Diverse industrial processes can be monitored by tracking changes in a fluid media. Having inline nondestructive information about the state of the process permits to have optimal results at reasonable costs. The suitability of low-power-ultrasound techniques has been widely investigated. However, sometimes this techniques have a poor signal-to-noise ratio or excessive sensitivity to temperature changes. In the present work, multiple-scattering of an ultrasonic signal is generated to enhancing the process-tracing ability. A pulse-echo system is used. The acoustic signal travels through a rod array, which is immersed in the changing medium. Useful information is taken from the echoes correlation. As a test case, this system has been proved for tracing milk coagulation, which is necessary in the cheese-manufacturing process