APPENDIX 1A — Safe Diving Distances from Transmitting Sonar
Change A 1A-11
Example 4: You are planning a routine dive for 120 minutes using wet-suited divers with hoods at a dive site
which is 200 yards from an AN/SQS-53A sonar and 120 yards from an AN/SQS-23 sonar. The AN/SQS-53A
sonar is transmitting an 800 msec pulse (0.8 sec) every 20 seconds. 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
Wet Suit - Hooded
X
Helmeted
2. Type(s) of sonar: AN/SQS-53A and AN/SQS-23
3. PEL Table 1A-3
; 1A-4 X ; 1A-5
; 1A-6
4. Range(s) to sonar (yards): 200 (from SQS-53A); 120 (from SQS-23)
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL1 = 201; SPL2 = 196
(per reminder, use SPL for 112 yard range)
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 201 – 0 = 201 dB; SPL2 196 – 0 = 196 dB;
8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 143 min; PEL 2 = 339 min
9. Duty Cycle Known: Yes
X
(do step 9); No
(stop)
Adjusted PEL for actual duty cycle
Actual DC % = 100 ×
0.8
sec. (pulse length / 20
sec. (pulse repetition period)
Actual DC % = 4
Adjusted PEL = PEL (from step 8) 143 min. × 20 / actual duty cycle (%) 4 = 715 min.
PEL1 = 715 minutes; PEL2 = 339 minutes
Reminder: Do not adjust the PEL if duty cycle is unknown.
10. Multiple Sonars: Yes
X
(do step 10); No
(stop)
Sonar 1:
DT1 = 120 (Desired dive duration)
PEL1 = 715 (from Step 8 or 9, as applicable)
DT1/PEL1 = 120/715 = 0.17 .
Sonar 2:
DT1 = 120 (Desired dive duration)
PEL1 = 339 (from Step 8 or 9, as applicable)
DT1/PEL1 = 120/339 = .35 .
ND = 0.17 + 0.35 = 0.52 (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 120 minutes is permitted because the ND is less than 1.0.
Figure 1A-5. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).
