How often should I calibrate my SPL meter?

Field calibration should be performed before and after every measurement session. Laboratory calibration by an accredited facility should occur annually or per manufacturer recommendation. IEC 61672-1 requires periodic verification to maintain Class 1 or Class 2 compliance.

What is the difference between 94 dB and 114 dB calibrators?

Both produce known SPL at 1 kHz. The 94 dB calibrator is quieter and more practical for field use. The 114 dB calibrator provides higher level for checking meter linearity. Pistonphones produce 124 dB and are used in laboratory environments. Choose based on your meter's calibration procedure.

Can I calibrate an SPL meter without a calibrator?

Without an acoustic calibrator, you cannot achieve traceable calibration. You can do a rough check by comparing your meter against a known-calibrated reference meter measuring the same source, but this transfers any errors from the reference meter and is not acceptable for regulatory measurements.

Why does my SPL meter reading drift during measurement?

Common causes include temperature change affecting microphone sensitivity, battery voltage drop, condensation on the diaphragm, and electronic component aging. If drift exceeds 0.5 dB during a session, the measurements should be repeated after re-calibration.

Does humidity affect SPL meter calibration?

High humidity can affect microphone diaphragm stiffness and acoustic impedance. Most calibrators specify valid operating conditions (typically 23 degrees C, 50 percent RH). For high-precision work, correction factors may apply. For field measurements, humidity effects are typically within the meter's tolerance.

How often should I calibrate my SPL meter?

Field calibration should be performed before and after every measurement session. Laboratory calibration by an accredited facility should occur annually or per manufacturer recommendation. IEC 61672-1 requires periodic verification to maintain Class 1 or Class 2 compliance.

What is the difference between 94 dB and 114 dB calibrators?

Both produce known SPL at 1 kHz. The 94 dB calibrator is quieter and more practical for field use. The 114 dB calibrator provides higher level for checking meter linearity. Pistonphones produce 124 dB and are used in laboratory environments. Choose based on your meter's calibration procedure.

Can I calibrate an SPL meter without a calibrator?

Without an acoustic calibrator, you cannot achieve traceable calibration. You can do a rough check by comparing your meter against a known-calibrated reference meter measuring the same source, but this transfers any errors from the reference meter and is not acceptable for regulatory measurements.

Why does my SPL meter reading drift during measurement?

Common causes include temperature change affecting microphone sensitivity, battery voltage drop, condensation on the diaphragm, and electronic component aging. If drift exceeds 0.5 dB during a session, the measurements should be repeated after re-calibration.

Does humidity affect SPL meter calibration?

High humidity can affect microphone diaphragm stiffness and acoustic impedance. Most calibrators specify valid operating conditions (typically 23 degrees C, 50 percent RH). For high-precision work, correction factors may apply. For field measurements, humidity effects are typically within the meter's tolerance.

How to Calibrate an SPL Meter

6 steps15-20 min readUpdated 2026-03-20

Quick Answer

Calibrating an SPL meter means verifying its measurement accuracy against a known reference source, typically a pistonphone or electronic acoustic calibrator that produces a precise sound pressure level at a specific frequency. Regular calibration ensures your noise measurements meet the accuracy requirements of IEC 61672-1 and produce legally defensible, scientifically valid data.

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Equipment Needed

✓Acoustic calibrator (IEC 60942 Class 1 or Class 2)
✓SPL meter or measurement microphone to calibrate
✓SonaVyx SPL Meter tool for phone calibration
✓Calibration log sheet or digital record
✓Adapter rings for different microphone sizes (if needed)

Step-by-Step Guide

Select an Acoustic Calibrator

Use a Class 1 acoustic calibrator per IEC 60942 that produces a known SPL, typically 94 dB or 114 dB at 1 kHz. The calibrator must be compatible with your microphone capsule size (typically 1/2-inch or 1/4-inch). Pistonphone calibrators (produce 124 dB) are laboratory-grade. Electronic calibrators (94 or 114 dB) are more practical for field use. The calibrator itself should be verified annually by an accredited calibration laboratory with traceable certification.

