other obstacles may be very flexible in its usage, but a hall without absorbent walls and no baffles on the ceiling may be excessively noisy. If there are rooms with desks for computer or paperwork or for employee's breaks, it may be a good idea to install movable or permanent partitions with absorbent materials on both sides. Half height or full height walls must have enough weight so the noise transmission through the wall is less than the noise passing over the wall.

Noise in the work place is not limited to a noisy factory floor. If enough equipment is installed in office hallways, noise levels can increase enough to make it difficult to concentrate on work inside adjacent rooms. Fans from air conditioning boxes are also loud. Only measurements can show all noise problems and simulations lead the way to solve those problems. In general, one must analyze the absorption of the room shell and the ratio of absorbent and reflective materials in the room and try to reduce the sound power of heating and ventilation equipment and other equipment.

Reduce noise outside a factory

Noise problems originating inside a factory building can affect the surrounding neighborhood. Noise propagating into the neighborhood from open windows and doors or other entries in to or out of the factory may force a complete indoor factory noise evaluation for the sake of a quiet neighborhood.

Trucking companies have a similar situation; truck noise on public roads has a much lower problem than truck noise at the trucking company itself where the assessment is as industrial noise rather than transportation noise.  This, too, leads to further assessment.

Industry noise needs to be scrutinized very carefully to determine when the noise occurs as operations at night must be quieter by 10 dB than during the day. Sometimes noise problems are solved simply by not having certain processes worked on at night.

Noise from wind farms have also become an issue. Special standards (IOA) deal with the noise from the tip of the blades whirling around the hub. These special guidelines are implemented in SoundPLAN.

Factory building in 3D with cross-sectional noise map

2D noise map before noise control

2D noise map after noise control

Difference map with/without noise control

View animation in a higher resolution, click on: Refinery

Noise Maps for Wind farms

SoundPLAN Industry Noise

SoundPLAN is the only noise modeling software with a full integration of industry noise indoors and outdoors. It is a seamless integration, making it possible to simulate the noise inside the factory floor, calculate the noise levels on the inner walls and use the noise transmission from inside to outside to assess how much noise the factory will emit into the neighborhood. Because some of the data are known or derived from measurements for many projects, it is possible to enter into the simulation at any step of the process.

All calculations indoors and outdoors are available for octave bands, third octave bands and single mean frequency. Point, line and area sources are available; they can be associated with various forms of directivity and time history over the 24 hours of the day. A library system hosts the data for sound power, noise absorption, transmission and directivity.

Noise in the work place

For calculating noise inside a factory building, a modified version of the German VDI 3760 is available. Where the original VDI 3760 only foresaw simple buildings, SoundPLAN extended the geometry. For example, room to room transmission through an open door, the addition of partitioning walls and the calculation of screening from full and half height walls was added to the basic standard.

The SAK curve makes it possible to evaluate the reverberation properties frequency by frequency and to compare these to the free field conditions. This is a valuable tool and a starting point to fix noise problems in the room.

The outside shell of the factory building does not have to be defined by a single material; windows and doors can be added, and it is even possible to model an open window in the door. For each material, the transmission spectrum can be selected from the library. During the noise calculation, SoundPLAN evaluates the sizes of the inlaid sources and automatically subtracts them from the rest of the shell. As there are no difference spectra, the result tables can depict the correct noise level contribution for each of the partial sources. To read more about the Indoor noise, click: Indoor Noise

Industrial Noise Outdoors

For calculating Industry Noise, SoundPLAN offers close to 20 accepted standards ranging from the ISO 9613 to the Nord2000 and Concawe. To read more, click: Industry Noise

SoundPLAN needs the sound power for calculating industrial noise. Measured data often provides only the sound pressure level, the distance from the noise source, and the information about the type of measurement. SoundPLAN has provisions to convert data to sound power. Filtering frequency data from dB to dB(A) or any other filter is possible.

Calculations can be made for Single Receivers, Facade Noise Maps, Cross Sectional Noise Maps, Grid Noise Maps and Meshed Maps. Result tables are a good tool to get an itemized list of the contributions of each source to the receivers. Spreadsheets make it easy to open these contributions and evaluate different noise control options at the source.

