Figure 4.1: Example of an absorption spectrum. Source: [27].

The solution to this problem is provided by the resonator method. The effective propagation path is extended by multiple reflections between the transducers. The transducers are mounted in fixed positions and permit only adjustment of their parallel alignment. At discrete frequencies determined by the properties of the substance, a standing wave is established in the liquid.

4.2.1 The Ideal and the Real Resonator

Figure 4.2: Ideal resonator cell.

Original mathematical notation is preserved in the extracted image assets.