Jim McKevitt, 3M Acoustic Solutions, St. Paul, MN

According to a recent survey by Ipsos, consumers are happy with their washing machines, dishwashers, vacuums, and other appliances. They have only one complaint – noise. What’s more, the survey found that consumers are willing to pay a premium for a branded sound blanket such as ThinsulateTM Acoustic Insulation. Noise is as much an environmental pollutant as dust, lead powder, or any other airborne contaminant, but it is one that we can control.

Most respondents-68%-wanted sound reduction applied to dishwashers, followed by 58% for vacuum cleaners, 57% for air conditioners, 55% for washing machines, and 53% for clothes dryers. Next came refrigerators, lawn mowers, leaf blowers, power tools, hair dryers, blenders, microwave ovens, and coffee machines. Ipsos conducted the survey for 3M Acoustic Solutions to better understand consumer shopping habits for appliances. Of the respondents, 80% indicated noise reduction was “extremely/very influential” in the recent purchase or intended future purchase of a dishwasher.

Appliance noise primarily comes from motors, fans, and mechanical vibrations. Noise occurs when the motor vibrates rapidly enough to stir air molecules that generate a pressure or sound wave in the surrounding air.

The two types of noise that influence appliance design are airborne and structural.  The movement of large volumes of air and the use of high-pressure air cause airborne noise. Absorbers (non-wovens and foams) and barriers can control it.

Structure-borne noise is the acoustic (vibration) energy that structures transmit, such as plastic and metal structural parts. The impact of the sound waves causes the material to vibrate and transmit the sound to other areas. Sound waves are readily transmitted through rigid materials. Hard, solid materials such as wood, metal, or wallboard, transmit and sometimes amplify sound, while soft materials such as fabric or foam absorb the vibrations and stop sound from traveling.

To reduce noise, appliance manufacturers have relied on non-woven acoustic insulation materials, including fiberglass, remnants (felt, shoddy), and various synthetic insulation products. Traditional sound absorbers, however, have limitations such as weight, flexibility, handling and moisture resistance, and so forth.

Today’s insulations use new synthetic materials, manufacturing processes, and structures. Low density, highly compressible, cavity filling, and non-woven acoustic absorbers, such as 3M’s TC Series products, address most, if not all, of the shortcomings of older products. Sound waves enter easily into the materials, then loft and flow over a large surface containing fine and large fibers, which dissipate the energy into thermal energy. This sequence occurs because of the synthetic fibers in the insulation.

These new generation absorbers compress easily and conform to irregular surfaces, tight spots, difficult-to-reach areas, and irregular cavities such as those found in vacuums, dishwashers, and washing machines. When the sound path is in the lateral direction (plane of the material), compressing the material increases the energy dissipation and sound absorption properties.

The absorbers are ideal for novel designs in traditional appliances, including areas that have irregular shapes such as vacuum cleaner housings. For example, consider a space requiring insulation from 10 to 30 mm (0.39 to 1.18 in.). A traditional absorber package for this
application would require one or more materials, have a complex design, and occupy 7 to 25 mm (0.28 to 0.99 in.) of the maximum space.  Newer products that conform and compress let you make a single component, single part acoustic package that eliminates design restraints such as clearance and tolerance.

The synthetic materials are also naturally hydrophobic, which reduces the chance for mold, mildew, corrosion, and other odors.

Attachment is easy too. You can use a variety of methods such as pressure sensitive tape, spray adhesive, sonic welding, or thermal bonding. 

Today, some appliance manufacturers have reduced the noise level of their dishwashers to decibels in the mid 40s, the loudness of a quiet conversation between two people. Because they are so quiet, some manufacturers install lights on their dishwashers to indicate operation. R&D departments are working on new materials to reduce dishwasher noise levels even further so families can gather in the kitchen and converse without competing with noisy appliances.

* The Research firm Ipsos conducted online interviews for 3M, collecting 857 interviews from dishwasher/washing machine owners who either made their purchase in the last year or consumers who intend to purchase in the next two years. Respondents were 25 to 60 years old, home owners, and were the decision maker regarding home appliances.

3M Acoustic Solutions
www.3m.com

: Design World :

---

Filed Under: Appliance engineering + home automation

 

---