1A-10 Change A
U.S. Navy Diving Manual—Volume 1
Example 3: You are planning a 98 fsw dive for 35 minutes using the MK 21 at a dive site which is 3000
yards from an AN/SQS-53C sonar. The duty cycle for the AN/SQS-53C 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
Helmeted
X
2. Type(s) of sonar: AN/SQS-53C
3. PEL Table 1A-3
; 1A-4
; 1A-5 X ; 1A-6
4. Range(s) to sonar (yards): 3000
5. Estimated SPL at range(s) in step 3 (from table/column in step 3): SPL1 = 181 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
6
dB
Reminder: 0 if not helmeted, see table in instructions if helmeted.
7. Corrected SPL (Step 5 minus Step 6) SPL1 181 – 6 = 175 dB
8. Estimated PEL at SPL (from table/column in step 3 of the appendix): PEL1 = 50 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 35 minutes is permitted because the PEL is 50 minutes.
Figure 1A-4. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example).
