Aircraft and wind energy

Aircraft and wind turbines are noise sources important enough to have their own internationally negotiated metrics, each fixed to the last decimal by a certification or type-testing framework. The three pages of this section implement those frameworks, and they share a common anatomy: a rigorously standardised source descriptor, plus standardised propagation adjustments that place the source at a receiver.

Aircraft noise: Effective Perceived Noise Level covers fixed-wing certification. The EPNL of ICAO Annex 16 condenses a one-third-octave time history of a flyover into a single EPNdB value through perceived noisiness, a tone correction and a duration correction; the page adds the IEC 61265 measurement-system verifier, the SAE ARP 5534 atmospheric absorption used in the certification chain, and the ECAC Doc 29 noise-power-distance interpolation that turns certified levels into airport contour inputs.

Rotorcraft noise: the hemisphere method covers helicopters, whose strong directivity defeats a single-number source level. ECAC Doc 32 instead describes the source as a noise hemisphere (band levels on a grid of emission angles at a 60 m reference distance), propagates each ray with spherical spreading, atmospheric absorption and the Chien-Soroka ground effect, interpolates between the measured flight conditions along the track, and integrates the received history into the single-event SEL, LASmax and EPNL and their ground-grid contours.

Wind-turbine noise: sound power and tonal audibility covers IEC 61400-11 type testing: the apparent sound power level that refers the measured immission back to an equivalent point source at the rotor centre, and the tonal-audibility chain that decides whether a blade-passing, gearbox or generator tone is audible above its masking noise.

The shared physics connects outward: atmospheric absorption comes from the same ISO 9613-1 model as Outdoor Sound Propagation, and the wind-turbine tonality test is a cousin of the tonal-audibility methods in Psychoacoustics.

Pages in this section

• Aircraft noise: Effective Perceived Noise Level: the ICAO Annex 16 EPNL chain, IEC 61265 verifier, SAE ARP 5534 absorption and ECAC Doc 29 NPD interpolation.
• Rotorcraft noise: the hemisphere method: the ECAC Doc 32 noise-hemisphere source model, its propagation adjustments and the single-event metrics and contours.
• Wind-turbine noise: sound power and tonal audibility: the IEC 61400-11 apparent sound power level and tonal-audibility chain.