Custom NVH, Shock & Vibration Control Materials: Isolation, Damping & Cushioning Pads

They solve the problem in opposite ways. Isolation uses a soft, resilient, low-loss element (a spring) to lower a system's natural frequency so the disturbance frequency falls in the isolation region, where transmitted force is less than the input; it works by mismatching frequencies, not by absorbing energy. Damping uses a lossy, high-hysteresis material to convert resonant vibration energy into heat, which lowers the peak at resonance; it works precisely by absorbing energy.

A good isolator and a good damper are nearly opposite materials, so the first thing to get right is which job you actually have. Many real mounts use a little of both: a resilient isolator with enough damping to tame the resonance peak it passes through on start-up and shut-down.

It falls straight out of the transmissibility equation for a single-degree-of-freedom system. When the frequency ratio f/f_n is below 1, the mount transmits roughly the full input or amplifies it; at f/f_n=1 it resonates and transmissibility peaks; and the curve crosses transmissibility=1 exactly at f/f_n=√2 for every damping value. Only above √2 does transmissibility drop below 1, which is the isolation region.

The practical consequence is that a mount must be soft enough (and the supported mass heavy enough) to put the natural frequency well below the disturbance frequency, so the running speed lands comfortably above the √2 crossover. A mount that is too stiff lands the disturbance near or below resonance and makes the vibration worse. The isolation region finder on this page shows the relationship.

Start with load and environment. For a heavy machine in a controlled indoor environment, natural rubber gives excellent resilience and high load capacity. If the mount lives outdoors or near oil and ozone, neoprene (or rebonded neoprene for heavy structural pads) is the durable choice because it resists weather, ozone and oil where natural rubber would swell and crack.

For light loads where you need a controlled, soft curve at low stress, electronics, instruments and precision equipment, microcellular polyurethane (PORON or HyPUR-cel) holds its shape better at low pressure than a coarse rubber pad.

Confirm the load rating, temperature range and chemical resistance of the specific grade against the manufacturer's data sheet, and send the static load per pad and the footprint so the bearing stress can be checked.

The loss factor (η, eta) is a dimensionless measure of how much vibration energy a material dissipates per cycle relative to the energy stored; a higher loss factor means more damping. It is measured per ASTM E756 by the damped cantilever-beam method: a strip of the damping material is applied to a test beam, the beam's resonances are excited, and the loss factor and modulus are extracted from the response over roughly 50 to 5000 Hz.

Loss factor is both temperature- and frequency-dependent, so a damping material has a band where it works best; the data sheet gives the curve. When you specify a damping treatment, match the material's peak-loss temperature and frequency to your panel's resonance, and remember that the effective loss factor of a treated structure also depends on the construction (free-layer versus constrained-layer), not the material alone.

Vibration is a continuous, often periodic oscillation described by frequency and amplitude; shock is a short, high-amplitude transient described by peak acceleration and pulse duration. They do change the material emphasis. For steady vibration, isolation and damping dominate, and you size a resilient mount to put the natural frequency below the disturbance.

For shock, the job is to absorb a burst of energy and limit the peak force passed through, then recover; microcellular polyurethanes (PORON, HyPUR-cel) and vinyl nitrile lead because their cell structure absorbs energy progressively and bottoms gracefully rather than spiking.

A part that must survive both a defined vibration profile and a shock pulse is qualified against the relevant MIL-STD-810 methods, and the pad is chosen so it neither over-compresses under the steady load nor bottoms hard on the transient. Send both the steady duty and the shock pulse so the material and thickness can be matched.

BSR is the noise an assembly makes against itself, and it has three flavors with three fixes. Squeak is stick-slip friction between two surfaces that grip and release as they move; the fix is a low, stable friction interface, classically SAE pressed felt, sometimes a soft foam or a low-friction tape, placed along the contact line. Rattle is a loose part knocking against its surroundings; the fix is a soft foam or elastomer cushion (vinyl nitrile, soft PORON) that takes up the gap and absorbs the impact.

Buzz is a thin panel resonating; the fix is a damping layer that drains the resonance, or a stiffener that moves it. The common thread is that the parts are thin, precisely placed, and to the contact geometry. H-O converts felt, foam tapes and soft elastomer parts to length and profile with adhesive and liners for line installation.

