Controlling noise, vibration and harshness (NVH) is a critical part of quality assurance in consumer goods manufacturing. From cars and light trucks to washing machines, air-conditioners and pumps, finding the right soundproofing solutions can improve end-user perceptions of product quality and yield a major marketing advantage.
Everyone wants devices that run smoothly and quietly, but cost is always paramount for mass-produced consumer goods. So, how can engineers hit NVH targets and control cost at the same time?
Acoustic Damping
One strategy is to attack noise, vibration and harshness at the source. This requires balancing rotating assemblies and eliminating lost motion from linkages, as well as substituting vibration-inducing components with smoother running options, such as using double Cardan or CV joints in place of conventional universal joints.
Precise and accurate alignment of drive components also reduces NVH, as does shock mounting of vibration-prone components using elastomeric components or hydraulic dampers. For most mass-produced products, however, these solutions are complex, expensive and deliver a poor cost/performance ratio in production.
There’s also another major factor: resonance.
Most mechanisms are housed in a sheet metal or resin enclosure, and as vibrations feed through the unit housing, first-, second- and even third-order resonances can stack to create objectionable levels of NVH, which then radiates through panels and housings much like the subwoofer in a high-end audio system.
Some of the more elaborate soundproofing solutions here include designed-in stiffening ribs and contours, sandwich construction and even tuned mass dampers or active electronic noise suppression. All are expensive to design, engineer and manufacture.
Acoustic Tape
Passive soundproofing solutions are the most cost effective. Applique sound deadening pads made from acoustic damping material are a low-cost solution, as are structural adhesives that decouple and absorb the resonant frequencies. Isolating vibrating panels with elastomeric bumpers or pads is another strategy that sees widespread use, particularly in vehicle soundproofing.
3M provides multiple acoustic management solutions in the form of acoustic tape, offering this kind of low-cost approach to acoustic damping.
3M’s Vibration Damping Tape uses a constrained layer damping technique that combines an adhesive with an elastomeric damper constrained by aluminum foil. Passing frequencies that excite the elastomer are prevented from transmitting or radiating the energy by the foil layer, instead converting the acoustic energy to heat.
The result adds acoustic dampening functionality while also providing a cost-effective soundproofing solution that can replace expensive mechanical fasteners in many applications.
Where rigid panels are bonded to a frame or other panels, the panels themselves can serve the constraining function. Acoustic tapes such as 3M VHB tape use a viscoelastic core and the panels’ own rigidity to damp vibration and deaden sound. These proven bonding products are widely used in manufacturing as a low-cost replacement to fasteners.
If the noise source is caused by surface contact that, for functional reasons, cannot be constrained, the best approach is to reduce friction between the moving components. 3M Slick Surface Tapes use polyethylene (UHMWPE) and Teflon (PTFE) formulations to block the transfer of noise, vibration and harshness between contact surfaces.
For simple conditions, such as housing “feet” or access panel stops, 3M Bumpon pads can be easily applied using their self-adhesive backing.
For situations where design or manufacturing constraints force the use of sound-deadening layered solutions, like vehicle soundproofing, 3M Thinsulate Acoustic Insulation is designed to absorb sound.
Acoustic Tape Benefits
3M also offers a wide range of laminating adhesives, which are useful when bonding proprietary composite sound deadening panels, a major issue in vehicle soundproofing as advanced materials replace metals.
By designing automotive, aerospace and mass-produced consumer goods with acoustic tapes, adhesives and appliques in mind, engineers can reduce cost and complexity. For example, they will be able to use simpler power and drive systems, relaxed manufacturing assembly tolerances and lower cost components, while still delivering an end-user experience that minimizes noise, vibration and harshness.
In addition, designing with an eye toward adhesive soundproofing solutions makes faster and lower cost assembly possible by replacing screws, bolts, rivets and clips in many applications.
Applied acoustic damping materials such as 3M's Thinsulate tape offer another benefit: the ability to design large, flat panels without the risk of the “oil canning” effect common to these passive radiators. The ability to control noise and do away with complex surface stiffening features also reduces mold cost in injection molded parts, and allows easier fabrication of sheet metal components with fewer forming stages and faster, lower-cost finishing.
Controlling Noise, Vibration and Harshness
Design for assembly often conflicts with design for performance, but in terms of acoustic management, it’s possible to have both with the right adhesive products. 3M offers design assistance to engineers through the 3M IATD TSR Program and the 3M IATD Design Solutions Program, and can conduct design reviews to identify the best design solutions.
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3M has sponsored this post. All opinions are mine. –James Anderton