What Is a Sound Level Meter?
A sound level meter is a handheld device with a sensitive condenser microphone that turns minute air-pressure changes from sound waves into an electrical signal and shows the resulting level in decibels. Commonly called a sound pressure level (SPL) meter, it follows IEC 61672 Class 1 or Class 2 requirements, so its readings are traceable and legally defensible. Inside the device, the circuitry applies standard A, C, or Z frequency weightings and fast or slow time weightings, so numbers match how our ears judge loudness in different situations.
With those features, a professional sound level meter gives clear, real-time SPL data that helps check workplace exposure limits, community noise rules, or loudspeaker tuning. Whether you are surveying a factory floor or balancing a home studio, using a professional sound level meter keeps the guesswork out of noise measurements and lets you act on solid evidence.
What Is Sound Pressure and SPL?
Sound Pressure (p)
Sound pressure (p) is the tiny rise or fall in air pressure that a sound wave adds to the steady atmospheric pressure around us. Since it is a form of pressure, it is measured in Pascals (Pa). Audible sounds span 20 µPa—the threshold of hearing—to 20 Pa, where discomfort begins.
From Pascals to decibels (SPL)
To shrink that huge numeric range, we convert Pascals to decibels with the equation SPL = 20 × log10(p / p ref). The reference pressure p ref in the air is fixed at 20 µPa, matching the quietest tone an average ear can detect. Meanwhile, a professional sound level meter does this math instantly, so you see one convenient dB value instead of juggling large Pascal numbers.
Why SPL in dB Matters
The ear judges loudness on a logarithmic scale, so equal steps in dB track our perception better than equal steps in Pascals. That’s why safety guides flag 70 dB as “safe” for long listening and why workplace rules need action at 85 dB averaged over an eight-hour shift. Using dB also lets a professional sound level meter report levels in the units that health and legal standards specify.
What Is a Normal Sound Level?
WHO’s Definition of Normal Sound Levels
The WHO states that “background noise level should not exceed 35 dBA” in learning spaces and similar indoor areas, marking this as the normal limit for everyday environments.
Everyday Sound Examples
- Whisper – 30 dB
- Quiet library – 35 dB
- Normal conversation – 60 dB
- Vacuum cleaner – 70 dB
- Busy street traffic – 85 dB
- Lawnmower – 90 dB
- Motorcycle – 95 dB
- Rock concert – 105 dB
- Jet take-off – 140 dB
Remember, a professional sound level meter can confirm that jump.
Health Impacts of Excessive Noise
Levels above 85 dB can damage hearing over time. Furthermore, chronic noise raises stress hormones, disrupts sleep, and brings about fatigue. That’s why checking your surroundings with a professional sound level meter lets you spot risky peaks early and act accordingly.
Types of Sound Level Meters
IEC 60942:2017 / IEC 61672-1 Classes
Professional sound level meters are divided into accuracy classes and processing types. Here’s how they differ:
- Class 1 vs. Class 2 Accuracy
- Class 1: Must remain within ±0.5 dB under reference conditions (e.g., ST-12D). Used in compliance-grade applications such as environmental impact reports, building acoustics, and legal evidence.
- Class 2: Allows up to ±1.0 dB variation. Often used for general surveys or less critical checks.
- Processing Methods (IEC 61672-1)
- Standard RMS (Conventional) Meter: Uses exponential averaging with Fast, Slow, or Impulse time constants. Provides quick, momentary dB readings.
- Integrating Meter: Sums squared, frequency-weighted pressure over time to deliver energy-based metrics such as Leq and SEL.
- Integrating-Averaging Meter: Builds on the integrating meter by adding continuous averaging, logging Leq across the full survey while still displaying real-time SPL data.
- Typical Usage Scenarios
- Standard RMS Meter: Ideal for walk-through checks, sound system setup, or quick community spot checks where only the current dB value matters.
- Integrating / Integrating-Averaging Meter: Required for workplace compliance studies (per ISO 9612) to capture daily dose, peaks, and time history.
- Class 1 Integrating Meters: Essential for environmental impact statements, as they record detailed metrics like night-time Leq, L10, L90, and octave-band data.
Industrial Noise Level Monitoring Equipment Comparison
Compare different types of professional sound level meters and dosimeters to find the right solution for your industrial noise monitoring needs.
