Source: https://jmrplens.github.io/phonometry/devices/ # Sources and devices Every prediction elsewhere in this documentation starts from a source descriptor, and this section is where those descriptors are measured. Its common thread is **emission**: numbers that belong to the device rather than to the room or the distance it is heard at. The **sound power and intensity** pages determine the central emission quantity, the sound power level: the figure that goes on a datasheet, feeds a room or outdoor prediction and is checked against noise-emission limits — including the route that reads it off the casing's own vibration when no microphone can be placed. The **electroacoustics** pages turn to devices that are *supposed* to make sound (amplifiers, loudspeakers and microphones) and to the broadcast programme they carry, and the **noise control** pages hold the path measures that quiet a machine once its emission is known. If you are here to measure a machine, start with [Sound Power](https://jmrplens.github.io/phonometry/emission/sound-power/) and let its decision guidance pick the route, which may end on an intensity probe or, when only vibration can be measured, on the radiating surface itself; read [Sound Intensity (p-p)](https://jmrplens.github.io/phonometry/emission/intensity/) when that route involves an intensity probe. If you are here to bench-test audio gear, go straight to [Electroacoustics](https://jmrplens.github.io/phonometry/electroacoustics/electroacoustics/); if you are here to level a programme, go to [Programme loudness](https://jmrplens.github.io/phonometry/broadcast/program-loudness/). ## [Sound power and intensity](https://jmrplens.github.io/phonometry/emission/) The total acoustic emission of a source, and the power flux it is built on. - [Sound Intensity (p-p)](https://jmrplens.github.io/phonometry/emission/intensity/): two-microphone sound intensity per IEC 61043 with the ISO 9614-1 field indicators. - [Sound Power](https://jmrplens.github.io/phonometry/emission/sound-power/): choosing the determination method and declaring the noise emission per ISO 4871. - [Sound Power by Pressure Methods](https://jmrplens.github.io/phonometry/emission/sound-power-pressure/): the enveloping surface of ISO 3744/3746 and the precision anechoic grade of ISO 3745. - [Sound Power in the Reverberation Room](https://jmrplens.github.io/phonometry/emission/sound-power-reverberation/): the direct and comparison methods of ISO 3741. - [Sound Power by Intensity Scanning](https://jmrplens.github.io/phonometry/emission/sound-power-intensity/): the on-site scanning of ISO 9614-2 and the ISO 9614-3 precision grade. - [Sound power from surface vibration (ISO/TS 7849)](https://jmrplens.github.io/phonometry/emission/vibration-sound-power/): the radiated power from the surface-averaged velocity level and the radiation factor, for the case where the machine cannot be moved, the room is not qualified and only an accelerometer is available: the Part 1 upper limit and the Part 2 engineering value. ## [Electroacoustics](https://jmrplens.github.io/phonometry/electroacoustics/) Amplifiers, loudspeakers and microphones on the bench, and the programme signal they carry. - [Electroacoustics: distortion and frequency response](https://jmrplens.github.io/phonometry/electroacoustics/electroacoustics/): the IEC 60268-3 distortion metrics and frequency-response estimation with coherence. - [Loudspeaker Characterisation (IEC 60268-5)](https://jmrplens.github.io/phonometry/electroacoustics/loudspeakers/): the sensitivity conventions, the radiating piston and the IEC 60268-5 characteristics fiche. - [Microphone Characterisation (IEC 60268-4)](https://jmrplens.github.io/phonometry/electroacoustics/microphones/): the sensitivity references, directional patterns and inherent noise of the IEC 60268-4 fiche. - [Swept-sine distortion and phase utilities](https://jmrplens.github.io/phonometry/electroacoustics/swept-sine-distortion/): harmonic separation and THD(f) from one exponential sweep (Farina / Novak synchronized swept-sine), and minimum phase, group delay and excess phase from a measured response. - [Broadcast](https://jmrplens.github.io/phonometry/broadcast/): the loudness problem solved with a measurement rather than a compressor, one gated number per programme and the range that says how much it moves. - [Programme loudness and true peak](https://jmrplens.github.io/phonometry/broadcast/program-loudness/): the ITU-R BS.1770-5 programme loudness and true-peak level with the EBU R 128 normalisation practice, EBU Mode metering and loudness range. ## [Noise control](https://jmrplens.github.io/phonometry/noise-control/) Industrial noise control on the path, between the machine and whoever hears it. - [Silencers](https://jmrplens.github.io/phonometry/noise-control/silencers/): reactive silencers by the four-pole method and the reactive-versus-dissipative choice. - [Duct-Borne Noise: Fan to Room](https://jmrplens.github.io/phonometry/noise-control/duct-path/): the end-to-end fan-to-room calculation against a room criterion, and the higher-order-mode cut-on that limits every plane-wave method. - [Room to Room: Partition, Receiving Room, Criterion](https://jmrplens.github.io/phonometry/noise-control/room-to-room/): the composed source-room to receiving-room chain and the transmission loss a partition or an enclosure needs to meet a noise criterion. - [Industrial Noise Control: HVAC and Enclosures](https://jmrplens.github.io/phonometry/noise-control/noise-control/): duct attenuation, flow noise and machine-enclosure insertion loss. ## What this section does not cover **No facility is qualified here.** ISO 3745's free-field qualification of an anechoic room, ISO 3741's reverberation-room qualification and IEC 61043's residual-intensity test of a probe are all assumed to have been done: the library warns on the coarse advisory criteria a standard states explicitly and grades a residual index you supply, but it does not certify a room or an instrument. The same boundary runs through the electroacoustics pages, which **reduce and report curves the laboratory supplies** rather than telling you how to acquire them, and through ISO/TS 7849, whose clauses 5 to 7 on instrumentation, installation and measurement positions are laboratory practice this library assumes. Three specific absences are worth knowing before you plan a job. ISO 9614-1's discrete fixed-point power summation is **not implemented at all** — only its field indicators are, reused by the scanning routes. Dissipative duct-lining silencers are **not modelled from liner properties** anywhere: the reactive elements are computed exactly within the no-flow plane-wave model, and the lined-elbow figure is a table lookup (Bies Table 8.11) and the plenum attenuation Wells' closed form driven by a declared mean absorption — neither is a liner model. And no page here predicts a panel's transmission loss: `enclosure_insertion_loss` combines a value you supply with the interior correction, and the prediction itself is [Insulation design](https://jmrplens.github.io/phonometry/buildings/design/). Editions are pinned rather than current in two places: the distortion metrics follow AES17-2015 and not the 2020 revision, and the microphone rated-characteristics report follows IEC 60268-4:2014 and not the 2018 one. Object-based audio (BS.1770-5 Annex 4) is out of scope, and the library implements no spatial renderer, so an object-based programme has to be rendered to a loudspeaker layout before it can be measured. ## Before and after these pages Every emission quantity here is computed from band levels or from an intensity pair, so the calibration, weighting and filtering behind them are in [Signal analysis](https://jmrplens.github.io/phonometry/signals/), and [Build a sound level meter](https://jmrplens.github.io/phonometry/signals/sound-level-meter/) runs that chain end to end on one runnable page. The derivations are split by physics rather than by topic: [sound power determination](https://jmrplens.github.io/phonometry/reference/theory/environment-transport/#sound-power-determination-iso-374437453746-iso-3741-iso-9614-23) is under Environment and transport, and [sound intensity](https://jmrplens.github.io/phonometry/reference/theory/signal-analysis/#sound-intensity-iec-61043) under Signal analysis. The electroacoustics and noise-control pages carry their derivations inline. 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.