Dive_Man_ChangeA

APPENDIX 1A — Safe Diving Distances from Transmitting Sonar 1A-3 helmet. In-water hearing occurs by bone conduction—sound incident anywhere on the skull is transmitted to the inner ear, bypassing the external and middle ear. In- gas hearing occurs in the normal way—sound enters the external ear canal and stimulates the inner ear through the middle ear. 1A-4.2 Directions for Completing the Sonar Diving Distances Worksheet. Follow the 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 particular situation. Step 1. Diver Dress. Identify the type of diving equipment—wet-suit un-hooded; wet-suit hooded; helmeted. Check the appropriate entry on step 1 of the worksheet. Step 2. Sonar Type(s). Identify from the ship’s 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. Step 3. 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. NOTE If the type of sonar is unknown, start diving at 600–3,000 yards, depending on diving equipment (use greater distance if helmeted), and move in to limits of diver comfort. Step 4. Distance to Sonar. Determine the distance (yards) to the transmitting sonar from place of diver’s work. Enter the range in yards in step 4 of the worksheet. Table 1A-1. PEL Selection Table. SONAR DIVER DRESS: All except AN/SQQ -14, - 30, -32 AN/SQQ -14, -30, -32 Unknown Sonar Wet suit - Un-hooded Table 1A-3 Table 1A-6 Start at 1000 yards and move in to diver comfort Wet suit - Hooded Table 1A-4 Table 1A-6 Start at 600 yards and move in to diver comfort Helmeted Table 1A-5 No restriction Start at 3000 yards and move in to diver comfort