The Ultrasound installation consists of two facing parabolic
mirrors placed about 20 meters (the longer the better) from
each other. In the focal point of each mirror is a speaker
and a small LED-light. The very high pitched sine wave sound
played through the speakers create a kind of sound beam between
the mirrors. In optimal accoustic conditions the sound is
heard only between the mirrors, not elsewhere in the space.
The pitch of the sound coming out of one of the speakers
is about 16.000 Hz while the pitch of the sound coming out
of the other speaker is moving randomly between 12.000 Hz
and 20.000 Hz. This random movement of the pitch is caused
by a geiger meter measuring the constantly changing background
radiation of the air in the exhibition space.
Besides the sounds coming from the speakers a spectator standing
between the mirrors can hear a third sound
which frequency is the difference of the two above mentioned
frequencies. This modulation sound is coming from all
around, its source cannot be defined. This phenomenon together
with the two other high pitched sounds somewhat
distorts the spectators perception of space.
This installation was made in 1996 for Manifesta 1 -biennale
in Rotterdam and has appeared at shows in Tampere
(1997), London (1997),
and Hasselt (2004).
It is part of Kiasma's
(Finnish Museum of Contemporary Art) collection.