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“acoustical surveillance”
Any of various military techniques that involve the use of sound-detection devices to obtain information for intelligence purposes: The members of the intelligence team of the national army used special equipment for acoustical surveillances in order to detect underground tunnels and shafts which the revolutionaries might have been using.
This entry is located in the following unit:
acous-, acou-, acouo-, acoustico-, acouto-, acousti-, -acousia, -acousis, -acoustical, acu-, -acusis-, -acusia
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