Laboratory notes
What gets written up here
- Mounting effects. How much a result moves between Type A, Type E-200 and Type J for the same specimen — the single largest source of disagreement between a laboratory figure and site performance.
- Specimen variability. How much two samples of the same product, from the same batch, actually differ. It is usually more than the difference a customer is trying to prove.
- Standard comparisons. Where ISO and ASTM routes give different answers for the same material, and why the difference is real rather than an error.
- Calibration drift. What we see across instruments returning year after year — which components move, how fast, and in which direction.
- Installation faults. What a mounting error looks like in the data, and how a small perimeter leak flatters or ruins a sound insulation result.
Nothing identifies a client
Notes are published anonymised by product category and construction, never by brand, and never with a result that could be traced to a specific client's product without their written permission. Confidentiality is a condition of accreditation, not a courtesy.
We are not going to publish another article explaining what sound absorption is. Anyone can get that answer in seconds now. What cannot be produced without doing the physical work is what we actually observe in the rooms — so that is what goes here.
The air gap changes your absorption more than the material does
The same absorber measured Type A and Type E-200 gives two very different low-frequency curves. Both are correct. Only one matches how your product is installed.
ASTM or ISO for transmission loss testing in Thailand?
STC and Rw are not the same number and do not convert reliably. Which one you need is decided by your destination market, not by the laboratory.
What calibration drift actually looks like
Instruments rarely fail suddenly. They drift quietly, and every measurement made in between is wrong by an amount nobody notices.