Sound absorption: in-situ measurement with Sonocat
What problem are we solving?
Laboratory values of a material (reverberation chamber, impedance tube) often differ from how it behaves once installed – the air gap, the frame, the paint and the fabric all have an effect.
We measure sound absorption directly on site – on finished walls, ceilings, linings and plasters – without cutting samples and without damaging the surface.
Standards and status of the measurement
The method is an in-situ point measurement, following the principles of ISO 13472-2.
The measurement is an engineering assessment, and is not accredited. It is used to check, compare and optimise materials. If you need an official test report, see Measurements and diagnostics.
Equipment: What do we use to measure?
We measure with Sonocat (Demcon) – a sound intensity probe. The probe is placed close to the surface, separates the incident from the reflected sound wave, and so the sound absorption coefficient is calculated in situ.
- It is not an acoustic camera – it measures at points.
- Frequency range – from 50 Hz upwards.
- No impedance tube or sample cutting is needed.
Practical use
In-situ measurement is useful for:
- New materials – prototypes made from recycled and natural raw materials, in real conditions.
- Interior elements with unknown properties – curtains, carpets, upholstered furniture, decorative panels.
- Renovation of halls, offices and theatres – how much the existing surfaces absorb and what to add.
- Checking the installation – whether the installed material matches the design specification.
Process and Analysis: What Does the Client Get?
Technical report with:
- sound absorption coefficient α by frequency band – from 50 Hz upwards;
- absorption graph at low, mid and high frequencies;
- single-number rating (αw, NRC) for comparing materials;
- comparison with the design specification;
- recommended measures where needed.
Frequently Asked Questions
Can curved surfaces be measured?
The method is for flat surfaces. With a large radius of curvature the result is acceptable; with a small one it is indicative.
How long does an in-situ measurement take?
It depends on the number of surfaces. For a reliable result, several points are measured on each surface. We confirm the time when you enquire.
Is it suitable for acoustic plasters?
Yes. It is one of the few ways to check on site a material that cannot be cut out for a laboratory test.
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