Abstract Frothers are surfactants used in flotation to aid generation of small bubbles, an effect attributed to coalescence prevention. Studying coalescence at the moment of bubble creation is a challenge because events occur over a time frame of milliseconds. This communication introduces a novel acoustic technique to study coalescence as bubbles are generated at a capillary. The sound signal was linked to bubble formation and coalescence events using high-speed cinematography. The technique has the resolution to detect events that occur within 1–2 ms. The results show that for common flotation frothers and n-alcohols (C 4–C 8) coalescence prevention is not simply related to surface activity. A total stress model is used to give a qualitative explanation to the action observed. Results for salt (sodium chloride) are included for comparison.