Theory

The theory reference collects the derivations, clause references and design decisions for the areas whose mathematics is shared across many guides. A theory page maps an implemented method back to the clause, equation and table of the standard or textbook it comes from, states the physics behind each correction term and the assumptions that bound it, and gives the reference values the validation suite checks against. It does not show workflows: that is what the guides are for. The natural pattern is to arrive here from a guide when a term needs justifying, or to read a domain page first when deciding whether a method applies at all.

The six domains are not independent. Signal analysis underpins everything, because every other page consumes band levels, weighting curves and time integration from it; perception and hearing explains the curves several other pages then use as weightings; rooms and buildings, materials and surfaces and environment and transport are the three application domains, and they share the sound-power and absorption machinery between them; vibration supplies the structural quantities that panel and flanking prediction rest on.

Several areas keep their theory inside their guides rather than here, because the derivation and the single method it serves would otherwise be separated for nothing. That is the case for the underwater modules (Underwater Acoustics, Underwater Propagation, Underwater Propagation Solvers and Marine-Mammal Noise Exposure); for the aircraft certification and contour methods in Aircraft noise; for the CNOSSOS-EU road and railway emission models in Environmental sources; for the IEC 60268 electroacoustic measurements and the BS.1770 broadcast chain in Electroacoustics and Broadcast; for the silencer, duct-path and room-to-room models of Noise control; and for the FDTD and elastic solvers, whose numerical method, stability bound and dispersion rule are developed on the wave simulation pages themselves. Everything below is listed with the sections each domain page hosts.

Signal Analysis

Where the band edges, the filter magnitude responses and the weighting curves come from, and the numerical reasons the bank is built as a decimated cascade of second-order sections; also the time-integration, intensity and GUM uncertainty derivations.

Perception and Hearing

The longest of the six: the equal-loudness contours, the excitation-pattern and masking models behind loudness and sound quality, the modulation-transfer chain of the STI and the band-importance and audibility construction of the SII, then the hearing-threshold statistics and the damage model built on them.

Rooms and Buildings

Five groups: the ANSI S12.2 criterion curves, the impulse response and the parameters read off it, sound insulation and absorption as measured, the same quantities as predicted, and the uncertainty that qualifies either.

Materials and Surfaces

The characterisation standards rather than the prediction models: what a scattering coefficient and a diffusion coefficient each measure and why they must not be swapped, how an in-situ road measurement separates the reflection in time, and the definitions behind the laboratory absorption and impedance quantities.

Environment and Transport

The descriptors and the attenuation terms: how the ISO 1996-1 indicators are built, what the NT ACOU 112 prominence criterion measures, where each ISO 9613 term comes from, and — filed here rather than under devices, because the mathematics is the same — the sound-power determination derivations and the ISO 9612 occupational-exposure uncertainty.

Vibration

The shortest: the human-vibration weightings and dose measures with the ISO 2631-5 spinal model, plus the point-mobility and radiation-efficiency results the structure-borne pages use.

Created and maintained by José Manuel Requena Plens ORCID All projects