A technical guide to sound level calibration

Accurate acoustic measurement is a major quality assurance aspect across multiple industries from manufacturing to environmental monitoring. Yet, ensuring this precision hinges on reliable, standards-compliant calibration rather than the choice of instrumentation. 

Because of this, engineers need a clear understanding of the tools and techniques used in sound level calibration to ensure clarity and dependable results without diving too deep into the technicalities.

Why sound level calibration matters

In environments where noise limits or acoustic signatures are critical, even minor deviations in sound level meter readings can lead to significant consequences like product non-compliance and regulatory penalties. Calibration is required to eliminate this risk by ensuring instruments measure accurately and consistently over time, even in the face of environmental and mechanical wear.

The core instruments in sound level calibration

At the heart of sound level calibration are a few key components which together form the basis for assessing whether your sound measurement equipment is functioning within acceptable tolerances.

• Sound level meters (SLMs): Devices that measure the intensity of sound in decibels (dB), used widely in industrial, environmental and workplace assessments.
  
  
• Acoustic calibrators: Portable devices that emit a known sound pressure level at a defined frequency, commonly 94 dB at 1 kHz, to verify and adjust the response of SLMs.
  
  
• Microphones: Precision microphones are typically used with SLMs and must also be verified for frequency response and sensitivity.

Sound level calibration is typically carried out in two stages. 

• Field calibration: Performed before and after use on-site using an acoustic calibrator. This is a quick check to ensure no drift or fault has occurred during use. 
  
  
• Laboratory calibration: A more thorough process which is usually conducted annually, which tests the instrument's performance across a range of frequencies and sound levels using traceable reference equipment under controlled conditions.

Field calibration helps ensure day-to-day reliability, but only a laboratory calibration can verify full compliance with standards like IEC 61672 or ISO 17025 which are essential for formal reporting or legal compliance.

Where accredited laboratory calibration is necessary 

Several operational and environmental factors can affect the accuracy of acoustic measurements.

• Temperature and humidity: These can impact microphone sensitivity and sound wave propagation.
  
  
• Barometric pressure: Especially at high altitudes, this can influence calibrator output and sound levels.
  
  
• Mechanical damage or wear: Even minor impacts can misalign internal components, affecting accuracy.

This is why regular and especially laboratory-based calibration is essential for any business reliant on acoustic data. These services ensure testing is performed in the right environments where accuracy and precision are guaranteed. 

A calibration partner you can trust

Accurate sound level measurement is essential for ensuring compliance and product quality in noise-sensitive environments. Without regular, reliable calibration, even the most advanced sound level meters can drift out of tolerance, leading to costly inaccuracies and potential compliance risks.

At DM Systems & Test, we specialise in UKAS-accredited calibration that meets the highest standards of traceability and precision. Our expert mobile technicians deliver laboratory-grade accuracy on-site, eliminating downtime and ensuring your equipment operates within spec, every time. 

For a deeper dive into what to look for when choosing a calibration partner, download our full technical guide.