Acoustic Test FacilitiesNovember 13, 2020 | Anechoic, Testing
Acoustic Test Facilities
Progression of time and technology has meant acoustic test facilities and noise control solutions have become vital to the modern way of life. Recording studios, concert halls and hospital audiology units need to prevent intrusive noises getting in. Car designers, data centres and power plants have to control the noise that gets out. Without acoustic science, we could not live in proximity to many of the things we depend upon; factories, air-conditioning, airports and highways, or effectively use and live with home appliances, workplace tools and mobile devices.
Noise control standards are now tightly defined by government regulations and international standards (for example, ISO 1999:2013 for noise at work, ISO 362 & ISO 16254 for road vehicles or BS8233:2014 Guidance on Sound Insulation and Noise Reduction for Buildings). Without state-of-the-art test facilities, it would be virtually impossible for manufacturers and service providers to achieve high performance standards. IAC Acoustics draws on 70 years of acoustic and materials research to solve these problems by creating high performance acoustic test facilities – making the world as we hear and feel it possible.
IAC Acoustics delivers custom solutions to solve each client’s unique technical, architectural and aesthetic requirements. This turnkey approach is important because ancillary elements such as air conditioning, exhaust ventilation systems, electronic services and temperature control always have to be factored into the core design. An end-to-end project solution is essential in such high performance installations – this ensures the micro design details affecting the performance standards for the testing environment are met.
Anechoic Chambers Designed to ISO 3745:2012
Anechoic chambers offer full range sound suppression means shielding all surfaces from sound penetrations and reflections – walls, ceiling and the floor is covered by acoustic wedges. Since the depth of a wedge determines the range of frequencies it can absorb, you can imagine that it isn’t practical to walk on an anechoic floor. Instead, test equipment and personnel are supported on acoustically transparent mesh walkways.
Everything that breaks through the sound insulation, including light bulbs and ventilation grilles, is purpose-designed and shielded. Personnel are also reflective, so the tests will be often conducted with the room unoccupied . Fully anechoic chambers can achieve incredible levels of performance.
Most facilities are hemi-anechoic, which means they retain a hard floor. This is not only cheaper and more practical but often acoustically desirable. Sound reflections from the ground often provide sound environments akin to real-world conditions and more natural to the ear. Vehicle NVH testing is partly conducted in “vehicle semi-anechoic chambers” (VSACs) which support the rolling wheels on dynamometers.
In reverberation rooms, the floor, wall and ceiling surfaces are designed to reflect rather than absorb sound, creating a random incidence sound field. Reverberation rooms can be designed for testing the absorption properties of a material ISO 354 or can be used for testing the sound power level of a device ISO374. Reverberation rooms for testing the absorption coefficient of a material will have a long reverberation time when empty. Rooms of this type are used to calibrate how test materials absorb sound from different directions or how microphones react to reflected sounds. They are also used to explore vibration-fatigue in aviation components.
Transmission suites are constructed as two reverberation rooms back-to-back. They are used for measuring the transmission loss of a material. Exploring how sound will travel between separated “uncoupled” rooms is often needed in the research and development of new products, particularly for the construction sector, e.g. doors, windows and partition materials.
IAC Acoustics has recently designed, manufactured and installed a transmission suite at Cambridge Acoustics Laboratory Ltd. The new facility provides laboratory sound insulation testing in accordance with the BS EN ISO 10140 series of standards. This adds another reference test facility to IAC’s long standing success in this sector with the likes of BRE, University of Salford, Solent University ISVR, National Physical Laboratory and many specialist research applications.
IAC’s modular, removable acoustic partition system separates the two rooms, in which specimen partitions can be installed for acoustic testing with ease. This creates two highly reverberant acoustic environments, with very low absorption and absolute minimal flanking paths. This focuses sound transfer between the two rooms through the partition element in the centre, enabling accurate testing. The intended use of this facility is to determine the sound reduction index, specifically measuring the Rw value. This is the weighted sound reduction index based on laboratory measurements, a single acoustic figure, as used by contractors and consultants in the acoustic field to specify and compare the acoustic performance of partition elements. The measurements are taken using state of the art rotating microphone booms, omnidirectional speakers and data acquisition systems, to acquire data across 1/3 octave bands ranging from 50Hz – 8KHz.
In application, the test specimen will be installed between the two rooms within the modular partition section. Broad-band noise, minimum 40dB above background level, is generated through the omnidirectional speakers in the source room. The level difference between the source and receive rooms is then used to calculate the effective sound transmission, from one room to the other across each 1/3 octave band. This data is then used to calculate the Rw a standardised value used in industry – known as the Weight Sound Reduction Index.
Testimonial, Cambridge Acoustic laboratory:
“The team from IAC Acoustics are leaders in what they do and this shows in their work. They could not have been more helpful – with their professional and skillful approach reflected in what is an excellent finished product. Our brand new transmission suite at Cambridge Acoustic Laboratory is exactly what we wanted, and we were supported throughout the entire process by a diligent and supportive team from IAC. We recently launched the Lab by opening to the public and have had overwhelmingly positive feedback; our clients are so impressed with the fantastic build quality and sound services we are able to offer as a result of IAC’s input. In addition to the technical expertise IAC were able to provide, we enjoyed working with such a friendly and encouraging team. We could not recommend IAC highly enough and look forward to collaborating on more projects with them in the future.”
Natasha Malcolm-Brown, Sales & Marketing Director, Cambridge Acoustic Laboratory LTD
Professional Acoustic Test Facilities
The design, development and installation of professional grade acoustic test facilities for product development and scientific research is perhaps the ultimate reference in acoustics. Creating a facility which goes beyond ordinary acoustic requirements, enabling organisations to offer acoustic testing and qualification for emerging products and technologies, is a very specialist capability. IAC Acoustics continues to offer market leading test solutions to this extraordinary discipline within acoustics and looks forward to supporting organisations for future needs in acoustic test facilities.