Acoustic calibrator and pistonphone calibration
Calibrators and pistonphones we calibrate
- Brüel & Kjær (HBK) — 4231 sound calibrator and 4228 pistonphone
- Larson Davis — CAL200 and CAL250
- Rion — NC-74, NC-75
- Norsonic — Nor1251, Nor1256
- Svantek SV 30 and SV 33, Cirrus Research CR:515, CESVA and NTi Audio
We are not an authorised service centre for any of these makers and have no commercial relationship with them. Calibration is performed against the standard, not against a manufacturer's procedure, so the make matters far less than the class of the instrument. If yours is not listed, ask — the list is what we see most, not a limit.
Turnaround
- Standard lead time
- 10 working days from receipt
- Express service
- Available on request, subject to laboratory schedule — quoted at booking
- Loan instrument during calibration
- On request, subject to availability
- Send with the instrument
- Accessories that affect the reading — preamplifier, extension cable, windscreen — and the date of the last calibration
The calibrator is what your field team trusts before every survey. If it has drifted, every measurement made after it is wrong by the same amount, and nobody notices.
- Sound pressure level at the nominal output
- Output frequency
- Total distortion including noise
- Class 1 and Class LS devices
- Stability against the previous certificate
The error that multiplies
Almost every other instrument error affects one measurement. A calibrator error affects all of them. Your field team adjusts the meter to the calibrator at the start of the survey, so whatever offset the calibrator carries is written into every reading taken that day — and, because the same calibrator is used next week, into every reading taken that month.
It is also the failure mode nobody notices, because the field check passes perfectly. The meter agrees with the calibrator; both are wrong together. The only thing that detects it is calibrating the calibrator.
Class matters, and so does the weather
IEC 60942 defines calibrator classes, and a Class 1 sound level meter checked with a Class 2 calibrator is not being checked to Class 1 performance. If your work has to hold up as Class 1, the calibrator has to match.
The second point catches people out in Thailand specifically. Some calibrator designs are sensitive to ambient atmospheric pressure, so a device that is accurate at sea level in a laboratory reads differently at altitude or in unusual pressure conditions. Where that applies, the correction is a real correction, not a rounding detail — and it belongs in your procedure, not in someone's memory.
How often should a calibrator be calibrated?
On the same annual cycle as the meters that depend on it, at minimum. Treat it as the most important instrument you own rather than an accessory, because every other result is referenced to it.
Is calibrator calibration accredited at ALT?
Yes. Sound calibrators to IEC 60942 are one of the three services inside certificate 24-LB0054, alongside sound level meters and measurement microphones.