Time-Frequency Detection: Application to Sub-Bottom SONAR

November 2000

introduction

Figure 6

Figure 6

Figure 6: 3-D Sonogram of a Parasound echo.
The sonogram was calculated in a frequency band from 2 to 7 kHz,
the time axis starts with the first break.
Later returns from the sub-bottom sediments have lost energy
and shift towards lower frequencies.