NAVY DEPARTMENT 
OFFICE OF THE CHIEF OF NAVAL OPERATIONS 
Washington 25, D. C. 
SONAR - DETECTOR OF SUBMERGED SUBMARINES 
This publication was prepared by Lt. Cdr. A.P. Hilar, USN, Sec- 
tion Op413C4 of the Office of the Chief of Naval Operations and given to 
the Navy Office of Public Information for release to the Press on 6 April 
1946. 
The information contained herein indicates the extent to which 
Sonar has been declassified and may now be publicized. 
Copies are being sent to those participants whose names have 
been submitted to the originating office and appear in this publication. 
Upon request by any of the listed activities, additional copies will be fur- 
nished for distribution to any non-listed activity who participated in the 
Sonar program. 
The purpose of this distribution is to provide security guidance 
to activities who may wish to publicize their own wartime Sonar program. 
Articles which may be prepared by any of the above activities 
and which are not clearly within the confines of this publication, should 
be submitted to the Navy Department for clearance. 
i A-2405 
