Source: https://jmrplens.github.io/phonometry/aircraft/ # Aircraft noise Aircraft noise is computed under internationally negotiated methods of two kinds. **Certification** fixes a single number per aircraft type to the last decimal, at reference points a standard places around the runway. **Contour methods** take that certified fleet and predict what an airport does to the ground around it. The four pages of this section cover both, and they share a common anatomy: a rigorously standardised **source descriptor** — a spectral time history, a noise-power-distance table or a noise hemisphere — plus standardised **propagation adjustments** that place the source at a receiver. [Aircraft noise: Effective Perceived Noise Level](https://jmrplens.github.io/phonometry/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 and the SAE ARP 5534 atmospheric absorption used in the certification chain. [Airport Noise (ECAC Doc 29)](https://jmrplens.github.io/phonometry/airport-noise/) picks the aeroplane up from there: the noise-power-distance tables, the per-segment corrections of a flight path (impedance, lateral attenuation, engine installation, duration, noise fraction and start-of-roll directivity) and the single-event contour over a ground grid. [Rotorcraft noise: the hemisphere method](https://jmrplens.github.io/phonometry/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. [The ANP fleet database](https://jmrplens.github.io/phonometry/anp-fleet/) closes the loop on the two above: the noise-power-distance tables and default trajectories EASA and EUROCONTROL publish for real aircraft types, ready to feed the Doc 29 chain without writing a table by hand. The shared physics connects outward: atmospheric absorption comes from the same ISO 9613-1 model as [Outdoor Sound Propagation](https://jmrplens.github.io/phonometry/environment/propagation/outdoor-propagation/), and the same type-testing logic governs [Wind-turbine noise](https://jmrplens.github.io/phonometry/environment/sources/wind-turbine-noise/), which is filed with the other environmental sources: its IEC 61400-11 apparent sound power level and tonal-audibility chain answer the same question for a source that is not an aircraft. That tonality test is in turn a cousin of the methods in [Psychoacoustics](https://jmrplens.github.io/phonometry/perception/psychoacoustics/). Start from the question. To check an aeroplane against a certification limit, or to understand where the published numbers for a type come from, start with the EPNL page. To predict what a movement does at a street address, use the Doc 29 page, with the ANP page supplying the aircraft data. For helicopters the hemisphere page replaces both. Read the fixed-wing pages in that order: the EPNL page defines the certified metric, the Doc 29 page turns certified aeroplanes into ground contours from tables written by hand, and the ANP page replaces those hand-written tables with the published fleet data. The rotorcraft page stands on its own — a different standard and a different source model — and can be read first if helicopters are what you came for. The three metrics are not interchangeable. EPNL is a *certification* metric of one aeroplane at one prescribed point; SEL and LASmax are *single-event* assessment metrics at an arbitrary receiver; neither is the long-term index a land-use study is finally judged on. ## Pages in this section - [Aircraft noise: Effective Perceived Noise Level](https://jmrplens.github.io/phonometry/aircraft-noise/): the ICAO Annex 16 EPNL chain, the IEC 61265 verifier and the SAE ARP 5534 absorption. - [Airport Noise (ECAC Doc 29)](https://jmrplens.github.io/phonometry/airport-noise/): the NPD engine, the single-event segment chain and the ground-grid SEL contour. - [Rotorcraft noise: the hemisphere method](https://jmrplens.github.io/phonometry/rotorcraft-noise/): the ECAC Doc 32 noise-hemisphere source model, its propagation adjustments and the single-event metrics and contours. - [The ANP fleet database](https://jmrplens.github.io/phonometry/anp-fleet/): the EASA tables of noise-power-distance curves and default trajectories that run the Doc 29 chain for a real aircraft type. ## What this section does not cover **Single events only.** The Doc 29 chain builds single-event contours; it does not assemble the cumulative multi-event indices — an Lden-style sum over a full flight schedule — that a complete noise-contour study needs on top of them. That last step is where a land-use decision is actually made, and it is not here. **No aircraft is modelled from first principles.** NPD tables and noise hemispheres are *inputs*: the library interpolates the tables published for a type and does not synthesise them from engine data, and the ANP database is read and never written (version 2.3 ships as-is). Of the ANP entries, only those with fixed-point profiles have a ready-to-use trajectory, because turning a procedural-step departure into a flight path needs the ICAO Doc 9911 flight-mechanics performance model, which is not implemented. **Three specific gaps.** Rotorcraft hover, idle and taxi run on the Table 3 derived sources, but the guidance's last resort for a type with no hover data at all (two side-line level-flight microphones corrected to the 150 m hover circle by the Annex 16 integrated method) is not modelled. The measurement-system verifier checks IEC 61265:1995 and not the superseding 2018 edition. And sonic boom is not touched anywhere in the library. Finally, the CNOSSOS-EU aircraft source of sections 2.6 and 2.7 is **not** implemented: aircraft noise here is the ICAO and ECAC family, which is a different set of models from the road and rail sources of [Environmental sources](https://jmrplens.github.io/phonometry/environment/sources/), and the two must not be mixed inside one strategic map without saying so. ## Before and after these pages Every level on these pages is built from band levels, so the filtering, weighting and calibration that produce them are in [Signal analysis](https://jmrplens.github.io/phonometry/signals/), and [Build a sound level meter](https://jmrplens.github.io/phonometry/signals/sound-level-meter/) runs that chain end to end on one runnable page. The derivations for aircraft noise are not in the theory reference: they stay inside the guides above, beside the flight geometry that motivates them. If you arrived here from a search and want the shape of the whole library, [What do you need to measure?](https://jmrplens.github.io/phonometry/start/tasks/) indexes it by the job and [All guides](https://jmrplens.github.io/phonometry/) lists every page with a line on each.