APPENDIX 1A Safe Diving Distances from Transmitting Sonar
Change A 1A-1
A P P E N D I X 1 A
Safe Diving Distances from
The purpose of this appendix is to provide guidance regarding safe diving
distances and exposure times for divers operating in the vicinity of ships transmit-
ting with sonar. Table 1A-1 provides guidance for selecting Permissible Exposure
Limits Tables; Table 1A-2 provides additional guidance for helmeted divers.
Tables 1A-3 through 1A-5 provide specific procedures for diving operations
involving AN/SQS-23, -26, -53, -56; AN/BSY-1, -2; and AN/BQQ-5 sonars.
Table 1A-6 provides procedures for diving operations involving AN/SQQ-14, -30,
and -32. Section 1A-5 provides guidance and precautions concerning diver expo-
sure to low-frequency sonar (160-320Hz). Contact NAVSEA Supervisor of Diving
(00C3B) for guidance on other sonars. This appendix has been substantially
revised from Safe Diving Distances from Transmitting Sonar (NAVSEAINST
3150.2 Series) and should be read in its entirety.
Chapter 18 of OPNAVINST 5100.23 Series is the basic instruction governing
hearing conservation and noise abatement, but it does not address exposure to
waterborne sound. Tables 1A-3 through 1A-6 are derived from experimental and
theoretical research conducted at the Naval Submarine Medical Research Labora-
tory (NSMRL) and Naval Experimental Diving Unit (NEDU). This instruction
provides field guidance for determining safe diving distances from transmitting
sonar. This instruction supplements OPNAVINST 5100.23 Series, and should be
implemented in conjunction with OPNAVINST 5100.23 Series by commands that
The Sound Pressure Level (SPL), not distance, is the determining factor for estab-
lishing a Permissible Exposure Limit (PEL). The exposure SPLs in Tables 1A-3
through 1A-6 are based upon the sonar equation and assume omni-directional
sonar and inverse square law spreading. Any established means may be used to
estimate the SPL at a dive site, and that SPL may be used to determine a PEL.
When the exposure level is overestimated, little damage, except to working sched-
ules, will result. Any complaints of excessive loudness or ear pain for divers
require that corrective action be taken. Section 1A-5 provides guidance for diver
exposure to low-frequency active sonar (LFA), which should be consulted if expo-
sure to LFA is either suspected or anticipated.
This appendix does not preclude the operation of any sonar in conjunction with
diving operations, especially under operationally compelling conditions. It is
based upon occupational safety and health considerations that should be imple-
mented for routine diving operations. It should be applied judiciously under