Singing Alarms Could Save the Blind.
If you cannot see,you may not be able to find your way out of a burning building-andthat could be fatal .A company in Leeds couldchange all that______(51)directional
sound alarms capable of guiding you to the exit.
Sound Alert,a company______(52)the University of Leeds,is installingthe alarms in a residential home for______(53)people in Sommerset and aresource centre for the blind
in
Cumbria.______(54)produce a wide range of frequencies that enable the brain todetermine where the______（55)is coming from.
Deborah Withington of Sound Alert says that the alarms use most of thefrequencies that can be______（56)by humans."It isa burst of white noise ______(57)people say
sounds like static on the radio,"she says."Its life-saving potentialis great."
She conducted an experiment in which people were filmed by thermal-imagingcameras trying to find their way out of a large______(58)room. It______(59)themnearly four
minutes to find the door______(60)a sound alarm,but only 15 seconds with one.
Withington studies how the brain______(61)sounds at the university. She saysthat the _______(62)of a wide band of frequencies can be pinpointed more easilythan the
source of a narrow band .Alarms______(63)the same concept have already beeninstalled on emergency vehicles.
The alarms will also include rising or falling frequencies to indicate whetherpeople should go up______(64)down stairs.They were______（65)with the aid of a large grant
from British Nuclear Fuels.

56._________

A.watched

B.produced

C.learnt

D.heard