Signal-to-Noise Criteria

The figure of merit for a sonic system of measurement that utilizes the generation, transmission, and reception of sound is defined as the maximum allowable transmission loss. This loss is derived from the sonar equation, which simply states that the received signal is equal to the background noise plus a measurement requirement, where the measurement requirement is set by the particular measurement under consideration. This method is not unique to sonics and may be applied to radar, astronomy, and communication theory. The advantage of the sonar equation that underlies the figure-of-merit computation is the fact that it permits quantitative comparison of various measurement schemes 

AS Averaged measurement parameter PSL Processed signal level 

DG Receiving-transducer directional gain NL Background noise level 

FIGURE 5-1 Elementary sonic-transmission scheme for measuring flow- 

Received Signal Level = Background Noise + Measurement Requirement. (5.1) 

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Signal-to-noise criteria are commonly employed as part of peak picking algorithms. 

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