Gas turbine engines used in power generation and jet engines generate substantial noise from the combustion process, and the interaction of the expanding hot gases and the combustion chamber. Researchers have found that by using fuel injectors that are phased to release fuel at the correct time, the combustion pulses can be used to damp the system.
Read the full story on the ASME web site.
Researchers at MIT have won a grant to investigate the use of hydrophones to detect hurricanes and use the information to determine the wind speed.
Read the story on the MIT web site.
Researchers have found that the stereocilia, the tiny hair cells in the ear that convert vibrating air into electrical signals in the ear, are replaced every two days. Their finding could explain the reason why it takes two days to recover from exposure to loud music or noise.
Read the article on the New Scientist web site.
Researchers at Boston University have found that when feet are vibrated, people have less tendency to sway. They conducted tests by getting people to stand on a vibrating platform and found that people swayed several millimeters less than when the platforms were stationary.
Read the article on the New Scientist web site.
Piezotech, a company in Indianapolis, has been awarded a NIST grant of $2.5m to develop piezoceramic transducers that will produce ultrasonic sound that can be focused to destroy diseased tissue. The challenge is to design the devices that can fit inside body cavities!
Read the story on the NIST web site.
LMS International, a distributor of acoustic and vibration software, has an article about sound quality at Harley Davidson motorcycles.
At first, the notion of sound quality and HD seem at odds, because of their distinctive exhaust roar. However, engineers try to enhance some sounds such as the engine roar, and reduce other noises such as rattles and clicks.
Read the article on the LMS International web site.
An engineer at the University of Tel Aviv, pulled out the magnetron from a domestic microwave oven and has developed a drill that could one day replace the conventional dentists’ drill.
Read the story on the inScight web site.
The Millenium Bridge over the Thames was opened on 10 June 2000, but was closed three days later after complaints of people feeling “sea sick”. The problem was caused by the people walking synchronously. When people walked across the lightweight bridge it vibrated at its resonance frequency and people subconsciously adjusted their walking pace so that it matched the resonance frequency of the bridge, as this causes the least resistance to a person walking. However when several hundred people are all exciting the bridge at the resonance frequency, it causes the bridge to sway. Engineers at ARUP tested the bridge and analysed the data. The remedy was to install dampers to reduce the vibration.
Read more about this story on the ARUP web site.
Read the article on the BBC web site.
The hard disks inside every desktop and laptop are designed to emit low noise and generate, and also to be relatively insensitive to vibration.
Two important designs features that enable this are fluidic bearings and winglets on the head of the arm.
Hard disks were once made with tiny rolling element ball bearings, however nowadays almost all hard disks are made with fluidic (journal) bearings. These bearings are more reliable, quieter, generate less vibration, and cheaper than the ball bearings.
Another important design feature are the winglets on the end of the read / write head. The hard disks spin at 4200rpm or higher which causes the air to move. Small wings attached to the sides of the hard disk head enables the head to “fly” precisely above the rotating disk. This design makes the hard disk less sensitive to vibration.
BBC news has an article about the effects of low frequency sound. Church organs emit infra-sound which causes mood changes in the congregation. Elephants use infra-sound to communicate.
Read the story on the BBC news web site.