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Test Facilities

Fully Anechoic Chambers

Schedule 60 Microdyne® Chambers 
The IAC Acoustics Microdyne® Schedule 60 anechoic room is designed for the research physicist or engineer who must make precise sound measurements in a free-field acoustic environment. Schedule 60 rooms provide high sound transmission loss (TL) characteristics and have a completely anechoic wedge lined interior to meet these requirements.

For maximum sound isolation, our Schedule 60 rooms are designed as a room within a room featuring certified IAC Noise-lock® and Moduline™ components. The inner room is set on a vibration isolation system created for the specific weight and frequency cut-off of the room.

Schedule 40 chambers are designed for applications and locations where the noise reduction characteristics for a single wall and ceiling construction provide adequate noise isolation.

The single wall construction results in smaller overall outside dimensions and is particularly suited to placement in less noisy areas. In every other respect, the Schedule 40 is similar to the Schedule 60 series with the same standard features and options available.

Microdyne® anechoic rooms come with the following standard features:

  • Anechoic wedges (foam, fibreglass or IAC Metadyne®) with the required low-frequency cut-offs
  • Double or single wall and ceiling construction
  • IAC Acoustics standard ventilation system coupled to the building supply
  • Lighting (interior) minimally acoustically reflective
  • Tubular cable ports
  • Interior non-reflective cable floor system above the floor wedges with a nylon catch net below
  • IAC Acousti-flote™ floor system with vibration isolators
  • One IAC Noise-lock® wedge acoustic door


  • Floor grating for chambers which will house heavy items
  • Additional or larger Noise-lock® acoustic doors
  • Access panels for equipment and test openings
  • Double Acousti-flote™ floor for Schedule 60 anechoic rooms
  • Air mounts, springs or other types of vibration isolators
  • Independent ventilation system
  • RF shielding

Fully anechoic chambers pose a challenge when people need to enter the facility in order to place items under test. IAC Acoustics has developed a range of floor solutions to minimise reflective sound. Typical installations ultilise a grid-based system to maximise the absorption of the floor wedges. We also use a range of cable floors to support people and heavy test objects. For some very high specification facilities, we have even developed a range of retractable floors which completely remove any reflective surfaces when in use to achieve the most accurate measurements.

Cable Floors
IAC Acoustics fully anechoic chambers are typically provided with a tensioned cable floor, situated approximately 100mm above the tips of the floor wedges. Beneath this cable floor is a nylon catch net to prevent debris and small objects falling out of reach.

The cable floor consists of stainless steel cable interwoven in a criss-cross matrix of 50mm separation. Each cable is tensioned from an acoustically lagged steel ring beam by turnbuckles at one end and a coil spring at the other. This ensures that the floor is strong with even deformation and spring characteristics.

Typical uses of high precision anechoic and hemi-anechoic chambers include:

Microphone Calibration

  • Primary calibration, free-field reciprocity method
  • Secondary calibration by the substitution method
  • Frequency response and directivity Sound Level Meter Calibration
  • Pattern evaluation
  • Frequency response
  • Directivity

Psycho-acoustic Testing

  • Sound perception testing is typically used for research and development of products
  • An example of research carried out was by Stable Micro Systems Ltd at NPL in the UK where tests were carried out on the “crispiness” of biscuits and their effects of peoples’ perceptions of taste

Sensory Deprivation Testing

  • Used for military and educational research

Speaker Research & Development

  • Sound power output measurements
  • Physical speaker design
  • Distortion and frequency response

Acoustic Science

  • PhD projects
  • Ultrasound scanning research
  • Virtual acoustics – generating auralisations of concert halls, city streets and other spaces

CE Marking / Certification

  • All machines are required to have a sound power output test carried out prior to being released for sale
  • Testing of toys to ensure suitability for hearing in children
  • Items such as hearing protectors are required to be tested in an anechoic chamber to measure their effectiveness

Hearing Research

  • Free-field audiometry
  • Cochlear implant testing

Pass-by Chambers

Road traffic noise is a main contributor to environmental noise, thus, it is intended to be reduced and limited by legislation in order to increase health and life quality. Vehicle pass-by noise tests are conducted according to the international standard ISO 362, which quantifies the noise emission of a vehicle in an urban traffic environment, by testing on an outdoor track.

Traditional field pass-by measurements are still the only way to certify a vehicle for exterior noise emissions during operation, but an indoor pass-by test provides an extremely powerful and repeatable method of troubleshooting exterior vehicle noise in the controlled environment of a hemi-anechoic chamber.

Instead of making the test vehicle pass two stationary microphones, indoor pass-by measurements place a row of microphones alongside the test vehicle whilst running on a chassis dynamometer and accelerated in the same way as it would be for a traditional pass-by measurement.

IAC Acoustics has designed numerous hemi-anechoic pass-by chambers for automotive manufacturers across the world. Due to the low frequency noise generated by a combustion engine, IAC Acoustics Metadyne® anechoic wedges offer the perfect solution to achieving a suitable testing environment.

New ISO Standards

ISO 362-3 Measurement of noise emitted by accelerating road vehicles

New developments to the ISO Standards are helping to ensure consistency across the latest vehicle tests.

Exterior noise measurement approval to the current ISO 362-1 standard must presently be carried out on certified outdoor test tracks.

Due to environmental influences, these traditional proving grounds do not give the consistency required by the increased demands of the motor industry.

Sound emitted from a vehicle should be tested under controlled conditions independent of weather and other environmental factors.

The forthcoming ISO 362-3 gives the specifications for test facilities to achieve a precision comparable to a certified type approval test track, thereby allowing indoor testing.

ISO 16254 Measurement of minimum noise emitted by road vehicles

With the advances in electromotive vehicles, the minimum sound level emitted is of concern for pedestrian safety.

ISO 16254 is in preparation by the relevant ISO committees to provide a method to measure the minimum noise emission of road vehicles, as well as to quantify the characteristics of any external sound-generation system installed for the purpose of conveying acoustic information about the approach, presence and/or departure of the vehicle to nearby pedestrians.

All IAC pass-by chambers conform to the current drafts of these standards and will allow measurement of noise emitted by an accelerating vehicle and the measurement of the minimum noise emissions.

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