Anechoic Chambers

A Complete Range of Microdyne® Anechoic & Macrodyne® Reverberation Chambers

Since 1949, IAC Acoustics has designed and constructed thousands of acoustic test facilities including several hundred small anechoic and reverberation chambers. These controlled environments encompass a wide range of performance specifications — from simple quality control requirements to elaborate high precision acoustic measurements.

IAC Acoustics’ design engineers and research physicists bring a wealth of experience to provide data for an informed discussion on how to select free-field anechoic chambers and diffuse-field reverberation rooms.

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Anechoic Chamber Definitions & Key Terms

What is an Anechoic Chamber?

An anechoic chamber is precision acoustical measurement instrument, providing a free-field environment or environment without reflections, without noise interference or sound reflection. In an ideal free-field environment, the inverse square law would function perfectly. This means that the sound level from a spherically radiating sound source decreases by 6dB for each doubling of distance from the source. For a free field to exist with perfect inverse square law characteristics, room boundaries must have a sound absorption coefficient of unity at all angles of incidence. In practice this is not quite perfect and deviations from the inverse square law are to be expected. In a rectangular room, all six surfaces of the room are treated with acoustically absorbing materials.

What is an Hemi-Anechoic Chamber?

Hemi-Anechoic Chambers provide a precision free-field environment used to measure sound sources over a reflecting plane. Typical uses include testing microphones, hearing protection devices and hi-fi equipment. The hard, or non-acoustically absorbent floor is typically used when larger, heavier items are to be tested where a fully anechoic facility would be impractical, or when the normal mode of operation is over a reflective plane such as a floor or hard road surface.

Why Choose IAC Acoustics?

IAC Acoustics has successfully carried out a number of turnkey acoustic test facility projects around the world. As a turnkey supplier, everything from the initial concept design through to the final commissioning is carried out by IAC Acoustics. As part of the turnkey process, IAC Acoustics will also be involved in:

Planning applications with local authorities
Noise surveys and acoustic mapping
Architectural design of buildings
Mechanical and electrical installation design
Appointing reputable sub-contractors

By opting for a turnkey solution, costs can be consolidated via one single supplier, reducing overall spend and minimizing administrative input. This is particularly effective if many different acoustic facilities are being installed at one location or if a complete building is required.

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Anechoic Chamber Product Offering

Single Wall STC 40-60 Microdyne® Chambers

Single Wall STC 40-60 Microdyne 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 Single Wall STC 40-60 Microdyne Chamber is similar to the Double Wall STC 70 Microdyne Chamber series with the same standard features and options available.

Double Wall STC 70 Microdyne® Chambers

The IAC Acoustics Double Wall STC 70 Microdyne Chamber is designed for the research physicist or engineer who must make precise sound measurements in a free-field acoustic environment. Double Wall STC 70 Microdyne Chambers provide high sound transmission loss (TL) characteristics and have a completely anechoic wedge lined interior to meet these requirements.

For maximum sound isolation, IAC Acoustics Double Wall STC 70 Microdyne Chambers are designed as a room within a room featuring certified IAC Acoustics 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.

Anechoic Wedges

One practical well proven method to achieve a free-field is to shape sound absorbing material into wedge configurations for mounting on to the interior surfaces. The wedge shaped geometry ensures a gradual change in the acoustic impedance of the transmission media, ensuring that sound waves are absorbed by the material, rather than reflected at an interface.

The effectiveness of the absorption depends on the geometry and materials used. The lowest frequency at which the absorption is effective (cut-off frequency) is inversely proportional to the depth of the wedge. An impedance tube is used for critical adjustment of wedge dimensions before finalizing each design. Due to variations in material characteristics, statistical quality control measures are employed during wedge production to ensure specified acoustic performance.

IAC Metadyne® Wedges

Metadyne anechoic and hemi-anechoic test rooms have been chosen by the world’s leading companies for the many unique advantages they have over rooms built using other materials, such as fiberglass or foam. Metadyne wedges were developed by IAC Acoustics as a solution to some of the problems associated with using 100% foam or fiberglass. IAC Acoustics was the first manufacturer to provide acoustic performance of the highest standard with a range of wedges which are entirely encased in perforated metallic casings.

Metadyne wedges are ideal for large facilities which require low frequencies to be absorbed for testing products such as cars or engines. The rugged wedge construction and their long life span offer advantages to laboratories working with heavy equipment and /or flammable materials.

Metadyne metal-faced anechoic wedges offer:

Guaranteed acoustic performance with very low cut-off frequencies
Compliance with international test standards, including ISO 3745, ISO 3744, ISO 26101
Superior fire and impact resistance
Greater durability and a longer lifespan than any other wedge type
Ease of cleaning to ensure an “as new” appearance throughout their working life
A bright, healthy and safe working environment for test personnel
Many paint options available to match corporate colors

Relevant Test Standards

IAC Acoustics designs and manufactures acoustic testing facilities to meet a large range of requirements.

Some frequently used standards that summarize the acoustic performance requirements of the test facilities are summarized here, along with links to relevant product information.

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Anechoic Chamber Case Studies

Mando America

IAC completed a turn-key project was for Mando America, a company who provides “the most important parts for car chassis and other parts that determine the performance of cars”.

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Cummins Power

The new anechoic chamber included one hemi-anechoic chamber, one reverberation room, one engine test cell, one control room and one preparation area.

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