The sonar measuring beam

The acoustic velocity in a cavern depends on the density, the composition and the charactistics of the medium existing in the cavern.

The acoustic velocity and the measuring frequency determine the wavelength. The wavelength and the size of the survey sensor affect the angle of spread of the measuring beam.

The angle of beam spread is defined as being the point at which the echo signal has decreased by 50% (-6dB). This refers to both the left and right side of the measuring axis. The true angle of beam spread is therefore twice as big.

The specifications of the angle of beam spread are true only if the measuring signal strikes the cavern wall also between the points defined above. In order to ensure that the indicated angle of beam spread is maintained it is necessary to have optmium control at every individual measuring point. If this is not the case (in other sonar systems the parameters for a 360° scan are constant) the angle of beam spread is significantly higher!

If there is only one constant measuring frequency available (as is the case in other sonar systems), the angle of beam spread is variable and alters continuously depending on the acoustic velocity. Moreover, the characteristics and propagation conditions for the ultrasonic beam change according to the effects of temperature and pressure.

In SOCON systems as the frequency can be chosen it is possible to adjust the wavelength to suit the medium in the cavern; the highest possible measuring frequency is applied and adapted to the job to be carried out.

• A high measuring frequency decreases the angle of beam spread!
• The affects of temperature and pressure, which affect the ultrasonic ceramic unit, are compensated!
• Every measuring point is measured several times, checked, correlated, the energy adapted to the reflection conditions and then optimized.