Acoustic locators were a means of detecting and tracking targets. The Finnish military acquired these devices between 1939 and 1943, when the air defence branch had no radar at its disposal. Acoustic locators were used in Helsinki. They were removed from service in the 1950s.

The acoustic locator made it possible to obtain audio observations of aircraft at a distance of 10–15 km. The acoustic locators thus functioned as “giant ears”, helping to determine the direction and altitude of aircraft.

Acoustic locators used by Finnish anti-aircraft units:

Acoustic locator m/39 Goerz

Made in Austria

Acoustic locator m/40 Tepas

Made in Belgium

Acoustic locator m/42 RRH

Made in Germany

RRH = Ringrichtungshörer
(In the yard in front of Puustelli)

Russian acoustic locator m/42

Made in the Soviet Union

(In the yard in front of Puustelli)

Acoustic locator m/43 Strömberg

Made in Finland

(In the Helsinki Hall)