What do you need to measure?

The rest of this site is organised by subject, which is right once you know which subject owns your problem and unhelpful before that. This page is the other way round: the job on the left, the guide that answers it on the right, with the standard the guide implements so you can tell before clicking whether it is the one your client, your reviewer or your regulator will accept.

If your job is not listed, All guides is the full inventory, and the glossary goes the other way again: you have a symbol from a report and you want the guide that computes it.

From a recording

The job	Where it is answered
I have a WAV recording and I need A-weighted levels, $L_{Aeq}$ and the percentile levels	Build a sound level meter — IEC 61672-1 and IEC 61260-1, the whole chain on one runnable page, from the calibrator tone to the class check of every stage
My numbers are not in pascals and I do not know what they are	Calibration and dBFS — the calibrator tone, the sensitivity in pascals per digital unit, the pre/post drift rule and the digital dBFS alternative
I need a spectrum rather than a level	Filter Banks for band levels (IEC 61260-1), Spectral analysis for a density estimate

Rooms and buildings

The job	Where it is answered
The reverberation time of a room I can get into	Measuring the Room Impulse Response for the acquisition (ISO 18233 sweeps and the interrupted-noise alternative), then Room Acoustics for $T_{20}$, $T_{30}$, EDT, $C_{50}$, $C_{80}$ and the rest of ISO 3382-1
The reverberation time of a room that does not exist yet	Reverberation-time prediction — the Sabine family, with the section that says which model to use and when every model fails; Sound absorption in enclosed spaces when a design report has to cite EN 12354-6
Whether a room is quiet enough for what happens in it	Room-noise criteria — NC, RC Mark II and NR, and the section on choosing between them
$R_w^{\prime }$ or $D_{nT,w}$ of a partition I measured on site	Field Insulation Measurement (ISO 16283-1/-2) for the measurement, then Insulation Ratings (ISO 717-1/-2) for the single number and the adaptation terms
Proof that a wall meets the Spanish CTE DB-HR	Spanish Building Code — the required quantities, which one each requirement is written against, and the compliance check
The insulation of a building I am still designing	Predicting Sound Insulation (EN 12354), and Detailed prediction when the flanking paths have to be itemised

Machines, products and installations

The job	Where it is answered
The sound power of a machine	Sound Power — start here whatever the facility: its “Choosing a method” section routes to the pressure (ISO 3744/3745/3746), reverberation-room (ISO 3741), intensity (ISO 9614) or surface-vibration (ISO/TS 7849) method
A declared emission value for a datasheet or a CE file	Declaring the noise emission — ISO 4871, the declared A-weighted level $L_{WAd}$ and its uncertainty $K_{WA}$
How much a silencer, an enclosure or a duct run will attenuate	Silencers, Industrial noise control for enclosures and HVAC, Duct paths
A loudspeaker, microphone or amplifier measured to its standard	Electroacoustic measurements — IEC 60268-3/-4/-5
The loudness of a programme in LUFS	Programme loudness and true peak — ITU-R BS.1770-5 and EBU R 128

Environment and transport

The job	Where it is answered
$L_{den}$, $L_{night}$ or a rating level from an environmental survey	Environmental noise levels — ISO 1996-1/-2, the indicators and the adjustments that go on top of them
Source power for a road or railway noise map	CNOSSOS-EU road traffic source emission and railway source emission — Annex II of 2002/49/EC, the source side of it
How much a distance, a barrier or the weather takes off	Outdoor propagation (ISO 9613-2), Ground effect and barriers, Atmospheric refraction
Whether a wind farm is compliant	Wind turbine noise — IEC 61400-11 and the tonal audibility assessment
The certification level of an aircraft flyover	Aircraft noise: EPNL — ICAO Annex 16, and Airport noise contours for the map around the airport

People

The job	Where it is answered
Whether a worker is over the daily exposure limit	Occupational Noise Exposure — ISO 9612, the $L_{EX,8h}$ and its uncertainty
Loudness in sones, or sharpness, roughness and fluctuation strength	Loudness (ISO 532-1/-2/-3), then Sound quality metrics
Whether a tone in a noise is audible, and by how much	Tone audibility (ISO/PAS 20065, DIN 45681) and Tone prominence, whose section on which metric to use covers both
The STI of a public-address system	Speech Transmission Index — IEC 60268-16, direct and indirect (STIPA)
A seat, floor or hand-arm vibration record against the Directive	Human Vibration — ISO 2631-1 and ISO 5349-1, and Multiple-shock vibration for ISO 2631-5

Materials, and under water

The job	Where it is answered
The absorption coefficient of a sample	Sound Absorption Measurement and Rating for the reverberation room (ISO 354, ISO 11654), Impedance Tube for normal incidence (ISO 10534-2)
The airflow resistivity or the dynamic stiffness of a layer	Airflow resistance (ISO 9053-1/-2), Dynamic stiffness (EN 29052-1)
How much a diffuser scatters	Diffusers and scattering — ISO 17497-1/-2, and the difference between the two coefficients
A ship’s radiated noise, or the exposure of a pile-driving campaign	Underwater acoustics (ISO 17208, ISO 18406) then Marine-mammal noise exposure
How far a sound carries in the sea	Underwater propagation, and Underwater propagation solvers when a range-dependent field is needed

When more than one method is right

Several guides carry the decision themselves, in a section written for a reader who has the problem and not yet the method. They are worth opening before the guide you think you need:

• Choosing F, S or I — which exponential time weighting a measurement calls for.
• Which filter architecture should I choose? — Butterworth against the four alternatives, and what each trades away.
• Choosing a criterion: NC, RC Mark II or NR.
• Choosing a model, and when every model fails — Sabine, Eyring, Millington, Fitzroy, Arau.
• Choosing a method — the four routes to sound power and what each facility allows.
• Choosing a loudness model — Zwicker, Moore-Glasberg and Sottek.
• Which measure, and when — STI against the intrusive and non-intrusive measures.
• Which tonality metric, and when.
• Direct or indirect — full-matrix STI against STIPA.
• Choosing a model — normal modes, rays and the parabolic equation.

Before you measure anything

Two habits save more measurements than any of the pages above. Record the calibrator tone through the same chain, before and after, and treat the difference as your drift bound — Getting Started shows why an uncalibrated level is not approximately right but arbitrary. And read the “What this guide covers” block at the end of whichever guide you land on: it states which clauses, annexes and methods are implemented and which are not, which is the question a reviewer will ask first.