Environmental Sound Level Meter Uses
Sound level meters are vital tools in numerous fields.
A Sound Level Meter (SLM) is an instrument (commonly hand-held) that is designed to measure sound levels in a standardized way.
Sound level meters are used to measure and manage noise from a variety of sources, including industrial plants, road and rail traffic, and construction work. They ensure compliance with local noise regulations in environmental noise monitoring and protect workers’ hearing in workplace noise monitoring. Additionally, they are invaluable in research for measuring sound levels across different environments.
Sound level meters are the most commonly used tools for noise measurement and compliance.
Whether evaluating workplace noise, assessing equipment performance, or conducting environmental surveys, the right tool delivers consistent, defensible results.
Components of a Sound Level Meter
A sound level meter comprises a microphone, a preamplifier, signal processing, and a display. The microphone converts the sound signal to an equivalent electrical signal. The electrical signal produced by the microphone is at a very low level, so it is made stronger by a preamplifier before it is processed by the main processor.
Key Features of Modern Sound Level Meters
Modern sound level meters come with advanced features. Look for models with selectable frequency weightings (A, C, or Z) for precise measurements tailored to different applications. Data logging capabilities enable continuous monitoring and recording of sound levels over time. Wireless and cloud connectivity, such as WiFi, add convenience for remote monitoring.
Understanding Sound Measurement Parameters
The display shows the sound level in decibels, typically with a descriptor showing the selected combination of time and frequency-weighting (eg; LAeq or LCpeak).
Time weighting specifies how the SLM reacts to changes in sound pressure. The analyzer applies Fast, Slow, and Impulse (or ‘F’, ‘S’ and ‘I’) time weightings, which are the required weightings according to most international and national standards and guidelines.
The signal is processed through the weighting filters, and the resulting sound pressure level is displayed in decibels (dB) referenced to 20 μPa on the analyzer’s screen.
Frequency Weighting and Analysis
Frequency weighting adjusts how the sound level meter responds to different sound frequencies. This is necessary because the human ear’s sensitivity to sound varies according to the sound’s frequency.
A-weighting adjusts a signal in a way that resembles the human ear’s response at medium-range levels. It is based on the 40 dB equal loudness curve. A-weighting is required for nearly all environmental and workplace noise measurements and is specified in international and national standards and guidelines.
The response of the human ear varies with the sound level. C frequency weighting corresponds to the 100 dB equal loudness curve, that is to say, the human ear’s response at fairly high sound levels. C-weighting is mainly used when assessing peak values of high sound pressure levels.
Today, the A-weighting network is the most widely used frequency weighting.
When more detailed information about a complex sound is required, the frequency range can be divided up into sections or bands. This is done with electronic or digital filters, which reject all sound with frequencies outside the selected band.
An octave is a frequency band where the highest frequency is twice the lowest frequency. For example, an octave filter with a centre frequency of 1 kHz admits frequencies between 707 and 1414 Hz but rejects all others. (The name octave stems from the fact that an octave covers eight notes of the diatonic musical scale).
The process of thus dividing a complex sound is termed frequency analysis and the results are presented on a chart called a spectrogram.
The RMS is a special kind of mathematical average value.
Leq: The Averaged Sound Level Parameter
Assessing a fluctuating noise level means getting a value for a level that is, in simple terms, the average level. The ‘equivalent continuous sound level’, Leq, is known around the world as the essential averaged parameter.
Leq is the level that, had it been a steady level during the measurement period, would represent the amount of energy present in the measured, fluctuating sound pressure level. It is not a direct measure of annoyance, though extensive research has shown that Leq correlates well with annoyance.
Leq can be measured directly with most professional SLM’s (sometimes called an integrating sound level meter).
Calibration and Best Practices
Calibration is an adjustment of your SLM to measure and display correct values. While you are unlikely to ever experience a large drift or change in sensitivity with the SLM, it is nevertheless, good practice to regularly check the calibration of your SLM, normally before and after each set of measurements. This is best done by placing a portable acoustic calibrator directly over the microphone.
Conducting sound measurements requires a sound level meter of course, but the sound level meter itself is only one of the many things you need to remember when on a measurement job.
International Standards
International standards are important either because they are used directly or because they provide inspiration or reference for national standards. The International Organization for Standardization (ISO) deals primarily with a methodology to ensure that procedures are defined to enable the comparison of results.
“IEC 61672 - Electroacoustics - Sound level meters” is the current international standard that sound level meters should meet to satisfy most modern regulations. Part 2: Pattern evaluation tests - provides details of the tests necessary to verify conformance to all mandatory specifications given in IEC 61672-1.
Choosing the Right Sound Level Meter
Choosing the right sound level meter depends on your specific requirements. Are you monitoring environmental noise, occupational noise, or conducting scientific studies?
Consider the accuracy, cost, datalogging, recording time, and additional features like weather-resistance or wireless connectivity.
Understanding your specific needs is key to choosing the right sound level meter.
Sound level meters vary based on functionality and application. Basic models measure instantaneous sound pressure levels while integrating models provide levels averaged over time (LEQ). Data logging meters store measurements for later analysis.
Sound level meters are primarily classified as Class 1 and Class 2. Class 1 offers high precision and a wide frequency range, making them suitable for professional and research purposes. Class 2 have slightly wider tolerances and are aimed at less demanding applications.
