Ultrasonic Distance-Sensor Cross-Talk in Student-Built Engineering Education Sorting Cells: A Controlled-Target Evaluation Linking Acoustic Ringing to Misclassification Reliability Bounds

Ultrasonic distance sensors are standard components in student-built sorting cells, yet their susceptibility to acoustic cross-talk between adjacent transducers is rarely quantified in the engineering education literature. The model is evaluated through a replication-based design and power analysis of the before-after-control-impact estimator under a declared variance structure (between-cluster SD = 6.0, residual SD = 4.5, intraclass correlation = 0.64). Power was estimated across 2000 design cells for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The analysis indicates that 54 clusters are required to detect a 5 percentage point effect at 80% power. The derived bounds show that ringing-induced false echoes produce asymmetric misclassification, with false positives dominating at short target distances and false negatives at long distances. The contribution is a design-oriented reliability bound that links transducer spacing, ringing decay time and target distance to the probability of misclassification, providing a quantitative basis for laboratory specification in engineering education.