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The Standard Terminal Automation Replacement System (STARS) was introduced to eliminate unnecessary Air Traffic Control (ATC) alarms and reduce air traffic controller confusion about alarms. The six STARS alarms are tonal melodies. Because of this, they are susceptible to simultaneous masking: where a tone cannot be heard in the presence of other sounds due to limitations of the human sensory system. This work used a proof-based computational method to analyze the STARS alarms to determine if any masking is possible. Our results found three instances where alarms could be partially masked (have part of their signal made inaudible) by other simultaneous alarms. More importantly, one alarm could be totally masked (rendered completely inaudible) in the presence of three others. In this paper we describe this analysis. We also suggest standardizing the volumes of alarms to prevent the potential for total masking.