Grid Noise Maps can be used to depict a specific scenario or to show the differences between before and after scenarios.

Meshed Maps for industry noise have special provisions to present the map frequency by frequency or with a specific frequency band. A single calculation will enable you to generate a drawing with multiple views of the same facility depicting noise of different frequencies.

Wall Design's optimization features for transportation noise are the same as Expert System's to optimize industry noise. Expert System helps users rank receivers in accordance to the noise infringement, or to rank the contributions for each receiver so work can be focused on fixing the major noise problems. To read more, click Expert System in the additional module section at the end of the website.

With the SoundPLAN version 7.4 it is now also possible to set the sound power from a source either via a computer assisted measuring tool or set teh power entirely through formulas that are based on technical parameters. Sources such as pipe bundles can be modeled much easier!

Simulate Alarm Sirens and Public Address Systems

Functioning alarm systems for tsunamis and hazardous industrial sites

For a warning or alarm siren, the noise levels at any given point must exceed 66 dB and should be 10 dB louder than the ambient noise levels. Some horns have a strong directivity that must be considered when modeling alarm systems.

Many operators of hazardous sites also want to know what is happening in the event one of the alarm horns fails. How is the coverage of the system in case of a single failure.

Ensure public address systems work

To properly design public address, one must consider the type of background noise, its time signature and frequency mix. If there is more than one speaker, the delay between the speakers can cause interferences that must be considered for proper speaker placement.

Alarm system coverage inside a factory building

Can you hear where the street car is going?

To know if a public address system is audible, the entire scenario is simulated, including car and bus traffic, streetcars and the adjacent train line. The loudspeakers are also simulated as sources with a frequency dependent sound power and directivity. One noise map is calculated with just the background sources and another has both the background noise and the loudspeakers.

A difference map is then created from these maps. In places where the difference map shows less than 10 dB difference between both maps, the public address system can't be heard properly.

For the factory to the left, two scenarios were developed, one for normal operations and one for an emergency event. A regular noise map was created for both scenarios showing all sources available. Then a secondary noise map was created including background and siren noise. In the difference plot to the left, the areas in dark red show where the difference between the ambient and ambient plus sirens is less than 6 dB. These areas are places where workers with hearing protection might not hear the alarm. More or stronger sirens are needed in the red areas.

Aircraft Noise

The dominant standard to simulate aircraft noise worldwide is the ECAC Doc. 29 3rd edition. Some countries in Europe use different forms of the AzB and Switzerland has its own calculation standard. In Australia, aircraft noise is compared to the ambient noise levels.

Public relations

Aircraft noise is one of the least accepted forms of noise. Everyone drives a car or rides a train, so these forms of noise are more accepted. Airports often install noise monitoring stations and/or produce noise maps as a measure of good will. If complaints are received, then the airport administration can say, "We are on it!" even if little is done.

For tracking noise over a long period of time, it is very helpful to an airport to show not only single noise events but also to show the noise level classes for all aircraft for day and for night operations.

Minimize departure and approach noise

Airports use published procedures for approach and departure patterns. The elevation profile is dictated by the type of aircraft. The glide slope is fixed by navigation instruments for heavy, commercial traffic and by optical glide slope indicators for lighter aircraft flying a visual approach.

The flight track is fixed in the immediate vicinity of the airport, but there is some leeway where aircraft turn in the direction of their destination. When modeling the approach and departure patterns for the middle section of the climb and descent, it is wise to study the option of slight course change to avoid residential neighborhoods.

Aircraft start and land into the wind. When the wind is calm, air traffic control decides which runway will be used for take offs and which one for landing. The effects of this choice can be studied with a noise map for the different scenarios.

Show aircraft noise violations

Many airports have a noise monitoring system that shows excessive noise levels. However, a noise control officer also needs an analysis of the flight track and noise simulation to determine which company is responsible for the noise infringement and to issue a fine to the airline.

The best way to operate a noise monitoring system is in combination with a recording system that records the radar tracks of individual flights. This way the complaint can be effectively verified with the recording and the noise simulation can be used to determine if this was a violation or a weather phenomenon.

