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The
experimental use of listening equipment's of foreign make in the late 1920's
did not satisfy the Dutch army. The nature of the complaints has not been
found in writing. But one may safely suppose that the complaints were caused
by the clumsiness of the equipment affecting transport, installation and
accuracy of measurements.
This caused loss of time which additionally was increased by the required
cooperation with the other required equipment. Furthermore the acoustic
properties were far from ideal due to e.g. mechanically caused noise during
use of the equipment.
The study of this complex was the subject of an assignment of the Committee
to the Measurements Building. A number of details and the progress of
this first order are still known. Therefore the subject will be discussed
to some extent to illustrate the working method of the Measurements Building.
According to still existing documents a Czechoslvakian equipment of Goerz
has been investigated. Because this equipment contained fundamental deficiencies
it was decided to construct a new prototype. This development was subsequently
compared with three different listening equipments among which a part
of the Goerz equipment.

Doppelt Richtungshörer, manufacturer
Askania, Germany
(full size 285 KB)
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Half of the equipment by
Goerz, Czechoslovakia
(full size 285 KB)

Equipment by Barbier, Bénard
and Turenne, France
(full size 214 KB)
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