APPENDIX 1A Safe Diving Distances from Transmitting Sonar
helmet. In-water hearing occurs by bone conductionsound incident anywhere on
the skull is transmitted to the inner ear, bypassing the external and middle ear. In-
gas hearing occurs in the normal waysound enters the external ear canal and
stimulates the inner ear through the middle ear.
Directions for Completing the Sonar Diving Distances Worksheet.
steps listed below to determine Permissible Exposure Limits (PELs) for the case
when the actual dB Sound Pressure Level (SPL) at the dive site is unknown.
Figure 1A-1 is a worksheet for computing the safe diving distance/exposure time.
Figures 1A-2 through 1A-5 are completed worksheets using example problems.
Work through these example problems before applying the worksheet to your
Diver Dress. Identify the type of diving equipmentwet-suit un-hooded; wet-suit
hooded; helmeted. Check the appropriate entry on step 1 of the worksheet.
Sonar Type(s). Identify from the ships Commanding Officer or representative the
type(s) of sonar that will be transmitting during the period of time the diver is
planned to be in the water. Enter the sonar type(s) in step 2 of the worksheet.
PEL Table Selection. Use the Table 1A-1 to determine which PEL table you will
use for your calculations. For swimsuit diving use wet suit un-hooded tables.
Check the table used in step 3 of the worksheet.
For guidance for sonars not addressed by this instruction, contact NAVSEA
(00C32) DSN 327-2766.
If the type of sonar is unknown, start diving at 6003,000 yards,
depending on diving equipment (use greater distance if helmeted), and
move in to limits of diver comfort.
Distance to Sonar. Determine the distance (yards) to the transmitting sonar from
place of divers work. Enter the range in yards in step 4 of the worksheet.
Table 1A-1. PEL Selection Table.
-14, - 30, -32
-14, -30, -32
Wet suit - Un-hooded
Start at 1000 yards and move
in to diver comfort
Wet suit - Hooded
Start at 600 yards and move in
to diver comfort
Start at 3000 yards and move
in to diver comfort