Acoustical Investigation & Research Organisation Ltd (AIRO) provides measurement and testing of the acoustical properties of materials, constructional elements and products both in AIRO’s purpose-built laboratory at Hemel Hempstead, Hertfordshire and on-site.
AIRO routinely measures the sound insulation of window systems, masonry and lightweight walls, ventilators, floors and roofs together with the sound absorption properties of objects and materials such as office screens and mineral fibre ceiling tiles. AIRO also measures the sound power levels of products such as MVHR (Mechanical Ventilation with Heat Recovery) units.
The organisation has successfully developed methods for more challenging acoustical measurements including very low sound levels from auditoria lighting for a project in Singapore and very high sound insulation facades for a residential project adjacent to an aggregates wharf on the River Thames. Of recent note are laboratory measurement projects to determine the acoustical privacy of modern office privacy pods.
The AIRO laboratory comprises a series of chambers, made structurally independent of each other by being physically separate and mounted on anti-vibration mounts. The chambers are designed to have a diffuse sound environment (uniform throughout the space) by being reverberant, irregularly shaped (to avoid parallel planes) and with additional suspended acoustically reflective panels to further diffuse the sound in the chamber. Undue noise transmission from outside to inside, the chambers is minimised by the heavy masonry construction of the chambers and the chambers are inside a further overall masonry building envelope. Double sets of specialist heavy doors with cam locks onto perimeter seals provide access. Samples are built into the appropriately sized aperture between a pair of chambers for testing their sound insulation or installed or simply placed in a chamber when sound absorption or sound power level measurements are made.
Modern acoustical measurement equipment at AIRO comprises microphones, acoustical calibrators and sound level frequency analysers – all of the highest accuracy class and regularly verified by calibrations traceable to national reference standards. Signal generation equipment includes dodecahedron loudspeakers, so-called “tapping” machines that drop, at a defined rate and impact velocity, five steel hammers onto a floor surface and a reference sound source for sound power level determinations.
Independent technical oversight through AIRO’s accreditation by UKAS (United Kingdom Accreditation Service) and membership of associations such as the BMTA signals to the customer the value AIRO places on high quality, state of the art test and measurement practice. It also provides opportunities to exchange information and keep up to date with developments in the field. Similarly, staff volunteer work over many years on relevant British Standards Institution committees, sponsored by BMTA and together with participation on the councils and committees of the Association of Noise Consultants and the Institute of Acoustics underpins AIRO’s good standing in the field. This gives AIRO the opportunity to give something back to the mutual benefit of members of the acoustical community.