# Presentation: 352695

## Use of One-Third Octave-Band Spectral Data in Community Noise Models

**Environmental Measurement & Modeling Division - Acoustics Facility**

**Use of One-Third Octave-Band Spectral Data in Community Noise Models**

- 2003 International Congress and Exposition on Noise Control Engineering
- Session PA-3: Environmental / Community Noise
- Christopher J. Roof

## PRESENTATION OVERVIEW

- Background
- One-Third Octave-Band Data: Spectral Class Concept
- Spectral Class Development
- Spectral Class Validation & Verification
- Potential Capabilities / Limitations Using Spectral Data

## BACKGROUND

- Aircraft Noise Modeling Guidance Documents
- Society of Automotive Engineers (SAE) “Procedure for the Calculation of Airplane Noise in the Vicinity of Airports” AIR-1845
- European Civil Aviation Conference (ECAC) “Report on Standard Method of Computing Noise Contours around Civil Airports” Doc 29
- International Civil Aviation Organization (ICAO) “Recommended Method for Computing Noise Contours around Airports” Circular 205
- Reference Conditions
- Noise-Power-Distance Curves (NPDs)
- Acoustically Soft, Flat Ground Surface
- Reference Atmosphere

## BACKGROUND (cont.)

- Airport Conditions Vary from Reference Conditions
- Ground Type
- Hard Ground
- Mixed Hard / Soft Ground
- Terrain Features
- Non-Standard Temperature / Humidity
- Predictions Extrapolated from NPD Distances
- Advanced Models Can Address these Issues
- Acoustic Data Requirements
- Non-Acoustic Data Requirements

## BACKGROUND (cont.)

- More Advanced Models: Tradeoffs
- Potentially Greater Accuracy
*	**	**   **versus*
- Increased Data Collection Requirements
- Potential Instability
- (Sensitivity to Model Inputs vs. Actual Aircraft Changes)

## SPECTRAL CLASS CONCEPT

- Representative Aircraft Spectra Required
- Databases Include 100’s of Aircraft*    **INM v 6.1 = 248*
- Older Aircraft
- Newer Aircraft (Proprietary Data)
- Smaller “Chapter 10” Aircraft
*Can Aircraft Be Grouped Together for       Calculations Requiring Spectral Data?*

**Notes:**
FAR36 “Appendix G” ~ ICAO “Chapter 10”

## SPECTRAL CLASS DEVELOPMENT

- Step #1: Group Similar Aircraft/Engine Combinations

- Airframe
- # Engines
- Engine Bypass Ratio
- Engine Type

## SPECTRAL CLASS DEVELOPMENT (cont.)

- Step #2: Visual Inspection

## SPECTRAL CLASS DEVELOPMENT (cont.)

- Step #2: Visual Inspection, Normalized

## SPECTRAL CLASS DEVELOPMENT (cont.)

- Step #3: Verification

## SPECTRAL CLASS DEVELOPMENT (cont.)

- Step #4: Final Spectral Class

## POTENTIAL CAPABILITIES

- Atmospheric Absorption         *Under SAE Review*
- Ground Impedance Effects    *Under SAE Review*
- Terrain Shielding
- Building Shielding
- Refraction

## SPECTRAL CLASS VALIDATION

- Airbus INM Data Submission Comparison
- NPD Comparison
- Actual Airbus NPD's  (Integrated Process)
- Actual Spectra  (Simplified Process)
- Spectral Class  (Simplified Process)

***Compared for SAE Atmosphere***

***Compared for other Atmospheres***

- A300-622R
- A310-304

- A321-232
- A330-343

- (Atmospheric Absorption)

## SPECTRAL CLASS VALIDATION (cont.)

- 2 Power Settings (1 Approach; 1 Takeoff)
- Maximum Sound Level (LASmx) and Sound Exposure Level (LAE)
- Multiple Atmospheric Conditions

- 15C / 55 %RH
- 25C / 55 %RH

- 15C / 70 %RH
- 25C / 70 %RH

- (Atmospheric Absorption)

## SPECTRAL CLASS VALIDATION - Results

- (Atmospheric Absorption  - cont.)

## SPECTRAL CLASS VALIDATION - Results

- (Atmospheric Absorption  - cont.)

## SPECTRAL CLASS VALIDATION - Results

- (Atmospheric Absorption  - cont.)

## SPECTRAL CLASS VALIDATION - Results

- (Atmospheric Absorption  - cont.)

## SPECTRAL CLASS VALIDATION - Results

- (Atmospheric Absorption  - cont.)

## PRESENTATION SUMMARY

- Spectral Class Concept Successfully Implemented
- Improved Calculations
- Simple “Grouped” Spectral Data Approach
- Lays Groundwork for Future Model Improvements
- Guidance Documents Should Be Updated to Reflect the State-of-the-Art
*	**	**Including Tradeoffs: Increased Complexity vs. Benefit*

## CURRENT INM

- Integrated Noise Model Version 6.1
- 	> 700 Users
- 	> 50 Countries

*Total Distribution*

*Distribution by Sector*

**Notes:**
12 users in South Korea

## REFERENCES

- Integrated Noise Model (INM) Version 6.0 User’s Guide
- Integrated Noise Model (INM) Version 6.0 Technical Manual
- Spectral Classes for FAA’s Integrated Noise Model, Version 6.0
- Society of Automotive Engineers (SAE), Aerospace Information Report (AIR), SAE-1845, “Procedure for the Calculation of Airplane Noise in the Vicinity of Airports”
- European Civil Aviation Conference (ECAC) Doc 29
- International Civil Aviation Organization (ICAO) Circular 205

## CONTACT INFORMATION

**CONTACT INFORMATION**

- Christopher J. Roof
- U.S. Department of Transportation
- Volpe National Transportation Systems Center
- Acoustics Facility
- DTS-34
- PH: (617) 494-6344
- FX: (617) 494-3208
- _[Roof@volpe.dot.gov](mailto:Roof@volpe.dot.gov)_
- http://www.volpe.dot.gov/acoustics/