Here are the most important factors to consider when choosing a noise meter:
- Accuracy and Class Rating (Class 1 vs. Class 2). Class 1 meters provide the highest precision, meeting IEC 61672-1 standards with ±1 dB accuracy across a broad frequency range. They’re ideal for regulatory testing, research, and environmental surveys. Class 2 meters, while slightly less precise, are rugged and cost-effective for general industrial monitoring.
- Measurement Type. Determine whether you need spot measurements, time-averaged (integrating) readings, or continuous logging. Integrating and logging meters record noise trends over time, offering deeper insights into fluctuating sound environments.
- Environmental Conditions. Consider the measurement environment. High temperatures, humidity, or strong air movement can affect readings. Look for models with environmental compensation or weatherproof accessories when working outdoors.
- Frequency and Time Weighting Options. Choose meters that support A, C, and Z frequency weighting, along with Fast, Slow, and Impulse time responses. These functions ensure data meets regulatory requirements and accurately reflects how humans perceive noise.
- Connectivity and Data Management. Many digital sound level meters include USB or Bluetooth connectivity for easy data transfer. Software integration allows automatic report generation and trend analysis-key for compliance audits and ongoing monitoring programs.
- Durability and Intrinsic Safety. For environments such as refineries or chemical plants, intrinsically safe designs prevent ignition risks. Rugged housings and shock-resistant cases protect meters from vibration and dust exposure in harsh field conditions.
When in doubt, match the tool to the task. A high-accuracy Class 1 sound level meter suits formal testing and environmental impact studies, while a compact Class 2 digital meter is often sufficient for daily workplace monitoring.
Sound Level Meter Selection Chart
Select a sound level meter based on your objective, accuracy requirements, and environment.
If your goal is regulatory or environmental compliance, choose a Class 1 or integrating sound level meter.
For routine workplace monitoring, a Class 2 or logging sound level meter usually provides sufficient accuracy and durability.
This chart summarizes the main sound level meter types to help you identify the right solution for your application.
| Type | Accuracy | Measurement Purpose | Duration / Mobility | Data Output | Environment | Typical Use Cases |
|---|---|---|---|---|---|---|
| Class 1 Sound Level Meter | ±1 dB, IEC 61672-1 Class 1 | High-precision measurements for compliance and research | Tripod or handheld; stationary use preferred | Time-history, frequency analysis, Leq, statistical data | Labs, outdoors, environmental studies | Regulatory testing, acoustic surveys, baseline monitoring |
| Class 2 Sound Level Meter | ±2 dB, IEC 61672-1 Class 2 | General-purpose workplace and equipment noise checks | Portable, handheld | Instantaneous or averaged SPL readings | Industrial facilities, maintenance shops | Routine noise surveys, maintenance inspections, PPE validation |
| Integrating Sound Level Meter | Same class tolerances as base model (Class 1 or 2) | Measures total sound energy over time (Leq) | Short-term or shift-based | Average exposure, TWA, peak and trend analysis | Dynamic environments, process areas | Shift-based exposure studies, fluctuating noise profiles |
| Logging / Data-Recording Sound Level Meter | Matches base class accuracy | Continuous or periodic logging with timestamps | Stationary or semi-portable | Time-stamped logs, exportable CSV/JSON | 24/7 operations, compliance sites | Environmental audits, community impact assessments, long-term monitoring |
| Intrinsically Safe / Ruggedized Model | Class 1 or 2 with IS certification | Noise monitoring in hazardous or high-vibration areas | Handheld or wearable | Standard SPL or logged data | Oil & gas, chemical, or mining operations | Hazardous-area safety checks, confined space monitoring |
Selection Criteria Checklist
Use this checklist to identify the right sound level meter for your work environment and regulatory obligations.
- Accuracy & class rating. Confirm Class 1 (±1 dB) or Class 2 (±2 dB) tolerance per IEC 61672-1.
- Measurement functions. Spot, integrating (Leq), or logging capability depending on task duration.
- Frequency & time weighting. A/C/Z frequency and Fast/Slow/Impulse response options to meet regulations.
- Calibration & QA/QC. Field calibration, traceable reference checks, and maintenance intervals.
- Data & connectivity. USB/Bluetooth export, PC integration, automated reporting tools.
- Durability & safety rating. IP protection, drop resistance, and intrinsic safety certification where needed.
- Power & runtime. Battery life, external power options, and charging compatibility for long deployments.
Sound Level Meter Apps
Sound meter apps on smartphones can provide a rough estimate of noise levels but lack the precision and reliability of dedicated sound level meters. Factors like shape, size, microphone quality and calibration, and environmental conditions can affect their accuracy. In addition, a smart phone usually cannot be left on location for extended periods of time. For professional and regulatory purposes, it’s best to use a calibrated sound level meter.
Time to Invest in a Sound Level Meter?
Having the right tool for the job makes you efficient - and that is good business.
For short-term (up to a few weeks) operation, choose the simple low-cost NSRT_mk4. For operations spanning multiple months, and to avoid having to dispatch personnel to the location(s), choose the NSRTW_mk4 or NSRTW_mk4 with cloud.