Minimize noise from run-up pens and other operations

Aircraft make noise even when not flying. Taxiing must be considered when evaluating airport noise. It is not wise to have lots of airplanes on a taxiway waiting for take-off.

Testing aircraft engines after maintenance also makes a lot of noise. Testing usually is in run-up pens that have absorbent material to help minimize noise.

Even aircraft parked at the gate emit noise because a turbine is running to provide electricity and air conditioning for the plane.

The airport itself has noise from air conditioning, baggage handling, refueling, pumping waste products, passenger vehicles and so forth.

Aircraft noise modeling must include all these operations and sometimes even off-airport noise such as the take-off pattern from a helicopter on the roof of a hospital.

Noise Map from Istanbul airport

Combination of aircraft noise, taxiing, run-up and traffic noise

Recorded radar tracks as basis of a noise map for aircraft noise

Noise statistics at an airport

Helicopter noise in 3D

Noise animation of an approaching military jet

Aircraft Noise

Modeling of all the noise sources is integrated so users can make comprehensive noise maps of flying aircraft, taxiing aircraft, engine test boxes, all the other airport noise sources plus all the other noise sources within the study area. The first graphic to the left shows transportation noise from cars and trains plus airport noise. It is clear the transportation noise is much less pressing than the aircraft noise.

The second aircraft noise map is of the Istanbul Atatuerk Airport in Turkey. The zone with 65-75 dB clearly infringes several residential neighborhoods. The noise levels 55-65 cover a big area, especially for the take-off to the north. This noise map should be important to city planners making sure the area should no longer include more residential areas but could be used for industrial and commercial usage instead.

The third noise map is of an airport with radar tracking. All tracks for take offs and landings are recorded by the radar facility. The data include an identifier for the aircraft, the type of aircraft, and the aircraft's speed, position and altitude. This data is used to make a noise map for the individual flight to track violations or to form a backbone for the more theoretical corridor for approaching and departing aircraft.

Making a comprehensive noise map with all radar tracks for a single day is the best way to document the noise levels in the vicinity of an airport. The time resolution of the radar track recording is too coarse to use without proper interpolation of the data. SoundPLAN interpolates data points to form sensible flight paths.

Along with the usual array of noise maps, SoundPLAN also generates information for individual receivers with full statistics of the noise events for the day. Noise levels are collected in dB classes and the distribution of noise events is presented with a breakdown of aircraft categories. The shape of the distribution is characteristic for the location, flight operation (which runway was used for takeoff and which one for landing) and also for the mix of aircraft that flew that day.

How does the aircraft noise model work?

To model aircraft noise, the engineer first defines the airport using the geographical location of the airport as the reference point. It must have the same coordinate system as the rest of the data (buildings, elevation information, etc.)

An airport has one or multiple runways, which are defined with the runway reference point, the orientation, and length of the runway. Each runway flight track is defined with location and an elevation profile. The flight track is described with a sequence of headings and arcs left and right to get to the heading.

Each flight tracks requires operational data that assign an aircraft type and additional operational data to it. The number of approaches and departures is part of the operational data.

The acoustical data are linked to a performance database that sets the acoustical and performance characteristics for a particular aircraft. Databases are delivered with the software, and can also be imported from other sources (INM, for example) or created and modified by the user.

Helicopter Noise

Noise is not a phenomenon for fixed wing aircraft only; helicopters are also noisy, especially when operations are off airport at a hospital, for example. Helicopter operations are sometimes more difficult to describe. The picture to the left shows the helicopter moving backwards off a roof platform and then assumes regular flight at a safe altitude.

Noise Animation

With the SoundPLAN calculations of aircraft noise it is possible to create level/time histories. For a Grid Noise Map these time histories can be used to create the picture of the instant noise level. These animations are saved to an AVI file such as the animation on the left of a military aircraft that fly over the airport, enter the pattern and then land.

As the instant noise level is taking the speed of sound into account, the diagrams assume strange shapes when the aircraft is flying on a curved path.

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