aircraft.atmospheric_absorption

One-third-octave-band atmospheric absorption for aircraft noise (SAE ARP 5534).

Aircraft noise certification (14 CFR Part 36, ICAO Annex 16 Vol. I) works with one-third-octave-band spectra, and correcting a measured flyover to reference atmospheric conditions requires the band attenuation over the propagation path. The pure-tone attenuation coefficient is the ISO 9613-1 one (identical, per ARP 5534 §3.1) already provided by phonometry.air_absorption.air_attenuation; this module adds the SAE Method (ARP 5534 §3.2.2), a regression that turns the pure-tone mid-band path-length attenuation into the one-third-octave-band attenuation and stays consistent with the ISO/ANSI Exact Method well beyond the 50 dB limit of the older Approximate Method.

• sae_band_attenuation — the one-third-octave-band attenuation over a path, returned as a AircraftBandAttenuation with a .plot().

Source (clean-room, implemented from the standard text): SAE ARP 5534 (2021), Application of Pure-Tone Atmospheric Absorption Losses to One-Third-Octave-Band Data, Eqs. 7-10; the pure-tone coefficient is ISO 9613-1:1993.

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AircraftBandAttenuation

AircraftBandAttenuation(
    frequency: NDArray[np.float64],
    band_attenuation: NDArray[np.float64],
    midband_attenuation: NDArray[np.float64],
    coefficient: NDArray[np.float64],
    path_length: float,
    temperature: float,
    relative_humidity: float,
    pressure: float,
)

One-third-octave-band atmospheric attenuation over a path (SAE ARP 5534).

Attributes

Name	Description
frequency	Nominal one-third-octave-band centre frequencies, in Hz.
band_attenuation	SAE-Method band attenuation δ_B per band, in dB.
midband_attenuation	Pure-tone mid-band path-length attenuation δ_t = α·s per band, in dB (ISO 9613-1 coefficient).
coefficient	Pure-tone mid-band attenuation coefficient α per band, in dB/m.
path_length	Propagation path length s, in metres.
temperature	Air temperature, in degrees Celsius.
relative_humidity	Relative humidity, in percent.
pressure	Ambient atmospheric pressure, in kPa.

AircraftBandAttenuation.plot()

AircraftBandAttenuation.plot(
    ax: Axes | None = None,
    *,
    language: str = 'en',
    **kwargs: Any,
) -> Axes

Plot the band and pure-tone mid-band attenuation versus frequency.

sae_band_attenuation

sae_band_attenuation(
    frequencies: NDArray[np.float64] | list[float],
    path_length: float,
    *,
    temperature: float = 25.0,
    relative_humidity: float = 70.0,
    pressure: float = 101.325,
) -> AircraftBandAttenuation

One-third-octave-band atmospheric attenuation (SAE ARP 5534, SAE Method).

Computes the pure-tone attenuation coefficient at each band’s exact mid-band frequency (ISO 9613-1, f_{m,i} = 10^{i/10}), forms the mid-band path-length attenuation δ_t = α·s and maps it to the band attenuation δ_B with the SAE-Method regression (Eqs. 7-8).

Parameters

Name	Description
frequencies	Nominal one-third-octave-band centre frequencies, in Hz (standard range 50 Hz-10 kHz; the method extends to 25 Hz-20 kHz).
path_length	Propagation path length s, in metres (>= 0).
temperature	Air temperature, in degrees Celsius (SAE window ~6-32 °C; default 25 °C, the ARP 5534 reference point).
relative_humidity	Relative humidity, in percent (SAE window ~20-95 %; default 70 %).
pressure	Ambient atmospheric pressure, in kPa (default 101.325).

Returns: An AircraftBandAttenuation.

Raises

Exception	When
ValueError	If the inputs are invalid.