26. ISO 80000-8 — Acoustics🔗

The sixth part specified in full is ISO 80000-8, Acoustics. Every item — all of 8-1 … 8-17, including the sub-suffixed pressure pair (8-2.1, 8-2.2) — is catalogued: the logarithmic frequency range, static and sound pressure, the sound-particle kinematics (displacement, velocity, acceleration), volume flow rate, the sound-energy cluster (energy density, energy, power, intensity), sound exposure, the two impedances, the three logarithmic levels, and the reverberation time — each carrying its exact source as data: the part, the printed item designation, the principal quantity symbol, and the coherent SI unit symbol. Only citation locators are recorded; no normative content from the licensed standard is reproduced. The defining mathematics of selected remarks is specified in the sibling module Part8.DefiningRelations.

Acoustics brings two faces of the catalogue's central thesis, and — unusually — its boundary. The logarithmic levels (sound pressure level, sound power level, sound exposure level) are each 10·lg(quantity / reference), ratios on a logarithmic scale reported in the decibel: dimension one, three distinct kinds the dimension functor collapses to a single point. A genuine dimension collision has sound pressure and sound energy density carry the same dimension M·L⁻¹·T⁻² — force per area equals energy per volume — while staying distinct kinds. And the boundary: the two homonymous impedances are told apart by their dimension, the case where the necessary discriminator is, this time, also sufficient.