No Such Thing as Too Quiet

Sometimes proper selection and placement of insulating materials is part art, part science. Imagine a dishwasher so quiet you have to open the door to see if it’s on. Or how about an automobile as quiet as a Rolex, a laser printer whose flashing LED is the only indication it’s printing, or a vacuum cleaner that needs an indicator light to signal it’s operating. Consumers are demanding this level of noise reduction, and OEMs are scrambling to provide it. Quiet operation effectively gives products a higher perceived value. But sound insulation can also add weight and assembly cost. A deeper understanding of noise reduction principles can keep the cost-benefit analysis in the black. Noise reduction is more than just a creature comfort; it has practical applications. Reduction of structure-borne noise in computer disk drives, for example, speeds access and boosts storage capacity. In the workplace, quiet improves productivity, minimizes distractions, protects hearing, and permits better communication. In some products, such as luxury automobiles, the goal is more sophisticated than simply reducing noise. Instead, acousticians apply the field of psychoacoustics to deliver a particular sound. They combine sounds from several areas of the vehicle to deliver a distinctive audio signature associated with a particular vehicle brand. A filtering out of all noise frequencies may be counterproductive. Often it results in a sharp