APPENDIX 1A — Safe Diving Distances from Transmitting Sonar
Change A 1A-9
Example 2: You are planning a routine dive for 75 minutes using wet-suited divers without hoods at a dive
site which is 1000 yards from an AN/SQS-23 sonar. The SPL was measured at 185 dB. The duty cycle for
the AN/SQS-23 sonar is unknown. Is this dive permitted? Provide justification for your decision.
SONAR SAFE DIVING DISTANCE/EXPOSURE TIME WORKSHEET
1. Diver dress:
Wet Suit - Un-hooded
X
Wet Suit - Hooded
Helmeted ______
2. Type(s) of sonar: AN/SQS-23
3. PEL Table 1A-3 X ; 1A-4
; 1A-5 __; 1A-6
4. Range(s) to sonar (yards): 1000
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL = 185 dB
Reminder: If range is between two values in the table, use the shorter range.
If the SPL is measured at the dive site, use the measured value.
6. Depth Reduction
0
dB
Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6) SPL1 185 – 0 = 185 dB
8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 170 minutes
9. Duty Cycle Known: Yes ______ (do step 9); No
X
(stop)
Adjusted PEL for actual duty cycle
Actual DC % = 100 × _____ sec. (pulse length / _____ sec. (pulse repetition period)
Actual DC % = ______
Adjusted PEL = PEL (from step 8) ___ min. × 20 / actual duty cycle (%) ___ = ___ min.
Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes _____ (do step 10); No X
(stop)
Sonar 1:
DT1 =
(Desired dive duration)
PEL1 =
(from Step 8 or 9, as applicable)
DT1/PEL1 =
.
Sonar 2:
DT1 =
(Desired dive duration)
PEL1 =
(from Step 8 or 9, as applicable)
DT1/PEL1 =
.
ND = ____ + _____ = ____ (This is less than 1.0, so dive is acceptable and may proceed.)
Reminder: The Noise Dose must not exceed a value of 1.0.
The dive time of 75 minutes is permitted because the PEL is 170 minutes.
Figure 1A-3. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).
