How to specify a noise monitoring station
By soundlevelmeter.review editors, practising acousticians. Published . Neutral by policy: no brand pays for placement.
A noise monitoring station is bought when a sound level meter on a tripod will not do: the measurement lasts weeks or years, the site is remote, or the results must be seen the same day by people who were not there. The specification is therefore less about acoustics, which the meter inside takes care of, and more about engineering the instrument into a system that runs without anyone standing beside it. This guide sets out the headings that belong in a specification, in the order they usually decide the purchase.
The meter inside
Specify the sound level meter to IEC 61672-1 class 1, with 1/3- octave filters to IEC 61260-1 class 1 if spectra are needed for tonality or source identification. Ask the manufacturer to state the class with the outdoor microphone kit fitted: the windscreen, rain cover and bird spike alter the frequency response, and a class 1 meter is only a class 1 station if the kit has been tested with it. Where measurements will have legal effect in a country with a verification scheme, the meter and kit together must hold pattern approval. Several stations in the database are built around a handheld meter that is also sold separately; the station page links to it.
Autonomy and power
Autonomy is the number of days the station runs without a site visit. It is set by the power source and the consumption of meter, modem, heating and any sensors. The options, roughly in order of cost and complexity:
- Mains power with a battery to ride through outages. The simplest where a socket exists; requires an electrician and often a permit.
- Exchangeable batteries sized for one to four weeks. Requires regular visits; every visit is a chance to check the calibration as well.
- Solar with a battery buffer. Autonomy becomes effectively unlimited if the panel is sized for the darkest month and the site is unshaded; panels attract attention and theft.
- Fuel cell or generator for large construction or mining sites where other equipment is already powered that way.
Datasheet autonomy figures are measured under one set of conditions; ask whether they include the modem, audio recording and the microphone heater, and at what temperature.
Communications
Cellular (4G LTE, with 5G or LTE-M appearing) is the default. Ethernet suits permanent installations on a site network; Wi-Fi is rarely dependable outdoors; satellite is the fallback for remote sites. The specification should state the upload interval, what is uploaded (summary values, time history, spectra, audio) and what happens during an outage: a station that buffers locally and back-fills loses nothing, one that streams loses the gap. Supplier-provided SIM plans are convenient but tie the station to one network and one subscription.
Weatherproofing and the outdoor microphone kit
The enclosure should carry an IP rating to IEC 60529 of at least IP65 for the electronics, with the operating temperature range stated for the whole station rather than for the meter alone. The outdoor microphone kit is where most long-term failures start, so it deserves its own lines in the specification:
| Item | Why it matters | What to ask for |
|---|---|---|
| Windscreen | Reduces wind-induced noise, which otherwise sets the floor of night-time measurements | Published insertion-loss correction, applied automatically or documented |
| Rain protection and bird spike | Rain on the diaphragm and birds on the windscreen are the two commonest data artefacts | Design tested for class 1 with the kit fitted; replacement foam available |
| Microphone and preamplifier | Must hold calibration through humidity, condensation and temperature cycling | Prepolarised or externally polarised ½-inch microphone with heater or dehumidifier option |
| Remote check | Detects a drifting or failed microphone between visits | Electrostatic actuator or charge injection check, scheduled daily, with alarm on deviation |
| Mounting | Microphone height and distance from reflecting surfaces are set by the measurement standard | Mast or tripod to the required height (often 1.5 m or 4 m), with cable routing and lightning earth |
Remote calibration checks
Unattended data are only defensible if the instrument can be shown to have been working throughout. Two techniques are used. An electrostatic actuator fitted over the diaphragm applies a known electrostatic force and so tests the microphone itself. Charge injection calibration injects a known signal at the microphone terminals and compares the chain’s response with the value stored at installation; a change indicates a fault in the microphone, cable or preamplifier. Neither replaces the acoustic calibrator: both are stability checks referenced to a field calibration done by a person at installation and at the intervals the measurement standard requires. Specify that the check runs automatically, that results are logged with the measurement data, and that a deviation beyond a set tolerance raises an alarm. See the calibration guide for the laboratory side.
Software and cloud platforms
Most stations are sold with a web platform that displays levels, spectra and audio, sends alerts and produces reports. Evaluate it as carefully as the hardware: whether it is included or a subscription; what happens to display and alerts if the subscription lapses; whether there is an API; how many users and projects are included. Ask for a trial login with real data before signing.
Data ownership and retention
Write into the contract that the measurement data belong to you, that raw time histories and spectra can be exported in an open format (CSV or a documented binary) at any time, that data remain downloadable for a stated period after the subscription ends, and where the servers are located, which matters for public-sector clients and for personal data in audio recordings. Audio recording of a public place may engage privacy law; many platforms offer short, triggered recordings with a pre-set maximum duration for that reason.
Specification checklist
- Meter: IEC 61672-1 class 1 stated with outdoor kit; 1/3-octave filters IEC 61260-1 class 1 if required; pattern approval if legally required.
- Autonomy: power source, days of autonomy at stated temperature with modem and audio on.
- Communications: network, upload interval, local buffering, SIM arrangement.
- Environment: IP rating, operating temperature of the complete station, mounting height.
- Verification: remote calibration check method, schedule, alarm; acoustic calibrator supplied.
- Software: included functions, subscription terms, API, users, alerting.
- Data: ownership, export format, retention, server location, audio privacy settings.
- Support: warranty, service centre, spare microphone kits, loan unit.
The category table shows autonomy, protection rating and connectivity for every station in the database, and the comparison tool puts up to four side by side.
Frequently asked questions
- Does a noise monitoring station have to be class 1?
- For environmental compliance, planning conditions and complaint investigation, yes in almost every jurisdiction, and some countries additionally require pattern approval of the meter inside. Class 2 kits exist for screening. Whatever the class, it should be stated for the complete outdoor configuration, because the microphone kit changes the frequency response.
- How long will a station run on batteries?
- Anything from two days to several weeks, depending on the meter, the modem's duty cycle, logging and audio settings, battery capacity and temperature. Treat the datasheet figure as the result of one set of conditions and ask which. Solar panels extend autonomy but must be sized for the darkest month.
- What is a remote calibration check?
- A way of verifying the microphone and signal chain without visiting the site. An electrostatic actuator applies a known force to the diaphragm; charge injection compares the chain's response with a reference stored at installation. Both are stability checks, not traceable calibrations; the station must still be checked with an acoustic calibrator at installation and at intervals.
- Can I use a handheld sound level meter in a weatherproof box instead?
- Yes, and several manufacturers sell exactly that as an outdoor kit. It works well for attended surveys of a few weeks. For permanent installations a purpose-built station is usually better value once power management, modem integration and remote diagnostics are added up.
- Who owns the measurement data?
- Whatever the contract says, which is why it should be written down. Ask whether raw time histories and audio are stored on the station as well as in the cloud, in what format they export, whether they remain accessible if the subscription lapses, and where the servers are.
Related tables: Noise monitoring stations. Terms are defined in the glossary; the standards referred to are explained under Standards.
More guides
- Class 1 vs class 2 sound level meters · IEC 61672-1 tolerances, what the classes do and do not say, and where each is typically required.
- Sound level meter calibration and verification · Field calibration vs laboratory calibration, IEC 61672-3, ISO 17025, intervals, reading a certificate.
- Understanding sound level meter specifications · Reading a datasheet: ranges, noise floor, weightings, filters, FFT, logging, and what is omitted.