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Silent Running PUBLIC ACCESS

There are Rewards for Being Quiet.

[+] Author Notes

Executive Editor.

Mechanical Engineering 126(02), 42-43 (Feb 01, 2004) (2 pages) doi:10.1115/1.2004-FEB-5

Abstract

Several companies are offering home appliances and commanding soaring prices for them, largely because they promise to be quiet. Bosch Home Appliances makes a series of dishwashers designated SH, which it markets as the quietest in North America. Motors and pumps are designed to keep noise down, and there is triple sound insulation on the higher-priced models of the line. Electrolux North America has introduced a vacuum cleaner called Harmony, which it promises will run far quieter than the common variety. One of the key sound damping features is a layer of foam that surrounds the motor. Electrolux adds that the foam also adds a sealing layer so cleaning suction is n’t lost through vacuum leaks. Thus, in addition to suppressing noise, the foam improves the efficiency of the appliance. The Duet washers have a variety of sound quelling features. The Duet is driven by a quiet-running three-phase brushless motor. The machine has a high-performance drain pump that never has to strain to work at its limit. In order to make a Duet, the washer has a comp anion dryer that looks almost identical. The dryer, which is made in Marion, Ohio, is also designed for quiet operation and retails for more than $800.

Article

We may have found what's golden about silence. People are willing to pay a handsome premium for it.

Noise, after all, can be damaging both to the state of mind and to the sense of hearing. And, as Dan Snyder and Elizabeth Smith of SKF USA Inc. pointed out last December, in their Feature Focus article, "The Noise That Annoys," "quiet products equate to quality products." Quiet operation confirms that nothing is bent, broken, rubbing, or shaking loose.

What's more, if that quiet operation is taking place in your home, you don't have to listen to it when the TV is on.

That's why a number of companies are offering home appliances and commanding high prices for them, largely because they promise to be quiet."

Bosch Home Appliances is one of them. The company, a subsidiary of the German appliance maker Bosch und Siemens Hausgeräte GmbH, makes a series of dishwashers designated SH, which it markets as the quietest in North America. Motors and pumps are designed to keep noise down, and there is triple sound insulation on the higher-priced models of the line.

And in this series of appliances, the higher-priced models are just that. In most stores, a customer can pay less than $200 for a reliable dishwasher. Bosch says that its super-quiet models sell, on average, for $499 to $1,499.

The company says the noise barriers are a coated metal layer, a cotton fiber layer, and a heavy-duty bituminous layer. (Buyers of the two lower-priced models in the series have to settle for just two layers of sound isolation.)

Bosch suspends the electric motor on rubber hammocks to keep it from communicating acoustic vibration to the frame. The company says it also reduces noise by using separate pumps for washing and draining. Each one can be smaller, and therefore quieter, than a single pump with a double function.

The dishwasher has no front vent for steam to escape into the room, so another source of noise is prevented. The company also points out that this design feature makes for extra safety in homes with small children.

Another item that contributes to the quiet of all Bosch's SH dishwashers is a solid molded base, which contains sound.

Besides being quiet, the dishwashers are smart. They contain turbidity sensors that monitor the amount of soil in the water and can direct the washer to skip a water fill when appropriate. The highest-priced models add a second sensor, which checks the cleanliness of the water and can delete fresh water fills or change the temperature as needed. The machines will also automatically shut down if water is detected in the base.

They still have to be loaded by hand.

Electrolux North America says its market research has identified the vacuum cleaner as being high on the list of annoying noisemakers in the home. So last fall it introduced a vacuum cleaner called Harmony, which it promises will run far quieter than the common variety. One press notice said it was "four times quieter."

However, the motor of the new model is rated at 1,100 watts, or about 1.5 horsepower, more than you need to chase away the cat. The manufacturer says it was able to put a lid on the noise so it won't even wake the baby.

One of the key sound-damping features is a layer of foam that surrounds the motor. Electrolux adds that the foam also adds a sealing layer so cleaning suction isn't lost through vacuum leaks. Thus, in addition to suppressing noise, the foam improves the efficiency of the appliance.

