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acoustic property of “constrained layer damp- Imitations using parallel fusion of small diameter ing.” All materials have a “natural harmonic” or a tubes can not match the performance of Nida- frequency at which they will sympathetically Core, utilize inferior grade plastic compounding vibrate. Polypropylene’s “natural harmonic” is at that is brittle in cold temperatures and fail unpre- a very low frequency of 125 to 150 Hz. The nor- dictably as compared to perfect hexagonal mal “problem hearing range” is 1000 to 3000 Hz. shaped cell cores like Nida-Core Corp ‘s Struc- Therefore, the material’s natural harmonic is far tural Honeycomb(H8PP and 8HP). below the “problem hearing range.” The nature HONEYCOMB SUMMARY of sound is that the lower the frequency, the In short, many claims and counter-claims may be greater amount of energy is required for the made about which product has the best proper- sound to be heard. To quantify the difference, ties for a given application. The structural proper- the amount of energy required for a 50-Hz noise ties that you actually achieve are very dependent to be noticed is 1 million times that required for on the manufacturing process. You must design a 3000-Hz noise. This constrained layer damping structures with physical properties based on real serves to limit the conduction of structure-borne values that the shop can consistently produce. sound in applications such as bulkheads, decks With elongation exceeding that of any other and stringer systems in boats, automobile load type of core material, Nida-Core Structural Honey- floors, sound enclosures and speaker industrial cabinets, comb is the toughest, most resilient core avail- etc. To prevent conduction of sound from one able. Under stresses beyond its design loads it de- side to the other in most single-wall applications, forms and stretches; however, it remains intact either the wall has to have a lot of mass or sub- and, unlike with industrial foams, stress cracks do not travel, stantial absorbers need to be added on the sur- but remain localized for easy repair. Polypropylene face. (Sound transmission straight through a wall honeycombs remain a viable core of choice for is referred to as “airborne” sound, even when a superstructures, floors, bulkheads, stringers and wall separates, for example, two rooms other- hull sides as well as numerous small composite wise completely sealed off from one another.) parts and structures. It is difficult to compare core Bulkheads designed with H8PP successfully re- materials using only he mechanical data. As duce the sound transmission through damping, noted previously, many other properties must be where other, heavier construction materials may considered to properly evaluate the overall situa- resonate sympathetically and pass the sound on tion. While some core materials have certain prop- to the other side. By thermo-fusing polyester erties that are exemplary, one shouldn’t look at based scrim cloth with polypropylene-based these isolated properties without taking into ac- barrier film under-layment, Nida-Core provides a count other aspects, including cost. While most 100 percent bonding surface compatible with cores provide one or two desirable properties, most resin systems. The dead air space inside only Nida-Core RIGID-ELASTIC TECHNOLOGY is the cells provides insulation (an R factor of 3.3 designed to provide them all — insulation, stiff- per inch of thickness) not unlike the double-pane ness, chemical resistance, toughness and light windows in a modern dwelling. While most cores weight and sound absorption Fully considered, excel in providing one or two desirable proper- nothing available provides the cost/performance ties, only Nida-Core RIGID-ELASTIC TECHNOL- benefits of RIGID-ELASTIC TECHNOLOGY from OGY is designed to provide all of them — insu- Nida-Core. lation, stiffness, chemical resistance, tough- ness and light weight —with the added bonus of sound absorption. NOT ALL PLASTIC HONEYCOMBS ARE EQUAL ! Only Nida-Core Structural Honeycombs have the proper hexagonal cell structure. Only Nida-Core Structural Honeycombs use a proprietary copoly- mer composition to achieve a superior tem- perature tolerance/elasticity combination. Only Nida-Core is extruded in large blocks fused to- gether without using low-melt polymers.

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