In the present study, the Perceptual Assimilation Model (PAM) was tested on its applicability in child L2 lexical tone acquisition. The possible effect of L1 (Cantonese) lexical tones on L2 (Mandarin) lexical tone learning was explored. Accuracy rate and error patterns were examined with an AX discrimination task and a forced-choice identification task. Forty-nine native Cantonese-speaking students aged 8 years participated in the study. Results revealed that these children exhibited nearly perfect performance in the discrimination of Mandarin tones. However, significant tone differences were detected in the identification task. Tone 4 (T4) was identified with the lowest accuracy, and T1 with the highest. Error analysis revealed that Mandarin T2-T3 was the most confusing pair, followed by the T1-T4 pair. The inherent phonetic similarity between lexical tones in a language and the tone similarities across languages may also have contributed to perception difficulties, which could help to refine and supplement the PAM in the tonal/suprasegmental domain.

The T-POD (Timing POrpoise Detector) is a self-contained acoustic data logger used for detecting and monitoring the presence of echolocation clicks of small cetaceans. It has become a standard tool in environmental impact assessments and monitoring programmes. Yet, little is known about the variability in sensitivity and detection range of T-PODs. In this study the field performance of ten v3 T-PODs was compared to detection thresholds measured in a tank. The T-POD thresholds ranged from 123 to 132 dB re 1μPa (pp). The detection thresholds of the ten individual T-PODs were different and the differences increased over time. The more sensitive a T-POD was in the laboratory (i.e. the lower the threshold) the more clicks were recorded by it in the field. Threshold correlated differently to the five analysed T-POD parameters (encounters, encounter duration, waiting time, porpoise positive minutes, clicks per porpoise positive minute). This study demonstrates that individual threshold calibrations of T-PODs are necessary to obtain comparable results when monitoring odontocetes with this tool. Regression equations for relationships between T-POD detection thresholds and study parameters obtained during field trials may allow comparisons of T-PODs with different detection thresholds.