Source: https://jmrplens.github.io/phonometry/guides/sections/outdoor-sound/ Outdoor sound assessment has two halves: predicting the level a source delivers to a distant receiver, and judging the character of the sound that actually arrives. The two pages of this section take one half each. [Outdoor Sound Propagation](/phonometry/guides/outdoor-propagation/) is the prediction half. Starting from a source's **sound power**, the ISO 9613-2 general method subtracts, octave band by octave band, every mechanism that attenuates sound on its way: geometrical divergence, atmospheric absorption (supplied by the pure-tone coefficient of **ISO 9613-1**), the ground effect and barrier screening, with a meteorological correction for long-term averages. The page keeps the per-term breakdown visible, so a prediction is never a black box: you can see exactly which mechanism buys how many decibels at which frequency. [Spherical ground effect and advanced barriers](/phonometry/guides/ground-barriers/) goes underneath the ISO 9613-2 fits to the wave acoustics they approximate: the Weyl-Van der Pol spherical-wave reflection coefficient of a finite-impedance ground, and barrier diffraction by the Kurze-Anderson Fresnel number, the exact rigid half-plane, thick barriers and the coherent four-path barrier on the ground, all resolving the frequency-dependent interference the octave-band terms smooth away. [Impulsive-sound prominence (NT ACOU 112)](/phonometry/guides/impulse-prominence/) is the assessment half. Noise containing distinct impulses (hammering, riveting, pile driving) annoys more than a steady sound of the same LAeq, and the Nordtest method quantifies that: from the onset rate and level difference of each impulse it computes a predicted **prominence**, and converts it into the graduated adjustment KI that is added to the measured LAeq in a rating level. The surrounding machinery lives nearby: the rating levels and Lden that assessments end in are covered in [Integrated and Statistical Levels](/phonometry/guides/levels/), the tonal counterpart of the impulsive adjustment in [Objective audibility of tones in noise](/phonometry/guides/tone-audibility/), and the sources that feed a propagation calculation in [Sound Power](/phonometry/guides/sound-power/) and the [Aircraft and wind energy](/phonometry/guides/sections/aircraft-wind/) section. ## Pages in this section - [Outdoor Sound Propagation](/phonometry/guides/outdoor-propagation/): ISO 9613-1 atmospheric absorption and the ISO 9613-2 general method with a per-term octave-band attenuation breakdown. - [Spherical ground effect and advanced barriers](/phonometry/guides/ground-barriers/): the Weyl-Van der Pol spherical-wave ground reflection and wave-theoretic barrier diffraction (Kurze-Anderson, exact rigid half-plane, thick barriers and the coherent four-path barrier on the ground). - [Impulsive-sound prominence (NT ACOU 112)](/phonometry/guides/impulse-prominence/): the predicted prominence of impulsive sounds and the graduated LAeq adjustment KI.