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 models of the buildings section. The same group holds the one question that is not about sound at all: whether the shaking damages the building, which DIN 4150-3 answers with guideline values for the peak particle velocity, read at the dominant frequency of the measured vibration. ISO 4866 Annex D estimates a different frequency, the building’s own, from its height or its number of storeys when no modal measurement was made; the two meet only where the response is the building answering at that frequency, which is what the topmost floor plane and the floor of Clause 5.2 are about.

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. They also cover the one piece of hardware between the machine and the person: the seat, measured by the laboratory method of ISO 10326-1, which answers with a single ratio whether the seat attenuates what it is given or amplifies it.

Start with Mechanical mobility and the FRF family if you care about the noise a machine causes in a building, with Human Vibration if you care about the dose a person receives, or with Machine fault frequencies if you care about the condition of the machine itself.

From FRF vocabulary to the predicted level in a receiving room.

• Mechanical mobility and the FRF family (ISO 7626-1): receptance, mobility and accelerance with their reciprocals, and the SDOF reference resonator.
• Bending-wave transmission at plate junctions (Cremer/Craik/Hopkins): 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): the dynamic transfer stiffness of vibration isolators by the direct, indirect and driving-point methods, in one-third-octave bands.
• Sound power from surface vibration (ISO/TS 7849): radiated airborne power from surface velocity and a radiation factor.
• Structure-borne sound power of equipment (EN 15657): the reception-plate method and the plate-independent source quantities.
• Installed structure-borne sound (EN 12354-5): the receiving-room sound pressure level predicted from source and receiver mobilities.

Vibration transmitted to the human body, from daily exposure to spinal injury risk.

• 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): the spinal-response model and the probability of lumbar injury for vibration containing multiple shocks.
• What a seat does to the vibration (ISO 10326-1): the SEAT factor of a laboratory seat test, the correction to the input the test intended, and the transmissibility at resonance of the damping test.
• Verifying a human-vibration meter (ISO 8041-1): the tolerance band on each frequency weighting, the characteristic phase deviation, the running r.m.s. decay and the saw-tooth burst indications a conforming meter has to reproduce, and the personal vibration exposure meter of ISO 8041-2, graded with the same burst tables.

Turning a vibration spectrum into a diagnosis of the machine that made it.

• Machine fault frequencies: the characteristic bearing, gear and shaft frequencies, and the envelope analysis that finds them under the broadband noise of a running machine.

The instrument the German immission-control standards presuppose, the assessment it makes possible, and the railway measurements it is used for.

• Measuring vibration immission (DIN 45669-1): the KB weighting and the weighted vibration severity a DIN 4150 measurement is reported in, the tolerance bands a meter is graded by, and the Annex E assessment velocity that judges a building without a dominant frequency.
• Vibration next to a railway (DIN 45672): one train passage reduced to the numbers that can be compared, from the event value of an hour of traffic to the third-octave spectra and the narrow-band density behind them, and the ground constants from two wave speeds.
• Vibration and people in buildings (DIN 4150-2): the guide values a reading is held to by area and time of day, the order the standard reads them in, the assessment vibration severity of a day of exposure, and the rules for blasting, roads, railways and construction sites.
• Railway vibration by category of train (E DIN 4150-2): the draft that is to replace DIN 4150-2, a railway judged by category of train with a weighting factor per kind, and the rest of its changes.
• Predicting railway vibration (E DIN 45672-3): a railway’s spectrum on a floor built term by term before there is anything to measure, and the KB values formed from it.
• Predicting vibration before measuring (DIN 4150-1): the decay with distance, what a building does to it, and the shapes of a blast, a falling mass and a hall of machines.

• the clauses that are arithmetic

  An instrument is graded on the clauses that can be computed. Every criterion of ISO 8041-1 that is arithmetic is implemented, on the meter verification page: the tolerance band around each frequency weighting, the band-limiting stage on its own, the characteristic phase deviation, the running r.m.s. decay times and the 228 saw-tooth burst indications the standard prints. The rest of that standard, the indication, linearity, overload, temperature, humidity and electromagnetic clauses, is a set of laboratory tests on hardware, so a pass here is a necessary condition for conformity and never a certificate of it.

• 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 what people feel in a building. The 2003 edition of ISO 2631-2 deleted its predecessor’s guidance values on purpose, so for the human response to building vibration there are no acceptable magnitudes to compare against; what the library gives is the weighted magnitude, and the judgement stays with the assessor and the national code. The guideline values of DIN 4150-3 are a different question and are implemented: they are about damage to the structure, and keeping to one is not a certificate any more than exceeding one is a finding of damage.

• 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) 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, the linearity test of ISO 10846 (clause 7.7 of Parts 2, 4 and 5, clause 7.6 of Part 3) is described but not computed for you, and the Figure 11 nomograms of ISO 10846-4 for steel blocking masses are not tabulated.

Every quantity here starts from a record of acceleration or of velocity, which the signature of each function names, and most of them from a spectral estimate as well, so the filtering, the weighting curves and the spectral estimators behind them are in Signal analysis, and Spectral analysis is the page the machinery diagnostics build on. The derivations are in Vibration theory: 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? indexes it by the job and All guides lists every page with a line on each.