Variable Density Materials Deliver Unmatched Isolation Performance
The technology behind Herzan’s acoustic enclosures was originally developed by Herz in Japan about twenty years ago. The AEK was made to provide an exceptionally quiet environment for sensitive research instruments. After studying Herz’s technology and production techniques, Ann Scanlan founded Herzan and brought the AEK concept to America. Herzan continues to develop and refine the AEK design. Over the past fifteen years, Herzan has worked with instrument makers, namely atomic force microscope (AFM) companies, to develop a very high performance enclosure that also offers excellent usability. In addition to standard enclosures, Herzan also offers an array of features and customized enclosures that are built to customers’ specifications.
Variable Density Material
There are basically two ways to isolate an instrument from acoustic noise: Noise reduction or noise absorption. Noise reduction is the blocking or deflection of sound energy. The best way to achieve noise reduction is to use material that is rigid, massive, and high density. Materials that are soft or low density transmit noise easily and are not well-suited for deflecting noise.
Absorption of noise requires different characteristics. Softer materials can actually be quite effective at absorbing sound. Pliable materials with high surface area, such as foam sheets, are great for absorbing, and thus neutralizing high frequency noise.
Depending on the frequency and energy level, some noise is more susceptible to deflection, and some is more susceptible to absorption. Since an ideal isolator will provide noise reduction over a broad frequency spectrum, one should employ materials of variable densities to achieve maximum noise reduction. Herzan enclosures employ eleven layers of sound damping material with a proprietary combination of properties to ensure maximum performance at all frequency levels.
Adding mass is another great way to isolate an instrument from noise. Adding mass increases the impedance of a system, so it will require more energy to excite the system. This makes adding mass to an object an effective means of eliminating low frequency noise, which tends to be lower energy.
Extremely massive systems present their own challenges in terms of mobility and usability. Herzan acoustic enclosures are designed to be massive, but a number of technologies are employed to mitigate the effects of using a massive enclosure. Precisely tuned gas springs allow the door to be opened with minimal force. Heavy-duty handles and attachment points are provided to make lifting the hood more manageable. Casters are included so the systems can be rolled into place with minimal effort.
A system that is not well-supported or adequately rigid will have poor stability. Lack of stability will translate into structural resonances which amplify incoming kinetic energy. This is an important consideration for acoustic isolation because acoustic energy, when it encounters a solid structure, imparts its energy in the form of mechanical vibrations. Even if a soundproof hood has good acoustic properties, if it is not structurally stable then it will transmit acoustic energy into the system in the form of mechanical vibration.
Herzan acoustic enclosures are built out of steel, not wood, plastic, nor other flimsy materials. The support frame also contributes to the system’s stability. The support frame is constructed out of welded steel tubing which is highly rigid. The frame has cross-braces, ensuring good support for the hood itself. The support frame is also offered with the NanoDamp option, which increases its resistance to the effects of mechanical noise.
Parallel surfaces are not optimal when creating a soundproof hood. Parallel surfaces allow sound waves to propagate quite efficiently. Sound waves can even form a standing wave when bouncing off of parallel surfaces, effectively turning the inside of a box into an isolator. This is why anechoic chambers, such as those used in recording studios, are lined by egg crate foam or angled tiles.
Because of this phenomenon, a cube shape is less than optimal for acoustic enclosures. Herzan employs curved doors and octagonal shapes for their hoods to avoid easy propagation of sound waves internally. The shapes of the enclosure are also carefully chosen to provide great ergonomics and a wide angle of access to the instrument contained within.
Airtight vs. Usable
None of the above measures will be effective if there is a poor seal on the enclosure. As acoustic energy travels through the air, any air gap presents the possibility of transmitting noise into the enclosure. Ideally, an enclosure would be completely sealed so that it would be airtight. Of course, this would render the enclosure impossible to use. Instruments require access for sample changing and service. Modern instruments also require cables to be fed into the enclosure, for power, control, and data transfer. Many instruments also require a window for viewing the instrument while in use.
Much of the noise isolation technology in Herzan enclosures is directed towards providing a high level of usability without degrading acoustic isolation performance. Some examples of this technology include the proprietary design of the windows, which provides a good view of the instrument without allowing troublesome noise to enter the enclosure. Great care is taken in the specification and application of gasketing to ensure a good seal around the door and other access points. The cable clamp is specially designed to allow cables to enter the enclosure without creating air gaps.
Advantages of Herzan Acoustic Isolation
- Excellent attenuation
- Isolates high and low frequency noise
- Great ease of use without compromising performance
- Damped cable clamps eliminate parasitic noise
- Unique window design provides easy instrument viewing
- Rigid frame provides added stiffness
- Doors open and close with minimal force
To request more information or a quotation for this or other Herzan products, contact IL Photonics.