Source: https://jmrplens.github.io/phonometry/vibration/ # Vibration and structure-borne sound Vibration matters to acoustics three times over. First as a **source of sound**: a pump or fan bolted to a building injects structure-borne power that travels through walls and floors and re-radiates as audible noise rooms away. Second as a **human exposure** in its own right: vibration transmitted to a standing, seated or hand-gripping person is measured, weighted and limited much like noise, with its own metrics and legal action values. Third as a **diagnosis of the machine itself**: the same spectrum that feeds the first two questions also names the bearing, gear or blade that produced it, because every periodicity in it belongs to something that turns, meshes or passes, at a frequency fixed by the geometry. The **structure-borne sources** pages follow the source chain in order. The frequency-response-function family of ISO 7626 (receptance, mobility, accelerance) is the vocabulary; the wave-approach transmission coefficients of a plate junction describe the structure the power then runs through; the transfer stiffness of ISO 10846 characterises the resilient elements that interrupt that path; ISO/TS 7849 estimates the airborne power a vibrating surface radiates directly; EN 15657 measures the structure-borne power a machine injects into a reception plate; and EN 12354-5 assembles all of it into the sound pressure level predicted in a receiving room. That final prediction is also where this section hands over to the [sound insulation](https://jmrplens.github.io/phonometry/buildings/insulation/) models of the buildings section. The **human vibration** pages share the measurement philosophy of a sound level meter, applied to acceleration: frequency weightings that reflect body response, running and integrated averages, and dose quantities compared against the action and limit values of Directive 2002/44/EC, plus the dedicated spinal-response model for vibration containing repeated shocks. Start with [Mechanical mobility and the FRF family](https://jmrplens.github.io/phonometry/structural/mechanical-mobility/) if you care about the noise a machine causes in a building, with [Human Vibration](https://jmrplens.github.io/phonometry/human/human-vibration/) if you care about the dose a person receives, or with [Machine fault frequencies](https://jmrplens.github.io/phonometry/machinery/machine-diagnostics/) if you care about the condition of the machine itself. ## [Structure-borne sources](https://jmrplens.github.io/phonometry/structural/) From FRF vocabulary to the predicted level in a receiving room. - [Mechanical mobility and the FRF family (ISO 7626-1)](https://jmrplens.github.io/phonometry/structural/mechanical-mobility/): receptance, mobility and accelerance with their reciprocals, and the SDOF reference resonator. - [Bending-wave transmission at plate junctions (Cremer/Craik/Hopkins)](https://jmrplens.github.io/phonometry/structural/junction-transmission/): the frequency-independent wave-approach coefficients for rigid X, T, L and in-line junctions, their angular average and the derived coupling loss factor and Kij, and the experimental route that measures the same coupling loss factors by power injection. - [Transfer stiffness of resilient elements (ISO 10846)](https://jmrplens.github.io/phonometry/structural/transfer-stiffness/): the dynamic transfer stiffness of vibration isolators by the direct and indirect methods. - [Sound power from surface vibration (ISO/TS 7849)](https://jmrplens.github.io/phonometry/devices/emission/vibration-sound-power/): radiated airborne power from surface velocity and a radiation factor. - [Structure-borne sound power of equipment (EN 15657)](https://jmrplens.github.io/phonometry/buildings/design/structure-borne-power/): the reception-plate method and the plate-independent source quantities. - [Installed structure-borne sound (EN 12354-5)](https://jmrplens.github.io/phonometry/buildings/design/installed-structure-borne/): the receiving-room sound pressure level predicted from source and receiver mobilities. ## [Human vibration](https://jmrplens.github.io/phonometry/human/) Vibration transmitted to the human body, from daily exposure to spinal injury risk. - [Human Vibration](https://jmrplens.github.io/phonometry/human/human-vibration/): whole-body and hand-arm weightings (ISO 8041-1), r.m.s. and dose measures (ISO 2631-1), daily exposure A(8) (ISO 5349) and the Directive 2002/44/EC values. - [Multiple-shock whole-body vibration (ISO 2631-5)](https://jmrplens.github.io/phonometry/human/multiple-shock-vibration/): the spinal-response model and the probability of lumbar injury for vibration containing multiple shocks. ## [Machinery](https://jmrplens.github.io/phonometry/machinery/) Turning a vibration spectrum into a diagnosis of the machine that made it. - [Machine fault frequencies](https://jmrplens.github.io/phonometry/machinery/machine-diagnostics/): the characteristic bearing, gear and shaft frequencies, and the envelope analysis that finds them under the broadband noise of a running machine. ## What this section does not cover **No instrument is type-tested.** ISO 8041-1's own subject, the design and type-testing of human-vibration meters, is not implemented: only its frequency weightings are taken from it, so a class verdict for a hand-held meter is not something this library can give. **No severity verdict is issued for a machine.** The machinery pages predict *where* a line would be, never whether it is present or whether the machine is in trouble: the amplitude criteria that turn a present line into an assessment — crest-factor and kurtosis trending, and the velocity severity bands of ISO 10816 / ISO 20816 — are outside the library, as are rotor balancing (ISO 21940) and order tracking. **Nor is one issued for a building.** The 2003 edition of ISO 2631-2 deleted its predecessor's guidance values on purpose, so there are no acceptable magnitudes for building vibration to compare against; what the library gives is the weighted magnitude, and the judgement stays with the assessor and the national code. Two structural predictions are idealisations rather than measurements. The junction transmission coefficients are a closed-form result for a rigid, simply supported junction — the *measured* vibration reduction index of ISO 10848 is [Laboratory flanking transmission](https://jmrplens.github.io/phonometry/buildings/insulation/flanking-lab/) — and the FRF page returns element-wise free reciprocals, correct for a driving-point or single-path use but not a full FRF matrix, with no impact-hammer processing (ISO 7626-5) and no blocked matrix quantities. On the isolator page, parts 4 and 5 of ISO 10846 are not implemented, and two of the standard's validity checks (the blocking-mass inequality and the clause 7.6 linearity criterion) are described but not computed for you. ## Before and after these pages Every quantity here starts from an acceleration record and a spectral estimate, so the filtering, the weighting curves and the spectral estimators behind them are in [Signal analysis](https://jmrplens.github.io/phonometry/signals/), and [Spectral analysis](https://jmrplens.github.io/phonometry/signals/spectra/spectral-analysis/) is the page the machinery diagnostics build on. The derivations are in [Vibration theory](https://jmrplens.github.io/phonometry/reference/theory/vibration/): the human-vibration weightings, the ISO 2631-5 shock model and the point mobilities and radiation efficiency. If you arrived here from a search and want the shape of the whole library, [What do you need to measure?](https://jmrplens.github.io/phonometry/start/tasks/) indexes it by the job and [All guides](https://jmrplens.github.io/phonometry/) lists every page with a line on each.