Tread pattern in tires determines radiated noise

Tires for vehicles have various tread patterns, usually to balance the amount of traction to the road surface during dry and wet weather. As most people know, a solid soft tyre has the greatest surface area in contact with the road and hence has the most amount of traction. The tread pattern allows water to escape when the tire is on wet roads.

When the tread is in contact with the road surface, volumes of air are formed between the road and the tread pattern in the tire, which is compressed as the tire rotates. The volumes of air are a network of small Helmholtz resonators that generate noise.

In addition, the interaction of the tread pattern with the road vibrates the body of the tire and causes the walls of the tire to radiate noise.

Read an article on tire noise by Stuart Bolton.

US mine hunter ships don’t use conventional propellors

I read an interesting article on the Naval Sea Systems Command web site that shows pictures of the propulsion system used on the US mine hunter ships. The ships use a Vertical Axis Cycloidal Propeller system designed and manufactured by a German based company, Voith Schneider. The Voith Schneider Propeller (VSP) not only eliminates the need for conventional props and rudders, it also eliminates the requirement for bow thrusters. This propulsion system makes the boats quieter than conventional propellor boats.

Read the full article here.

Endevco and Sandia Labs sign agreement

Endevco and Sandia have signed an agreement to develop high g accelerometers and recording devices for use in Emerging Threats missions.

Endevco is a manufacturer of accelerometers. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration.

Read the full article on their web site.

Vibration increases bone density

Researchers placed pigs on a gently vibrating platform for 20 minutes a day and found that the pigs’ bone density increased. Read the full article on the Nature web site

This therapy has also been used on astronauts returning from space. Read more here.

Univ of Texas develops software to predict noise and vibration in automobiles

The University of Texas has developed software to predict noise and vibration in automobiles. Automated Multilevel Substructuring (AMLS) was copyrighted in 2000. The software divides the model of a car into sub-structures and solves them independently. A model that originally would have had 1e6 DOFs, can be reduced into 20 levels of 10e3 DOFs.

Read the full story on the University of Texas web site.

MSC released MSC.Actran

MSC Software has partnered with Free Field Technologies of Belgium, to launch a vibro-acoustic software package called MSC.Actran.

The software uses finite element formulation for the acoustic elements. It can be used to model sound radiation, propogation (can handle non-uniform mean flow which makes it suitable for studying exhaust systems), enclosed sound fields, locally and non-locally reacting liners (suitable for modeling seats), sandwich panels (can handle constrained layer damping).

Read the description of the product on their web site (This is hard to find from their homepage)

Also read about the news story on Free Field Technologies web site.