~e; internet-sound of music

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Listening to the internet reveals best connections

http://www.newscientist.com/news/news.jsp?id=ns99993112
 
19:00 27 November 02
 
Exclusive from New Scientist Print Edition
The World's No.1 Science & Technology News Service 

The reliability and strength of internet connections can be assessed by 
listening to the sounds they make, according to Chris Chafe, a cellist 
and director of the Center for Computer Research in Music and Acoustics 
at Stanford University in California.

This will be music to the ears of those developing the next generation 
of interactive internet technologies, like telesurgery, which need 
excellent connections. Telesurgery involves a surgeon using video 
screens to guide a remote robot arm to perform intricate operations. 
The robot and patient could be on the other side of the world, so the 
patient's life depends on constant and reliable connections.

To check the quality of an internet connection, engineers "ping" a data 
packet to a remote computer, which bounces it back like an echo. This 
reveals the latency of the connection, or how long it takes for a round 
trip, and the variation of this over time is known as the jitter. But 
pinging cannot reveal the detailed subsecond behaviour of the jitter, 
and this is the timescale that is important in interactive applications 
like telemedicine.

Chafe wondered if variations in jitter could be converted into a 
musical form. A musician can easily hear small changes in the tuning of 
a guitar string, so Chafe decided to model internet connections as 
guitar strings - twanging them to reveal subtle characteristics missed 
by pinging.


Pitch bend


Plucking a guitar string sets up standing waves of a certain frequency, 
determined by the length and tension of the string. Tighten or loosen 
the string, and you change the frequency and hence the pitch of the 
note. To simulate a string being plucked, Chafe and his team repeatedly 
sent a short sound pulse across a connection.

The time a pulse took to make the round trip depended on the state of 
the network. Say a pulse arrived at one end every 10 milliseconds. When 
fed into a loudspeaker and if the connection was good, this would emit 
a synthesised note of about 100 hertz - around an octave-and-a-half 
below middle C. The longer the transmission time, the lower the pitch 
of the note produced.

This gives a qualitative way of monitoring an internet connection. 
Sudden loss of sound can reveal a break in the network connection or 
missing packets of data. "It's like having your CD player hiccup, or an 
MP3 player that stalls," says Chafe. Most important, the sound 
accurately reveals the jitter. If the latency varies over time, so does 
the pitch. "Musically speaking that would be like pitch bends, or 
vibrato," he says.
 
Drum skin


Chafe reckons the technique could be used as an audible check of the 
health of a network connection before embarking on critical 
telesurgery, where minute changes in network delay could be dangerous.

He also speculates that his technique could help monitor the complex 
array of network connections on the Grid, the nascent network of 
academic supercomputers designed to provide massive computing power for 
tackling some of science's upcoming big problems.

But simulating a guitar string would not be suitable for a 
two-dimensional network like that described by the Grid. Instead, says 
Chafe, you would need to simulate a stretched membrane, such as a drum 
skin.

 
Anil Ananthaswamy, San Francisco
http://www.newscientist.com/news/news.jsp?id=ns99993112

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