[FoRK] Active Noise Suppression for PCs

Gordon Mohr gojomo at usa.net
Tue Mar 16 12:44:16 PST 2004


About 3 years ago I wondered to fork...
 > OK, why can't PCs use active noise suppression -- the
 > generation of matched anti-noise -- for masking the
 > annoying whirrs of fans and hard-drives?
[http://www.xent.com/FoRK-archive/2001.04/0158.html]

Finally, there's been some work here [via slashdot]:

http://tv.ksl.com/index.php?nid=5&sid=81082

# BYU Professor Trying to Make Office a Quieter Place
# Mar. 15, 2004
#
# On his way out of the office one day, Brigham Young University physics
# professor Scott Sommerfeldt shut down his desktop computer, printer and
# other equipment and "couldn't believe how quiet" the room had become.
#
# SALT LAKE CITY (AP) -- On his way out of the office one day, Brigham
# Young University physics professor Scott Sommerfeldt shut down his
# desktop computer, printer and other equipment and "couldn't believe how
# quiet" the room had become.
#
# "That made me aware of how much background noise we put up with," said
# Sommerfeldt, who has worked for NASA trying to make turbo jet engines
# run quieter.
#
# Sommerfeldt set about to find a way to drown out the whinny noise from
# built-in fans that cool computers and other electronic devices. He came
# up with an idea for a cheap noise-control unit that's built around its
# own fan.
#
# The new unit would take no more space than that of a conventional fan
# and add only about $20 to the cost of a personal computer, he said.
#
# The results of his design, made in collaboration with Pennsylvania State
# University acoustics graduate Kent Gee, were to be published Monday by
# the Noise Control Engineering Journal.
#
# Their noise-control unit consists of four tiny loudspeakers and
# microphones built into the case around a fan.
#
# The four microphones measure the fan's noises and signal a tiny
# microprocessor that drives the speakers, which make sound waves
# precisely canceling out the sound waves of the rotating fan blades. From
# the speakers come a sound pressure inverse to the pressure made by the
# fan, Sommerfeldt said.
#
# It's hard to think of loudspeakers creating silence. Sommerfeldt said it
# would be like placing conventional speakers in an air vacuum, where the
# speaker cones would vibrate but produce no sound.
#
# But Sommerfeldt hasn't achieved absolute quiet yet from his unit.
#
# "You can hear a distinct difference if the (noise-control) system is on
# or off," he said of the audible results so far.
#
# "It doesn't make it completely quiet, but it eliminates all of the tonal
# noise of the fan -- the whine of the fan. It takes that virtually
# completely out. You don't hear that any more, but you hear some other
# noise. We haven't made a quiet world yet, but it's noticeably better."
#
# The sound that remains is the whoosh of air moving through the fan, a
# noise made from the air molecules swirling over the fan's built-in ducts.
#
# "We're knocking out the whine" and working to get rid of the whoosh,
# Sommerfeldt said.
#
# His work for NASA was more challenging.
#
# Sommerfeldt said he made some progress reducing the roar of jet engines
# "but that's a very difficult problem" without an easy fix. The space
# agency dropped the project, he said.
#
# (Copyright 2004 by The Associated Press. All Rights Reserved.)
#


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