Filtering considerably affects the quality of the signal.
- A 5 MHz probe is used. Although 5 MHz is the central frequency of the probe, in fact a range of frequencies creates the beam
- On the A-Scan, the signal from the SDH is at 80% FSH and the background noise is up to 5% FSH
- A 5 MHz filter is applied cutting the useless high and low frequencies
- On the A-Scan, the signal from the SDH is at 80% FSH but the background noise is down to less than 1% FSH
In General, the filter is chosen in function of the central frequency of the probe. But in specific applications, no filter or a filter meant for another frequency can give better results.