Accreditation and traceability

Three calibration services are accredited, in the field of Acoustics. Calibration and measurement capabilities (CMCs) are expressed as an expanded uncertainty (±) at a level of confidence of approximately 95%.

Our accreditation covers calibration in the field of Acoustics. It does not cover every measurement this laboratory is capable of making, and we will not imply that it does. A laboratory that presents its whole service list as accredited is either careless or overstating, and in a tender dispute that is the first thing an opposing party will go after.

So every service page on this site carries one of three labels. Accredited means the measurement falls inside the scope document above. Traceable means the measurement is made with equipment whose calibration is traceable to national standards, but the method itself is outside our accredited scope. R&D measurement means the work is exploratory or bespoke and is not offered as a conformity statement at all.

Every result we issue carries an uncertainty. That is not a weakness of the measurement, it is the measurement being described properly, and a report without one is incomplete.

It also has a practical consequence most laboratories prefer not to discuss. Published inter-laboratory studies find that the same absorption specimen measured in different accredited reverberation rooms can differ by up to about 0.15 in absorption coefficient at individual frequencies and around 0.08 in NRC, with inherent inter-laboratory uncertainty near ±0.10. That is larger than most of the product differences people use these numbers to argue about.

The practical advice that follows is simple: when you are comparing your product against last year's version, or against a competitor, have both measured at the same laboratory in the same configuration. Comparing a number from us against a number from somewhere else is comparing two things that were never designed to be compared.