APPENDIX A: HAW-15* ACOUSTIC PROJECTOR TESTS 
AT LAKE PEND GREILLE, IDAHO 
20-22 May 1980 
by 
TE Stixrud 
SUMMARY 
The newly-developed HAW-15 sound projecter was operated at Lake Pend Oreille 
Facility for 17 hours at a depth of 500 ft and at intermediate depths for shorter periods of 
time. The unit exhibited no degradation of performance during this evaluation. It required 
an increase of input power as depth and internal pressure increased in order to offset the 
increased “‘windage™ loss of the moving parts. Most data were recorded at full power output. 
The source level of 171 dB re 1] wPa at 1 m at 15 Hz was computed by the volumetric 
displacement of the pistons and the characteristics of the medium. 
INTRODUCTION 
The HAW-15 has recently been developed by HA Wilcox, of NOSC, with IED funds. 
Its two opposed pistons are driven through a unique variable throw mechanism by means of 
asmall electric motor. The motor drives an intermediate flywheel. The flywheel stores 
energy from the pistons during one part of the cycle and returns it to the pistons during the 
other part. When the variable piston throw is set at zero, friction is the only system load and 
the motor-driven flywheel can be started at any operating depth. The acoustic source level 
can then be set as desired within the design limits. Frequency is controlled by means of the 
motor speed, 15 Hz being the nominal design value. 
The projector satisfied all expectations during the initial verifications at Transdec. 
This prompted DL Carson of this Center to provide funding for extending the evaluation to 
the much greater depth of 500 ft and a longer operating time at the Lake Pend Oreille 
Facility. 
PREPARATION 
A 550-ft cable was borrowed from Code 5314. Figure Al shows how this cable was 
connected. 
The transducer was modified as follows: 
1. The cover plate was provided with guide pins and handles. 
2. A S-psi differential pressure transducer was installed. 
3. The V-belt end pulley drive system was replaced by a more efficient Berg 
gear and chain drive. 
Grease seals were installed on the bearings and all bearings were lubricated. 
= 
5. Adapters were installed for attaching an air tube for No pressure compensation 
and fcr attaching an oil tube from an external oil bladder to the internally 
mounted pressure transducer. 
6. Two adapters to couple nitrogen flasks to the scuba regulator were made. 
*In this appendix the subject nonzesonant acoustic projector is referred to as Model HAW-15. 
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