Standard_Test_Procedure_For_Determining_The_Acoustic_Signature_of_Underwater_Breathing_Apparatuses.pdf

Acoustic Signature Test Procedure 24 April 2007 NSWC-PC Procedure PCPUBA-A-001

Standard Test Procedure for determining the Acoustic Signature of Underwater Breathing Apparatuses

NAVAL SURFACE WARFARE CENTER, PANAMA CITY

24 April 2007

PCPUBA-A-001

Acoustic Signature Test Procedure 24 April 2007

Naval Surface Warfare Center, Panama City, Code E53

Standard Test Procedure for determining the Acoustic Signature of Underwater Breathing Apparatuses

24 April 2007

Facility: Acoustic Test Facility, NSWCPC Water: Fresh Depth: 25 feet of fresh water (ffw) Visibility: in excess of the depth Water Temp: 55-85°F

PURPOSE:

The US Navy does not currently have an acoustic requirement for UBAs. However, since low noise is a desirable trait of military breathing apparatuses, it is desirable to characterize the acoustic signature of Underwater Breathing Apparatuses (UBA). The purpose of this test is to determine the acoustic signature of a UBA.

METHOD:

The NATO specification NATO AMP-15 (formerly NATO STANAG 1158) will be used for guidance in conducting the test. In addition, an off-gas/venting signature for each UBA will be measured. This will be accomplished by manually adding gas to the UBA breathing loop so the UBA vent valve is activated on exhalation.

PROCEDURE:

1. All testing will be conducted at the acoustic test facility located at Naval Surface Warfare Center, Panama City.

2. A hydrophone capable of measuring the frequencies identified in NATO AMP-15 (1-100,000 Hz) will be mounted to an articulating arm that can be lowered and raised to the proper depth with consistency.

The arm shall be lowered within 0.5 to 1.0 meter from the bottom.

3. A reference device will be mounted to the arm that allows the diver to accurately locate himself the correct distance from the hydrophone. This device can be a length of cord attached to the articulating arm with a knot tied at the proper distance from the hydrophone.

Acoustic Signature Test Procedure 24 April 2007

4. A device to allow communication from the top side personnel to the diver will be lowered into the test pond.

5. When ready, the diver with a UBA will enter the water and proceed to the hydrophone. Once on the bottom, the diver will maintain a kneeling position and breathe the UBA until it has reached a steady state condition. For electronically controlled UBAs, this will occur when the sensors have reached the UBAs setpoint for the depth (i.e., ~0.75 pO2 for Mk16 Mod0,1,2&3 @ less than 34 ffw). For mechanical UBAs without pO2 monitoring, time to steady state condition must be inferred from unmanned testing data.

6. The diver will then position himself relative to the hydrophone using the reference device provided where several measurements will be taken as follows:

30-centimeter test resting (~2 min 45 sec):

a. The diver will position himself facing the hydrophone such that his mouthbit/barrel valve is at the same depth as the hydrophone and is 30 cm from the hydrophone. (~30 secs)

b. Once in position, the diver will give the OK sign. Using the communication device, the topside personnel will indicate to the diver that the test is beginning. The diver will maintain his position and breathe the UBA normally for approximately 30 seconds. Topside personnel will indicate to the diver that the test has ended. (~45 secs)

c. While maintaining position, the diver will rotate himself 90 degrees counterclockwise maintaining 30 cm between the mouthbit/barrel valve and the hydrophone. Repeat step 6b.

(~45 secs)

Acoustic Signature Test Procedure 24 April 2007

d. While maintaining position, the diver will rotate himself 180 degrees clockwise maintaining 30 cm between the mouthbit/barrel valve and the hydrophone. Repeat step 6b.

(~45 secs)

1-meter test resting (~2 min 45 sec):

e. The 1-meter test is the same as the 30 centimeter resting test except that the diver is positioned 1 meter from the hydrophone. Repeat steps 6a-6d at 1 meter

30-centimeter test working (~5 min 45 sec):

f. The working test is the same as the 30 centimeter resting test except that the diver will swim rapid laps around the pond area for 3 minutes to raise the breathing rate prior to positioning himself with the hydrophone. Repeat steps 6a- 6d.

1-meter test working (~5 min 45 sec):

e. The 1-meter test is the same as the 30 centimeter resting test except that the diver is positioned 1 meter from the hydrophone and the diver will swim rapid laps around the pond area for 3 minutes to raise the breathing rate prior to positioning himself with the hydrophone. Repeat steps 6a-6d at 1 meter.

7. While maintaining a distance of 1 meter, the diver will inhale on the UBA while adding gas with the manual gas addition valve. The diver will stop adding gas when he stops inhaling. The diver will exhale which should cause the UBA vent valve to activate and vent gas from the UBA. The acoustic signature of the UBA with venting gas will be measured. This step should be repeated again for each position indicated in steps 6c and 6d.

8. Diver exits water.

9. A different diver and UBA combination will enter the water and repeat steps 5-8.

Acoustic Signature Test Procedure 24 April 2007

MODIFICATIONS TO PROCEDURE:

The diving supervisor and/or test director may modify this procedure during the diving evolution for safety or collection of data.

Document revisions can be accomplished by contacting Naval Surface Warfare Center, Panama City, Code S13 with a request to change.

Changes will be evaluated by a Code S13 representative and if approved the change will be incorporated and a revision will be issued.

REPORT:

A test report will be provided by the acoustic test facility in accordance with paragraph 603 of NATO AMP-15, except that the calculation in step 603g will not be performed, instead all data will be provided and calculations made separately. This will keep the report unclassified.