Source: https://jmrplens.github.io/phonometry/guides/sections/structure-borne/ A machine fixed to a building radiates sound twice: directly from its own vibrating surface, and indirectly by injecting **structure-borne power** into the structure, which carries it away and re-radiates it in distant rooms. The five pages of this section cover both paths: one estimates the direct radiation from the surface vibration itself, and the other four characterise the second, sneakier structure-borne path end to end, from describing the vibration and characterising the isolators to quantifying the power and predicting the level a listener finally hears. The language comes first. [Mechanical mobility and the FRF family (ISO 7626-1)](/phonometry/guides/mechanical-mobility/) defines the motion-per-force frequency-response functions (receptance, mobility, accelerance and their reciprocals) that every later standard speaks, with the closed-form SDOF resonator as the reference and the ISO 7626-2 measurement acceptance criteria. Source and receiver *mobilities* are what decide how much power actually couples across an interface, which is why this vocabulary matters. Two pages then characterise the path elements. [Transfer stiffness of resilient elements (ISO 10846)](/phonometry/guides/transfer-stiffness/) measures the dynamic transfer stiffness of the isolators, mounts and hoses inserted precisely to break the transmission path, by the direct and indirect (transmissibility) methods. [Sound power from surface vibration (ISO/TS 7849)](/phonometry/guides/vibration-sound-power/) handles the direct radiation: the airborne power estimated from surface velocity and a radiation factor, without any acoustic measurement. The last two pages close the chain on the source and the receiver. [Structure-borne sound power of equipment (EN 15657)](/phonometry/guides/structure-borne-power/) measures what a machine injects, via the reception-plate method, and derives the plate-independent source quantities (blocked force, characteristic power level, free velocity). [Installed structure-borne sound (EN 12354-5)](/phonometry/guides/installed-structure-borne/) consumes exactly those quantities, couples them through source and receiver mobilities, and predicts the sound pressure level in the receiving room, which is where this section meets the [sound insulation](/phonometry/guides/sections/sound-insulation/) models. ## Pages in this section - [Mechanical mobility and the FRF family (ISO 7626-1)](/phonometry/guides/mechanical-mobility/): the FRF family, conversions and the SDOF reference resonator. - [Bending-wave transmission at plate junctions (Cremer/Craik/Hopkins)](/phonometry/guides/junction-transmission/): the wave-approach transmission coefficients for rigid X, T, L and in-line junctions, their angular average and the derived coupling loss factor and Kij. - [Transfer stiffness of resilient elements (ISO 10846)](/phonometry/guides/transfer-stiffness/): dynamic transfer stiffness of isolators by the direct and indirect methods. - [Sound power from surface vibration (ISO/TS 7849)](/phonometry/guides/vibration-sound-power/): radiated airborne power from surface velocity and a radiation factor. - [Structure-borne sound power of equipment (EN 15657)](/phonometry/guides/structure-borne-power/): the reception-plate method and plate-independent source quantities. - [Installed structure-borne sound (EN 12354-5)](/phonometry/guides/installed-structure-borne/): the predicted receiving-room level from installed equipment.