| Model | Type / Standard | Measurement Range | Key Features | Best For |
| ST-12D Class 1 Sound Level Meter | Class 1 (IEC 61672-1: 2013) | 25 to 140 dB (143 dB C Peak) | – Class 1 precision – Measures Leq with selectable weightings (A/C/Z) – Optional 1/1 and 1/3 octave band analysis-filters for frequency analysis – Audio recording: .wav / .mp3 | Workplace noise surveys, environmental impact assessments, precision SPL measurement |
| ST-15D Class 1 Sound Analyzer | Class 1 (IEC-61672-2014) | 20 dB–142 dB | – 10 Hz–20 kHz frequency range – Optional 1/3 octave analyzer – Data logging & recording (optional) – Measures & displays Leq – GPS function for geo-stamped surveys | Environmental noise mapping, acoustics research, compliance documentation |
| ST-591 Noise Dosimeter | Class 2 (IEC 61672-1:2013) | 54 db-142 dB (A); 54 db-142 dB (C); 57 dB-142 dB (Z); 71 db-145 dBC (C peak) | – OSHA / MSHA / DOD / ACGIH / ISO compliant – 20 Hz-12.5 kHz frequency range – Measurement modes: sound exposure, integral, statistics, 1/1 & 1/3 OCT analysis – Dual noise threshold profiles – Audio recording: . wav | Personal noise exposure monitoring, full-shift worker assessments, OSHA hearing conservation compliance |
How to Monitor Noise Levels in Industrial Environments
Monitoring noise levels is essential for identifying hazardous exposure and protecting workers’ long-term hearing health. A structured approach helps safety managers pinpoint high-risk areas, control excessive noise, and maintain compliance with workplace regulations.
To assess workplace noise accurately, follow these steps:
Process
- Plan the assessment
- Identify work areas, machinery zones, and tasks with potential high noise levels.
- Identify work areas, machinery zones, and tasks with potential high noise levels.
- Use compliant instruments
- Select professional sound level meters or personal noise dosimeters that meet IEC 61672 Class 1/Class 2 or ANSI S1.4 Type 1/Type 2 standards.
- Select professional sound level meters or personal noise dosimeters that meet IEC 61672 Class 1/Class 2 or ANSI S1.4 Type 1/Type 2 standards.
- Conduct area and task-based measurements
- Measure noise around equipment, production lines, fabrication areas, and outdoor worksites.
- Capture both average levels and sudden peaks.
- Record personal exposure when needed
- Attach dosimeters to workers to collect full-shift exposure data.
- Attach dosimeters to workers to collect full-shift exposure data.
- Analyze results and compare with OSHA limits
- Evaluate readings against OSHA’s 85 dBA (8-hour TWA) permissible exposure limit.
- Evaluate readings against OSHA’s 85 dBA (8-hour TWA) permissible exposure limit.
- Take corrective actions
- Implement engineering controls, administrative controls, or hearing protection programs when thresholds are exceeded.
- Implement engineering controls, administrative controls, or hearing protection programs when thresholds are exceeded.
By performing regular noise assessments, organizations can proactively manage noise risks, protect workers’ hearing health, and ensure compliance with national and international occupational noise standards.
ANSI S1.4: Ensuring U.S. Compliance
ANSI S1.4—The U.S. Anchor Standard
ANSI S1.4 spells out how a meter must respond to sound, how it is calibrated, and how its uncertainty is stated. Essentially, it divides instruments into Type 1 for precision tasks and Type 2 for general surveys. Any professional sound level meter sold for regulated work in the United States must meet these tolerances before it can be labeled Type 1 or Type 2.
ANSI S1.4 and IEC 61672-1—Two Sides of the Same Coin
IEC 61672-1 sets identical Class 1 and Class 2 limitations for worldwide usage. In 2014, the United States text adopted the IEC wording almost verbatim, eliminating the old “Atlantic divide.” A professional sound level meter that carries both marks, therefore, satisfies OSHA inspectors at home and accreditation bodies abroad with the same certificate.
2024 ASA Reaffirmation Keeps the Standard Fresh
ASA formally reaffirmed Parts 1-3 of ANSI/ASA S1.4 in February 2024. Such kind of reaffirmation signals that the document remains technically sound and needs no revision, so laboratories and buyers can continue using it without adjustment. What is more, it locks in the standard’s harmonization with IEC 61672-1 for at least another five-year cycle.
OSHA Requirements and Scarlet Tech Compliance
OSHA’s Technical Manual states that only meters conforming to ANSI S1.4 Type 2 or better may be utilized for compliance measurements. The noise-exposure rule at §1910.95 writes the same requirement into its appendices. Along these lines, Scarlet Tech lists “IEC 61672-1 Class 1” on products such as the ST-12D, so a single professional sound level meter can be taken from a U.S. factory floor to an international audit with no extra paperwork.
Which Noise Level Monitors Are OSHA Compliant?
To meet OSHA requirements for workplace noise assessments, instruments must comply with recognized performance standards. OSHA accepts sound measurement devices that meet ANSI S1.4 Type 2 or IEC 61672-1 Class 2 accuracy levels as the minimum threshold for compliance work.
Scarlet Tech’s professional sound level meters exceed these minimum requirements. Both the ST-12D and ST-15D are Class 1 instruments, offering higher precision than what OSHA mandates. This makes them ideal for regulated workplace surveys, industrial noise monitoring, and environmental assessments where accuracy and traceability are essential.
By using meters that surpass OSHA’s baseline standards, organizations gain more reliable data for decision-making and stronger documentation for regulatory audits.
Ready to Take the Next Step?
Choosing the right professional sound level meter ensures your measurements are accurate, compliant, and defensible. Whether you’re managing workplace safety, preparing environmental reports, or fine-tuning acoustics, having the right tool makes all the difference.
Contact Scarlet Tech today to find the professional sound level meter that meets your needs.