Reach for silicone when temperature or a flame rating governs. BISCO silicone foams hold their mechanical properties across a wider temperature span than polyurethane or natural rubber, both hot and cold, and specific grades reach UL 94 flame ratings up to V-0. That makes silicone the move for isolation, cushioning or acoustic lining near heat sources, in flame-rated enclosures, or in battery cell-to-module joints that run hot.

The acoustic A2 grades are used for cavity lining. The trade-off is that for ordinary ambient-temperature isolation, silicone is usually not the most cost-effective or highest-load choice, polyurethane and rubber lead there, so use silicone where its temperature and flame advantages are actually needed. Confirm the exact temperature range and the UL 94 rating for the specific grade and thickness on the data sheet.

Because an isolator that takes a permanent set drifts off its design point. Compression set is the permanent thickness a material loses after being compressed, held and released, measured per ASTM D395 (and per the cellular-rubber procedures in ASTM D1056). When a mount sets, it thins out under the sustained weight of the equipment, which raises its stiffness, raises the mounted natural frequency, and can push the disturbance frequency back toward the resonance peak, degrading the isolation you designed in.

A set damping layer can also lose contact and stop working. This is why microcellular polyurethane and quality elastomers are specified for low compression set in sustained-load mounts, and why cork-rubber is chosen where very low creep is needed in a thin shim. Call out the service life and duty cycle so the set behavior can be checked against the grade data sheet.

Up to a point, and then no. A softer or thicker pad lowers the mounted natural frequency, which moves the disturbance further into the isolation region and improves isolation, that part is true. But three limits bite. First, a pad that is too soft for the load over-compresses, stiffens as it bottoms, and loses the low natural frequency you wanted.

Second, a very soft mount allows large static deflection and rocking, which can be a stability or alignment problem for the equipment. Third, more static deflection means the system passes through a lower resonance on start-up and shut-down, so you may need damping to control that peak.

The right answer is to size the pad so the working stress sits where the material holds a controlled curve, put the natural frequency safely below the disturbance, and add damping if the start-up resonance matters, not simply to specify the softest, thickest foam available.

Those standards apply to a measurement or an assembly, not to a raw material on its own. ISO 10846 is a laboratory method for measuring the vibro-acoustic transfer properties (dynamic transfer stiffness, transmissibility) of a resilient element under a stated preload; a mount can be characterized by an ISO 10846 measurement, but "certified to ISO 10846" is not how the standard works.

MIL-STD-810 is a set of environmental test methods, including shock and vibration, that an item of equipment is tested against; a pad supports the equipment's compliance, but the rated result belongs to the tested assembly. So the honest framing is that H-O materials are evaluated against and support compliance with these methods through the manufacturer's data sheet; H-O does not independently certify a material to them unless that is explicitly stated on the quote.

If you need a measured dynamic-stiffness or transmissibility number, that comes from a lab test of the specific part under your preload.

Five things move a recommendation from a guess to a real direction: the goal (isolation, damping, shock, or BSR), the static load per pad and the bearing footprint, the disturbance frequency or running speed (and any target natural frequency), the operating temperature, and the environment (indoor, outdoor, oil, chemical).

Add the part geometry or a drawing, the adhesive and liner needs, and the prototype and annual volume, and engineering can match a family, a grade direction and a converting approach, then confirm the grade-level values against the manufacturer's data sheet.

The "What to send H-O" box below lists these. If you only know the symptom, "this panel buzzes," "this cabinet walks across the floor," that is a fine starting point too; describe it and we will work back to the numbers.

H-O is a precision converter, not a raw-material producer. We do not extrude or mold the foam and rubber; we buy sheet, slab and roll stock from the material manufacturers and convert it to your drawing, by die-cutting, kiss-cutting, laser and waterjet cutting, adhesive lamination, slitting and kitting, with material traceability and lot-level data-sheet records.

Every NVH, shock and vibration part is made-to-order; we do not carry finished parts in stock and we do not advertise a no-minimum policy, though prototype quantities through full production runs are equally welcome and the minimum varies by material and part.

Prototype and production timing is summarized in the process strip near the top of the page and on the quote form. Send your drawing or describe the equipment and the disturbance through the form below for a specific quote.