Lesson 20 - Passive Figure of Merit

If FOM < TL, what does that tell us about probability of detection?

Less than 50% probability

If FOM > TL, what does that tell us about probability of detection?

Greater than 50% probability

What does FOM help to predict?

Range

Higher FOM = ?

Greater detection range

What is directivity index?

SONAR’s ability to block out sounds coming from directions other than the direction of interest

What does a larger directivity index mean?

Improved detection/FOM

What is the definition of detection threshold?

Signal minus the nose required inboard of the hydrophone array for an operator using installed equipment to detect a target 50% of the time.

What does a smaller/more negative detection threshold mean?

Improved detection / FOM

How can we improve the FOM?

Look at the equation

• Increase source level

• Decrease noise level

• Increase directivity index

• Decrease detection threshold