NOISIM (Last update: 5/13/96 JKK)
1. Primary Model Category
Modeling and Display of Aircraft Community Noise Impact.
2. Summary
NOISIM is a real-time aircraft simulator with the ability to model and display the community noise impact of a specific trajectory that is flown. The model implicitly includes any aircraft-specific constraints and also includes the effect of wind or other atmospheric conditions on aircraft performance and noise propagation.
3. Input Requirements
NOISIM requires a pre-programmed flight plan or real-time procedure entry through a control display unit, mode control panel, keyboard, or manual stick inputs. A Graphical User Interface is used to plot and calculate noise impact. Flight plans can be pre-programmed using a text input file. Wind conditions can also be prescribed in a text input file. Changes in wind conditions can be scripted (e.g., to simulate windshear events).4. Outputs
NOISIM displays the community noise impact as a series of noise contours in A-Weight Sound Pressure Level (dBA) or Sound Exposure Level (SEL). These contours are overlaid on a map derived from USGS hydrography and land use data. The model calculates the total area exposed to different noise levels, the land area exposed to different noise levels, and the population exposed to different noise levels. Other derived metrics such as the Equivalent Sound Level (Leq) and Time Above a specified threshold of A-Weighted Sound (TA) can be calculated.
5. Major Assumptions
The aircraft performance and engine parameters at each iteration step are calculated as if the engine is at steady state.
6. Computational Characteristics
Code exists (written in C). Software has been developed for Silicon Graphics platforms. Documentation quality is currently in draft for the prototype version. Calculation of the noise impact takes 15-20 minutes of post processing computation.
7. Modularity and Flexibility
The simulator allows rapid prototyping of different cockpit display, navigation systems, aircraft parameters, and engine parameters. It is currently configured with 737 performance and engine parameters, and 747-400 instrumentation. Modifications to the dynamic model may involve significant recoding. Topographical data for the Boston metropolitan area is currently included to determine land area noise impact. Noise calculation routines are modularized and can be separated from the aircraft simulation.
8. Status
The model is intended as an experimental tool, is a first prototype, and is not mature. An extensive graphical user interface is in place and is easy to use for the display and calculation of noise impact.
9. Extent of Model Verification
In a series of simulations designed to mimic the radar trajectory of a 737 operating out of Boston Logan Airport, the noise simulations agree to within 2 dBA with recorded data from noise monitoring stations around the airport.
10. Principal Applications
Investigation of the trades between noise impact and aircraft performance. Development of prototype noise abatement procedures.
11. Availability
Contact: John-Paul Clarke, MIT, (617) 253-7748, johnpaul@mit.edu, or Prof. R. John Hansman, MIT, (617) 253-2271, rjhans@mit.edu
12. Information for Model Evaluation
Summary is based on a review by the author of NOISIM. No documentation is currently available.
13. Summary Evaluation
NOISIM is a prototype version of an all-in-one aircraft noise simulator developed to investigate the trades between noise impact and aircraft performance, and evaluate prototype noise abatement procedures. The model has realistic flight dynamics and implicitly includes the performance constraints which limit the maneuvers that may be performed in a noise abatement procedure. It also provides researchers with a tool to determine how piloted aircraft flight procedures affect the community noise impact. NOISIM uses actual piloted flight data to determine noise impact, rather than an assumed trajectory that is followed perfectly. Thus, NOISIM appears to be better able to show expected variations in noise impact due to aircraft tracking performance or wind conditions than the Integrated Noise Model (INM).
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