This study expands on the practical application of the critical role of auditory processing in the rate of naturalistic L2 speech acquisition. In Study 1, the prosodic production of English by 46 Chinese college students was tracked over a five-month study abroad program in the UK. Learners with extensive L2 input opportunities demonstrated improvements in prosodic accuracy; however, those with pitch acuity below a certain threshold showed regression, potentially reinforcing L1 interference. To determine what percentage of participants fell below the auditory processing threshold determined in Study 1, Study 2 administered pitch processing tests to 400 Chinese college students learning English, all with normal hearing, and developed a provisional corpus to assess pitch acuity variation within this cohort. The comparison of findings from Studies 1 and 2 suggests that insufficient auditory precision hampers naturalistic L2 learning. Approximately the bottom 1.5 quartiles of the population (35%) may fall below this threshold. These learners could benefit from remedial strategies (e.g., explicit phonetic instruction, auditory training) to fully capitalize on their naturalistic L2 learning opportunities.