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This document describes methods for calculating the attenuation of sound due to line-of-sight blockage or shielding from non-level terrain. This method applies to sound propagating from an airplane to locations on the ground during ground roll, climbout after liftoff, and landing operations. AIR1845 and AIR5662 provides guidance for modeling aircraft noise at airports with flat terrain. In reality, many airports are surrounded by non-level terrain that may result in attenuation (or shielding) of sound at some receptors. This noise blockage can be accounted for with the line-of-sight blockage calculation, based on the difference in propagation path length between the direct path and propagation path over the top of terrain feature. The purpose of this aircraft information report is to provide a method that accounts for the attenuation due to line-of-sight blockage of aircraft noise by terrain features.

Satisfactory measurements of noise in personnel-occupied rotorcraft cabins may require test techniques different from those prescribed for other types of aircraft (ARP1323) because rotorcraft operate under significantly different flight conditions. Recommendations of this ARP apply to the recording of acoustical data on magnetic tape and the subsequent processing and analysis of the recorded data.

Satisfactory measurements of noise in personnel-occupied rotorcraft cabins may require test techniques different from those prescribed for other types of aircraft (ARP1323) because rotorcraft operate under significantly different flight conditions. Recommendations of this ARP apply to the recording of acoustical data on magnetic tape and the subsequent processing and analysis of the recorded data.

This SAE Aerospace Recommended Practice (ARP) provides engineering methods that can be applied to monitoring aircraft noise and operations in the vicinity of airports using either attended or unattended monitoring systems, as well as methods for validation of measurement results from permanent systems. Part 1 provides guidance on the components, installation and administration of permanent systems and guidance on analysis of data collected from temporary monitoring of aircraft noise. Part 2, this part, describes both system screening tests and detailed test methods for validating the data reported by permanently installed systems. This document is intended as a guide toward standard practice and is subject to change with experience and technical advances.

This SAE Aerospace Recommended Practice (ARP) provides engineering methods that can be applied to monitoring aircraft noise and operations in the vicinity of airports using either attended or unattended monitoring systems, as well as methods for validation of measurement results from permanent systems. Part 1 provides guidance on the components, installation and administration of permanent systems and guidance on analysis of data collected from temporary monitoring of aircraft noise. Part 2, this part, describes both system screening tests and detailed test methods for validating the data reported by permanently installed systems. This document is intended as a guide toward standard practice and is subject to change with experience and technical advances. Potential users include: airport proprietors, airport neighbors, federal, state and local government agencies, equipment vendors and other public bodies and officials.

This SAE Aerospace Recommended Practice (ARP) provides engineering methods that can be applied to monitoring aircraft noise and operations in the vicinity of airports using either attended or unattended monitoring systems, as well as methods for validation of measurement results from permanent systems. Part 1 provides guidance on the components, installation and administration of permanent systems and guidance on analysis of data collected from temporary monitoring of aircraft noise. A separate document, Part 2, describes both system screening tests and detailed test methods for validating the data reported by permanently installed systems. This document is intended as a guide toward standard practice and is subject to change with experience and technical advances. Potential users include: airport proprietors, airport neighbors, federal, state and local government agencies, equipment vendors and other public bodies and officials.

This SAE Aerospace Recommended Practice (ARP) provides engineering methods that can be applied to monitoring aircraft noise and operations in the vicinity of airports using either attended or unattended monitoring systems, as well as methods for validation of measurement results from permanent systems. Part 1 provides guidance on the components, installation and administration of permanent systems and guidance on analysis of data collected from temporary monitoring of aircraft noise. A separate document, Part 2, describes both system screening tests and detailed test methods for validating the data reported by permanently installed systems. This document is intended as a guide toward standard practice and is subject to change with experience and technical advances.

This document describes a practical system for a user to determine observer-to-aircraft distances. These observer-to-aircraft distances can be either closest point of approach (CPA) distances during field measurements or overhead distances during acoustic certification tests. The system uses a digital camera to record an image of the subject aircraft. A method of using commercial software to obtain the distance from such an image is presented. Potential issues which may affect accuracy are discussed.

This method estimates noise for both single and tandem main rotor helicopters except for approach where it applies to single rotor designs only. It does not apply to coaxial rotor designs. Application is limited to helicopters powered by turbo-shaft engines and does not apply to helicopters powered by reciprocating engine, tip jets or other types of power plants. It provides noise information using basic operating and geometric information available in the open literature. To keep the method simple, it generates A-weighted sound levels, precluding the necessity for spectral details. The method prescribes estimates for typical helicopter operations; certain maneuvers may produce noise levels different from those estimated. Estimates are given for the maximum sound levels at 4 ft (1.2 m) height above the ground. For aircraft in forward flight, the estimate is given for an aircraft at an altitude of 500 ft (152 m) on a path directly over the observer.

This method estimates noise for both single and tandem main rotor helicopters except for approach where it applies to single rotor designs only. It does not apply to coaxial rotor designs. Due to lack of available data, application of the method has not been evaluated for application to tiltrotor, or other VTOL configurations, when operating in the helicopter mode. Since there are substantial differences between helicopter rotors included in the data base, and tiltrotor rotors, application to VTOL configurations other than helicopters is not advised. Application is limited to helicopters powered by turboshaft engines and does not apply to helicopters powered by reciprocating engine, tip jets or other types of power plants. It provides noise information using basic operating and geometric information available in the open literature. To keep the method simple, it generates A-weighted sound levels, and Sound Exposure Levels precluding the necessity for spectral details.

This method estimates noise for both single and tandem main rotor helicopters except for approach where it applies to single rotor designs only. It does not apply to coaxial rotor designs. Due to lack of available data, application of the method has not been evaluated for application to tiltrotor, or other VTOL configurations, when operating in the helicopter mode. Since there are substantial differences between helicopter rotors included in the data base, and tiltrotor rotors, application to VTOL configurations other than helicopters is not advised. Application is limited to helicopters powered by turboshaft engines and does not apply to helicopters powered by reciprocating engine, tip jets or other types of power plants. It provides noise information using basic operating and geometric information available in the open literature. To keep the method simple, it generates A-weighted sound levels, and Sound Exposure Levels precluding the necessity for spectral details.

Recommendations of this Aerospace Recommended Practice (ARP) are not intended to satisfy the more detailed and stringent requirements of aircraft design development. Also, they may not be directly applicable to general or private aviation aircraft where special restraints on measurement locations and procedures may exist. However, many of the principles and standards discussed may apply to these aircraft. The recommended procedure for sound pressure level measurements in aircraft involves the recording of data on magnetic tape for subsequent processing and analysis after the flight. Sound level meter/octave-band analyzer measurements, because of inherent inaccuracies associated with manual data readings, are not as precise as those obtained from a tape-recorder/time integrating analyzer system and are, therefore, precluded from this recommended practice.