With ever-increasing levels of noise pollution in our lives there is an urgent need to combat it. A scientist, Prof. Selwyn Wright at the University of Huddersfield in the United Kingdom, has developed a device for blocking out sound electronically, both
indoors and outdoors. It is called the 'electronic controlled acoustic shadow system' and creates a 'silent shadow' that can mask most sounds over a wide area.
The basic principle behind the device is simple: a computer generates the same noise as the problem sound but reverses the sound waves, This is called replica. A bank of microphones picks up the offending noise and feeds it into the computer which then analyses the sound and broadcasts its exact electronic opposite via further bank of loudspeakers, thus canceling out the original sound to produce ...silence!
Although sound blocking devices using this technology have been around for some years they have been only capable of working indoors and over a small area for example in aircraft cockpits. Conventional methods of reducing low frequency sound over large areas involve building heavy and expensive structures to provide a solid barrier.
Computer modeling has demonstrated that 'shadows' such as those created by the 'ecass' can be superior to those generated naturally by solid barriers. Detailed analysis predicts that EEP shadows (more than 100 decibels) are possible.
For the technically inclined, this facility measures 6m x 6m x 5m; the eight channel system is based on a Texas instruments tms320c32 processor using a two tap filter and a circular buffer technique to implement the delayed version of the update algorithm. This allows easy algorithm implementation in software and significantly reduces computation time for a large number of channels a 16 - input, 8 - output. PC 16108 provides a 12-bit interface with the external equipment. This board contains three selectable levels of gain: 1,10,100.
Thus as scientists use noise against noise pollution, there is something to cheer about…. Ssssh, not so loud !!
On second thoughts.....
| "The ability to quote is a serviceable substitute for wit " -W.Somerset Maugham |
| " We are what we repeatedly do. Excellence then, is not an act, but a habit." -Aristotle |
