Figure 1A-4. Sonar Safe Diving Distance/Exposure Time Worksheet (Completed Example)

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).