Anechoic and hemi-anechoic chamber
A qualified free-field room: sound leaves the source and does not come back. That is what makes sound power, loudspeaker response and product noise measurements comparable between laboratories instead of being descriptions of a room.
What "qualified" means, and why it is not a marketing word
Any room lined with foam wedges can be called anechoic. Whether it behaves as a free field is a separate question, and it is answered by test rather than by appearance. ISO 26101-1 sets out how: sound pressure is measured along paths away from a source and compared against the inverse square law that would hold in a true free field. Where the measured decay departs from it by more than a stated tolerance, that part of the room is not qualified and cannot be used for the measurement.
The practical consequence is that a qualified room has a defined measurement volume and a defined frequency range, both established by test, not by the size of the wedges. This is why sound power to ISO 3745 can be claimed as precision grade in some rooms and not in others that look identical.
What we can test
- Product size
- Confirmed against your product dimensions on enquiry
- Sound power grade
- ISO 3745 precision grade 1
- Free-field qualification
- ISO 26101-1 — qualified measurement surface confirmed by test
- Background noise
- At least 10 dB below the lowest reported band, per ISO 3745
- Services
- Sound power, loudspeaker and electroacoustic measurement, product noise
Chamber dimensions are issued with your quotation
We publish the product envelope, because you need it to know whether your product fits. Internal chamber dimensions, cut-off frequency and the measured noise floor are provided with your quotation and stated on every test report.