Body-wired headphones November 29, 2006
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Sony’s Tokyo research lab has found a way to connect headphones to portable music and video players without the need for fiddly wiring. They simply feed an audio signal straight through the listener’s body.
Existing wireless headphones use Bluetooth radio, but this means pairing two devices beforehand and is prone to interference from other equipment. Another approach – infra-red – relies on line-of-sight, which is rarely practical.
The new system uses the listener’s body as a capacitor that carries a tiny electrostatic charge. A music or video player sends a fluctuating signal to a conductive cloth pad – such as a wrist band – and this slightly charges the wearer’s body. A pair of conductive ear pads in the headphones pick-up the signal and rapidly convert it back into sound.
Just a few millionths of an amp flow through the wearer’s body, so there should be no nasty tingling effect. To convert the small charge into good quality audio, Sony uses a high frequency signal, which is digitally switched to carry data at 48 kilobytes per second. This is enough to deliver good quality, body-rocking stereo, the company says.
21st Century (21CN) phone network in UK November 29, 2006
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The first stage of a project to build one of the world’s most advanced telephone networks has been completed. The so-called 21st century network (21CN) is being built in the UK using Internet Protocol technology.
The massive upgrade, the first of its kind, will cost British Telecom £10bn and take until 2010 to complete.
It will open the way to new services as well as making existing services quicker and cheaper than before.
1,500 man years
The first person to use the new network was schoolgirl Laura Wess from South Wales.
The eleven-year-old spent a minute and a half chatting to the Right Reverend John Davies, the bishop of St Asaph.
She was chosen for the landmark call as she is one of the residents of Wick, near Cardiff, which is the first village to be upgraded to 21CN.
“Today marks a symbolic and momentous occasion for BT, the communications industry, for Wales and the rest of the UK as 21CN, over three years in the making, starts to become real for customers,” said Paul Reynolds, chief executive of BT Wholesale.
BT has so far rebuilt around 10% of its network, laid more than 2,300 kilometres of new fibre optic cable in South Wales and invested more than 1,500 man years in developing the systems to support the new network.
Customers in Cardiff, Bridgend and Pontypridd will be the next to be transferred. The upgrade does not require customers to have a new telephone or number and can be done without an engineer visiting the premises.
Voice, data, broadband and multimedia services will all be carried on the new network. It will allow for faster broadband speeds as well as opening the door for services not yet thought of.
Silent Aircraft design November 9, 2006
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Engineers from the University of Cambridge and the Massachusetts Institute of Technology have unveiled a radical design for a “silent aircraft”. The team says any noise from the concept aircraft, known as the SAX-40, would be “imperceptible” beyond the boundaries of an airport. It would also burn far less fuel than conventional planes.
The design is the result of three years’ work and includes both new and existing technologies.
Here, the BBC News website details some of the design’s key features.
1. AIRFRAME
Turbulent air around conventional aircraft creates a lot of noise |
The shape of the plane is what is known as a “blended wing” design. This hybrid design uses the wings of a conventional plane smoothly blended into a wide tailless body.
As turbulent airflow, generated by irregular surfaces, causes noise, the designers tried to make the airframe as smooth as possible.
The aerofoil shape of the body means that it also contributes to the aircraft’s lift, meaning it can make a slower approach on landing, again reducing noise.
The improved lift also means that the plane can do away with flaps on the wings, which are a major source of airframe noise on conventional aircraft.
Because the design does not need a tail, used to provide additional lift and stability on conventional craft, it also cuts down on turbulent airflow and noise from the back of the plane.
The design, made of lightweight composites, also improves the fuel efficiency of the craft whilst cruising.
2. ENGINES
The engines are embedded into the body of the aircraft |
The engines of the SAX-40 are embedded within the blended wing design with the air intakes on top. This means that the upper surface of the aircraft shields people on the ground from engine noise.
The engines are also mounted deep within the intake ducts, lined with mufflers, to maximise the noise absorption.
By embedding the three engines in the aircraft frame, it also reduces drag and therefore noise.
The “ultra-high bypass ratio turbofans”, as they are known, are also arranged in a novel way to minimise noise output.
Instead of having one large fan, they have three arranged side-by-side. The smaller fans means the noise from each one is easier to absorb with surrounding “acoustic liners”, or muffling materials.
3. EXHAUSTS
The exhaust system optimises the engines performance |
The output of the engines is channelled through what is known as a “variable area exhaust nozzle”.
This means that the cross sectional area of the exhaust can be changed to generate different amounts of thrust and to maximise the engine’s performance.
At take-off the exhausts would be open-wide to generate the maximum amount of thrust. Whilst cruising they would reduce in size to burn fuel more efficiently.
They can also be rotated, or “vectored”, to generate thrust in the optimal direction for take-off and landing.
The exhaust are also lined with “mufflers” to reduce the noise of the engines.
4. UNDERCARRIAGE
The landing gear of the SAX-40 is designed to minimise noise |
Turbulent air swirling around the undercarriage at take-off and landing are major sources of noise.
To reduce this, the SAX-40 would have fairings to cover the wheels and braking systems, creating as smooth a flow of air as possible. This could reduce the noise from the landing gear by up to 7dB.
However, by doing this it makes the landing gear more difficult to stow and service, and also makes cooling the brakes more difficult.
5. TRAILING WING EDGE
The trailing edge of the wings minimises turbulent mixing of air |
When turbulent air moving over the top surface of the wing shoots off the trailing edge it abruptly meets non-turbulent air. The result generates a huge amount of noise.
To minimise this, the SAX-40 would have “trailing edge brushes”, a series of long, thin protrusions off the back of the wing.
These allow a smoother transition between turbulent and non-turbulent air and could reduce trailing-edge wing noise by up to 4dB.
6. LEADING WING EDGE
The Airbus A380 uses the drooped design on the front of its wings |
The leading-edge of the wings are slightly drooped. These further help improve the lift of the aircraft, particularly at lower speeds.
To cut-down on the amount of noise generated by air whistling through a slat between the main wing body and the leading edge, the gap is covered in a flexible material.
The edges would be stowed whilst cruising for optimum performance
This drooped design is already being used on the Airbus A380
Source : BBC New