Check Calibrator Battery and Condition

Verify the calibrator battery level before use. Low battery voltage can shift the output level by 0.5 to 1.0 dB. Inspect the calibrator cavity for debris, moisture, or physical damage. If the calibrator has been dropped, it should be returned for re-certification. Note the calibrator serial number and certification expiry date. These details are required for calibration records and audit trails.

Prepare the SPL Meter

Set the meter to the calibration frequency weighting, usually A-weighting or Z-weighting (unweighted), depending on the calibrator specification. Select Slow time weighting for stable readings. Remove any windscreen from the microphone. If the meter has been stored in extreme temperatures, allow 15 minutes for thermal stabilization. Note the ambient temperature and humidity, as these affect the reference conditions and may require small corrections for high-precision work.

Apply Calibrator to Microphone

Carefully place the calibrator over the microphone capsule, ensuring a snug, airtight seal. The calibrator cavity must completely enclose the microphone diaphragm. Any air leak reduces the calibration level and introduces error. Hold the calibrator steady and turn it on. Wait 10 seconds for the sound field to stabilize. The meter should display a level close to the calibrator's rated output. For SonaVyx, navigate to SPL Meter settings and tap the calibration button.

Adjust Calibration Offset

If the meter reading differs from the calibrator's rated level, apply a correction offset. For a 94 dB calibrator, if the meter reads 92.5 dB, the correction offset is +1.5 dB. In SonaVyx, enter the known calibrator level and the tool automatically calculates and applies the offset. For dedicated SPL meters, use the calibration potentiometer or digital adjustment to match the displayed level to the calibrator output. The corrected reading should match within plus or minus 0.3 dB.

Record and Verify

Document the calibration: date, time, calibrator model and serial number, calibrator certification expiry, ambient conditions, pre-calibration reading, applied offset, and post-calibration reading. Verify the calibration at the end of each measurement session by re-applying the calibrator and confirming the level has not drifted. IEC 61672-1 requires that drift during a measurement session be less than 0.5 dB for the measurements to be valid.

Why Calibration Matters

An uncalibrated SPL meter can produce readings that are several dB off, which may seem small but has significant consequences. In occupational noise exposure assessment, a 3 dB error in TWA can mean the difference between compliance and violation. In environmental noise disputes, readings that cannot be traced to a calibration standard are inadmissible. Regular calibration ensures your measurements are accurate, repeatable, and legally defensible.

Calibration Frequency and Uncertainty

Most acoustic calibrators produce a 1 kHz tone because this is the reference frequency for A, C, and Z weighting networks (all three are within 0 dB of unity at 1 kHz). The calibration verifies the complete signal chain at this single frequency. Full-spectrum verification requires an electrostatic actuator and is performed during laboratory calibration. Field calibration at 1 kHz is considered sufficient for operational accuracy per IEC 61672-1 when combined with periodic laboratory calibration.

Calibrating Phone-Based SPL Meters

Phone microphones require calibration because MEMS microphone sensitivity varies by device model and individual unit. SonaVyx provides a calibration offset feature: play a known SPL level from a calibrator or reference source, then enter the known level in the calibration dialog. The app applies a constant offset to all subsequent readings. While this single-point calibration does not correct for frequency-dependent errors, it significantly improves absolute level accuracy, typically bringing phone measurements within plus or minus 2 dB of a calibrated Class 2 meter.

Common Mistakes to Avoid

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Using an expired calibrator without current traceable certification, which invalidates the calibration

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Not ensuring an airtight seal between the calibrator and microphone, causing readings 1 to 5 dB low

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Forgetting to remove the windscreen before calibration, which attenuates the calibrator output

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Calibrating only at the start and not verifying at the end of the measurement session

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Applying the wrong calibrator level (confusing 94 dB with 114 dB, a 20 dB error)

Applicable Standards

Standard	Clause	Relevance
IEC 61672-1:2013	Clause 5.4.3	Field calibration requirements for sound level meters
IEC 60942:2017	Clause 4	Sound calibrator specifications and classifications
ANSI S1.4-2014	Clause 5	Calibration requirements for sound level meters

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