Acoustic and vibration calibration
A measurement is only as good as the instrument that made it. In Thailand, working-environment noise surveys and factory boundary measurements are only defensible if the instrument carries a valid, traceable calibration certificate.
Sound level meters
Measurement microphones
Acoustic calibrators and pistonphones
Noise dosimeters
Accelerometers and vibration meters
Annual calibration plans
Why instruments need periodic calibration in Thailand
Ministerial Regulation B.E. 2559 (2016) on heat, light and sound in the working environment requires employers to control workers’ time-weighted noise exposure, and the Department of Labour Protection and Welfare notification sets the exposure table from 85 dB(A) over 8 hours down to 90 dB(A) over 2 hours 31 minutes. Meeting that obligation means an annual working-environment survey with a Class 1 or Class 2 instrument.
Separately, the Ministry of Industry notification on factory noise (B.E. 2548) and National Environmental Board Notification No. 15 set a 24-hour Leq limit of 70 dB(A) and a maximum of 115 dB(A), with NEB Notification No. 29 (2022) adding the criterion that a source must not exceed background by more than 10 dB(A).
In every one of those cases, the number is only as strong as the calibration certificate behind the instrument that produced it.
What is inside our accredited scope
Three services on this page are accredited under certificate 24-LB0054: sound level meters, sound calibrators and measurement microphones. Dosimeters, vibration transducers, preamplifiers and measurement chains are calibrated traceably but sit outside that scope, and we say so on each page rather than letting the accreditation imply more than it covers. The full scope document is downloadable on the accreditation page.
| Standard | What ALT does with it | Status |
|---|---|---|
| IEC 61672-3 Electroacoustics — Sound level meters — Periodic tests | Our accredited method for periodic testing of Class 1 and Class 2 sound level meters, verifying conformity to the specification in IEC 61672-1. This is the standard behind every legally usable noise measurement in Thailand. | ISO/IEC 17025 accredited |
| IEC 61094-2 cl. 5.3 Measurement microphones — Pressure calibration of laboratory standard microphones | Pressure sensitivity at 250 Hz and 1 kHz. Accredited, with a CMC of 0.15 dB. | ISO/IEC 17025 accredited |
| IEC 61094-6 cl. 5.3 Measurement microphones — Electrostatic actuators for frequency response determination | Frequency response by electrostatic actuator, accredited from 100 Hz to 20 kHz with CMCs from 0.040 dB to 0.55 dB depending on band. | ISO/IEC 17025 accredited |
| IEC 60942 Electroacoustics — Sound calibrators | Accredited calibration of sound calibrators: sound pressure level 70–135 dB, frequency 31.5 Hz–16 kHz, and total distortion plus noise. | ISO/IEC 17025 accredited |
| ISO 16063 series Methods for the calibration of vibration and shock transducers | Accelerometer and vibration meter calibration by comparison against a reference transducer. | Traceable — not in accredited scope |