Source: https://jmrplens.github.io/phonometry/guides/sections/aircraft-wind/ 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](/phonometry/guides/aircraft-noise/) 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](/phonometry/guides/rotorcraft-noise/) 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](/phonometry/guides/wind-turbine-noise/) 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](/phonometry/guides/outdoor-propagation/), and the wind-turbine tonality test is a cousin of the tonal-audibility methods in [Psychoacoustics](/phonometry/guides/sections/psychoacoustics/). ## Pages in this section - [Aircraft noise: Effective Perceived Noise Level](/phonometry/guides/aircraft-noise/): the ICAO Annex 16 EPNL chain, IEC 61265 verifier, SAE ARP 5534 absorption and ECAC Doc 29 NPD interpolation. - [Rotorcraft noise: the hemisphere method](/phonometry/guides/rotorcraft-noise/): 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](/phonometry/guides/wind-turbine-noise/): the IEC 61400-11 apparent sound power level and tonal-audibility chain.