The company says it has designed the curve of the hose to control airflow and reduce turbulence, which is another source of noise. According to Electrolux, "Within the bend of the hose, 86 strategically placed holes serve as an acoustic mesh screen to filter airflow over a greater area, thus reducing sound emission."

Electrolux says that the floor nozzle is aerodynamically designed to let air flow freely and to avoid turbulence.

The Harmony's retail price hovers around $400. It's certainly not the highest-priced vacuum cleaner available. If you work at it, you can spend $1,000 or more to get one. But the Harmony costs perhaps three times as much as you'd expect to pay for the standard workhorse.

Meanwhile, Whirlpool Corp. has had several new ideas for cleaning clothes over the past few years—including a kinder and gentler agitator, and a washing machine that bounces clothes instead of beating them.

Now, its top-end washer brand is Duet, which the company calls its quietest.

The Duet washers have a variety of sound quelling features, according to Markus Thielemann, an engineer with Whirlpool in Germany, where the washer was designed and is manufactured. Machine controls are electronic, and therefore silent, instead of mechanical. Inlet valves were optimized to reduce noise from the flow of water.

The Duet is driven by a quiet-running three-phase brushless motor. The machine has a high-performance drain pump that never has to strain to work at its limit.

The underworked pump is held in place by grommets so it won't commnunicate operating noise to the cabinet.

The washing unit-which includes an outer plastic tub that holds the wash water, the rotating stainless steel drum, the drive motor, and concrete counterweights-is suspended with two springs at the top and four shock absorbers at the bottom of the cabinet. The springs are fastened with plastic elements to damp sound.

The feet are molded of two materials, first polypropylene and then, in the same tool, thermoplastic elastomer. The design makes for good traction and damps the transfer of energy from the machine to the floor.

Structural parts were designed with sound reduction in mind. Thielemann said. Sheet metal parts have features like embossing in the side panels and a rounding of the front panel intended to retune natural frequencies to reduce vibration. Other parts are reinforced with ribs.

There is even extra glazing on the window through the door to inhibit the noise of the splashing in the wash tub.

According to Thielemann, the washer was brought to such a low noise level with design elements like these that further sound damping, such as isolating layers inside the panel, was deemed unnecessary.

There are two Duet washers, one with a list price of$999 and the other at $1,319. As you'd expect, they differ in some of their features. One spins at 900 rpm, the other at 1,100, for instance. The higher price brings extra cycles, including one for wool and another for silk.

The prices are more than double Whirlpool's median. The company lists 22 full-size washing machines on its Web site. They start at $249, and half of them are priced under $400.

The washing machine has an unusual design for the U.S. market. It loads from the front, like the usual clothes dryer. A front leader is a popular configuration in Europe, and the Duet is made in Schorndorf, Germany, where the design is familiar. Common wisdom among marketers in the United States says that people don't want to bend to load the washing machine, so the Duet's configuration makes it a rare bird in North America.

There is an upside to a front-loading washer, though. According to Whirlpool, the Duet will use only about a third of the water and electricity of a standard top-loading washer. The company claims the washer can save about $150 a year in utility costs. Also, because laundry tumbles in the drum, there's no agitator to stress the fibers in clothes.

To make a Duet, the washer has a companion dryer that looks almost identical. The dryer, which is made in Marion, Ohio, is also designed for quiet operation and retails for more than $800. In fact, you can order one through the Whirlpool Web site, if you want, for $819. It tops a list of 15 models, starting at $229.

The pair can be mounted on pedestals, which are sold separately. They raise the machines off the floor by about a foot, so that you don't have to bend your back as much. With the pedestals, the pair could go for somewhere around $2,300.

Even with savings on the electricity bill, that may sound like a lot to pay for something that washes your clothes. But for some people, the value is worth it. Remember, after all, you get to keep it quiet.

It may seem like a lot to pay, but for some people the value is worth the price.

The Harmony vacuum cleaner (top) is kept quiet by aerodynamics and a sealed motor. Three layers of insulation (above) and a rubberized motor suspension (far right) are sound-suppressing features of Bosch dishwashers. A suspended washing unit and a pump that doesn't have to strain help the Duet laundry pair (right) hold the noise down.

Copyright © 2004 by ASME
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