Acoustic Enclosures for Scientific Instruments – Principles and Benefits

The technology behind the Herzan's AEK series of acoustic enclosures was originally developed by Herz in Japan around 20 years ago. The AEK series was created to offer a quiet environment for sensitive research instruments. Ann Scanlan studied Herz’s technology and production techniques and brought the AEK concept to the US. Herzan continues to develop and refine the AEK design.

Herzan has worked with instrument manufacturers, primarily AFM companies, over the past 15 years to develop a very high performance enclosure that also offers excellent usability. Along with standard enclosures, Herzan also offers an array of features and customized enclosures that are built to customers’ specifications.

Previous Design of AEK Enclosure

Figure 1. Previous Design of AEK Enclosure

Variable Density Material

There are two ways of isolating an instrument from acoustic noise - by noise absorption, or noise reduction. Noise reduction is the blocking or deflection of sound energy, which can be achieved by using material that has a high density, and a high rigidity. Materials that have a low density or are soft transmit noise easily, and are not well-suited for deflecting noise.

Noise absorption requires different characteristics. Softer materials can effectively absorb sound. Pliable materials with high surface area, such as foam sheets, are great for absorbing, and hence neutralizing high frequency noise.

NanoDamp Frame Response Curve

Figure 2. NanoDamp Frame Response Curve

Some types of noise are more susceptible to deflection and some to absorption. As an ideal isolator will provide noise reduction over a broad frequency spectrum, materials of variable densities should be employed to achieve maximum noise reduction.

Eleven layers of sound damping material are employed by Herzan enclosures, with a proprietary combination of properties to ensure maximum performance at all frequency levels.

Another way to isolate an instrument from noise is to add mass. The impedance of a system increases by adding mass, which means that more energy is needed to excite the system. Therefore, adding mass helps in eliminating low frequency noise, which is low energy.

Herzan acoustic enclosures are massive, however they have a number of technologies to mitigate the effects of using a massive enclosure. The door can be opened with minimal force thanks to precisely tuned gas springs. Lifting the hood is made more manageable using heavy-duty handles and attachment points.

Structural Stability

A system without adequate support or rigidity will have poor stability. Structural resonances will be caused due to lack of stability. If a soundproof hood has good acoustic properties, but is not structurally stable, it will transmit acoustic energy into the system in the form of mechanical vibration.

Herzan acoustic enclosures are made of steel, and the support frame is made of highly rigid welded steel tubing. The frame has cross-braces, ensuring good support for the hood itself. The NanoDamp option is also offered with the support frame, increasing its resistance to the effects of mechanical noise.

Form Factor

While creating a soundproof hood, parallel surfaces should be avoided, as they allow sound waves to freely propagate, or even generate standing waves. for this reason, anechoic chambers such as those in recording studios are lined by angled tiles or egg crate foam.

Parallel surfaces

Figure 3. Parallel surfaces

Herzan uses curved doors and octagonal shapes for their hoods, to ensure that sound waves are not easily propagated internally. The enclosure shapes are also selected carefully to offer great ergonomics and a wide angle of access to the instrument contained within.

Airtight vs. Usable

If there is a poor seal on the enclosure, none of the above measures will be effective. Any air gap will cause noise transmission into the enclosure. Obviously it is not possible to completely seal an enclosure, since instruments need to be accessible for sample changing and service. Modern instruments also require cables to be fed into the enclosure, for power, control, and data transfer. There is also a need for a window for viewing the instruments while in use.

Standard cable clamp

Figure 4. Standard cable clamp

The noise isolation technology used in Herzan enclosures is targeted at offering high level of usability, as well as efficient acoustic isolation performance. The design of the windows offers 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 exclusively designed to allow cables to enter the enclosure without creating air gaps.

Benefits of Herzan Enclosures

The benefits of Herzan enclosures are:

  • 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

About Herzan LLC

Herzan provides high performance environmental solutions for precision research instruments. They include acoustic enclosures, vibration isolation systems, Faraday cages, and site survey tools. Herzan specializes in supporting nanotechnology research, but also offers solutions for product testing, in-vitro fertilization, and many other applications.

Herzan understands that every application and environment is different, so it collaborates with customers to create comprehensive integrated solutions that satisfy their unique demands.

Herzan was founded in 1992 by Ann Scanlan in Orange County, California. Originally, Herzan was established as an American subsidiary of Herz Company Ltd., a Japanese company specializing in vibration control. The name Herzan comes from the amalgamation of 'Herz' and 'Ann'.

This information has been sourced, reviewed and adapted from materials provided by Herzan LLC.

For more information on this source, please visit Herzan LLC.

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