Eckel - Anechoic Chamber
From Anechoic Chamber
Eckel designs, fabricates and installs anechoic and hemi-anechoic chambers to precise specifications for government laboratories, industrial concerns, and leading universities. Totally integrated systems and designs include requirements such as isolated floors, light and power connections, ventilation, temperature and humidity control, instrumentation sleeves, control supports, working floors, and single and double sound doors.
Anechoic Chambers are echo-free enclosures with a sound energy absorption level of 99% to 100%, or a reflected sound pressure level of 10% or less. The frequency at which the energy absorption drops below 99%, or the pressure reflection exceeds 10%, is known as the low-frequency cut-off. Sound absorption is obtained by lining the walls, ceilings, and floor with wedges or other sound absorbing elements or SuperSoft panels, depending on performance level required and cut-off desired.
Eckel Anechoic Chamber linings represent the most advanced technical thinking in design and construction. Currently we offer fiberglass, foam, and perforated metallic EMW types of sound absorbing wedges, as well as new E-Element concept and SuperSoft panels to accommodate the widest range of testing requirements.
EW Standard Anechoic Wedge
The EW Standard Wedge is the classic design based on the original geometry established by Beranek and Sleeper at Harvard during W.W.II. Current E.W. Wedges incorporate the latest materials and design modifications for a wedge treatment with maximum broadband performance.
EMW Perforated Metal Anechoic Wedge
The Eckoustic Metallic Wedge represents the execution of the classic design with a perforated metal cover versus the original wire hardware cloth. Utilizing high transparency 22 ga. perforated steel or aluminum, the metal cover is virtually acoustically transparent.
E-Element Anechoic Absorbing Wedge
Utilizing a unique geometry the E-Element offers a new dimension in anechoic chamber construction differing from the conventional wedge design. The E-Element is constructed of multiple parallel surfaces with tapered leading edges that alternate 90 degrees out of phase with one another. This creates a sound absorbing array which achieves cut-off with less depth of treatment than conventional 'wedge' designs. [ Patent Pending, Under Development. ]
Acoustic Foam Anechoic Wedge
Acoustic Foams, (polyurethane and melamine) offer acceptable acoustical characteristics in many applications and may be more economical than traditional treatments. Polyurethane foam chambers must incorporate a sprinkler system because they are hazardous if combusted. Properly designed foam chambers work well in many applications.
SuperSoft Panel Lining / Wedge
SuperSoft panel lining for acoustic test facilities was developed to fill 'a niche' when a full anechoic chamber was not needed. An existing or new structure could be lined with an extremely high performance acoustic panel to yield a test environment satisfactory for general product testing and noise emission,
A Production sample from every 100 units is tested to verify design, materials, and cut-off frequency. The test is conducted in accordance with the Impedance Tube Method- ASTM-C 384-90a. Wedges or sound absorbing elements shall have a low frequency cut-off in Hertz (Hz). Above this frequency, they shall have a coefficient of absorption value of 0.99, or a ratio of reflected sound pressure to incident sound pressure of 10% or less.
After the full installation of the Chamber is complete, a test shall be conducted to guarantee chamber performance. The test is conducted in accordance with ISO 3745: Inverse Square Law, ANSI 12.35 1990 (R1996). Wedges or sound absorbing elements shall have a low frequency cut-off in Hertz (Hz). Above this frequency, they shall have a coefficient of absorption value of 0.99, or a ratio of reflected sound pressure to incident sound pressure of 10% or less.
Attenuating Structures In order to obtain a suitable sound environment, the anechoic chamber lining is installed in a proper noise isolating structure. This enclosure may be one of several types of construction built on an isolated floor, or floated on springs or other vibration isolation material.
A masonry enclosure is typically used in new construction, or when the anechoic facility is planned as an integral part of a new building. A 200mm or 300mm (8' or 12') masonry block usually provides adequate noise reduction. The addition of an inner panel room will provide increased noise reduction when required. Walls should be constructed on an isolated reinforced floor separated from the building floor or in a pit to allow the working floor in a chamber to be flush with the host room floor.
Eckel provides enclosures built from Eckoustic panels with solid faces on both sides. Eckoustic panel rooms are completely pre-fabricated in the factory and can be quickly erected in an existing facility. These modular enclosures allow for flexible arrangements of doors and utilities. Doors are structurally and acoustically compatible with the wall construction. Hard spots or internal framing are provided for attachment of hardware. Penetrations for lights, power, instrumentation wiring, and ventilation are incorporated into the panel construction.
Working Floors (Cable or Grating)
Since Anechoic Chamber Wedges are not designed to support heavy loads, a working floor must be provided over the top of the floor wedge points. Eckel recommends two types for general use: spring tension cable floors and grating floors (expanded and subway grating). Spring tensioned cable floors are best from an acoustical standpoint, whereas floor gratings are desirable where concentrated loads must be supported. Floor gratings are provided in sections so they can be removed during testing.
The Anechoic Chamber entrance sound attenuating doors can be fabricated in a variety of designs, including swing-in or swing-out hinged type, sliding-wall type, or track-riding type. Also offered is the space-saving interlocking wedge door. Here, Anechoic wedges are mounted directly onto the door. When the door is swung open into the chamber, the wedge points interlock with those on the adjacent wall, minimizing the amount of lost space in the chamber
The ventilation system in the Eckel anechoic chamber is designed to maintain a uniform temperature, provide fresh air for humans and/or animals and facilitate proper combustion in air-consuming equipment. Ten to twelve air changes per hour of the free field volume will generally maintain uniform temperature and provide ample fresh air for humans or animals, while removing normal heat from lights, body radiation, and instrumentation.
Eckel anechoic linings are constructed according to a strictly supervised installation protocol. chamber linings are installed on roll formed wedge tracks attached to wall and ceiling surfaces by means of a 'Z' bar mounting system. As wedges are erected, the space between the wedges is filled with light density compressible fiberglass or melamine foam.
Eckel installs all hangers and brackets required to support instrumentation and test specimens. This includes a network of all necessary cables or wires. Eckel provides engineering or design data pertinent to the support of any type of equipment within an anechoic chamber upon request to the purchasers, and their consultants or engineers.
Electrical power, wiring, and other services are introduced into the anechoic chamber by pipe sleeves that pass through the basic structure and wedges. Eckel Industries plans pipe penetrations carefully so that they enter the chamber through the valleys of the wedges and not the joints between the wedges.
Electric services are always installed in compliance with local or UL-approved regulations. Electric light, conduits, and outlets usually penetrate the structure through the wedge valleys and terminate at that point with the appropriate outlet or fixture.
Anechoic Chambers shall be isolated from structural vibration by one of the following systems.
reverberation roomsEckel Reverberation rooms are designed for the determination of sound output of noise sources, transmission loss of partitions, insertion loss of silencers, response characteristics of microphones, and random incidence absorption coefficients of materials. Eckel reverberation rooms satisfy reverberant test requirements and meet specific interior sound levels and other environmental requirements necessary for proper test measurements.
Other Available Features
Eckel offers RF shielding, temperature and humidity control and other special features depending on client needs. Fiberglass cloth cover option protects against fiber migration, especially where the chamber will be incorporated into a wind tunnel test configuration.