Infrasonic arrays are a powerful tool for volcanic monitoring and hazard assessment. Explosions were recorded at Stromboli using a small aperture array of 4 infrasonic stations, allowing precise vent location. The acoustic signals were delayed-and-summed, revealing the existence of two main groups of infrasonic waves. The NE crater produces short (<3 s) high amplitude (20--80 Pa) pressure waves while the SW crater produces small acoustic pressure (10--30 Pa) with long (5--15 s) coda. The two groups reflect different in explosive styles and similar spectral content, centered on 5--6 Hz. When stacked together, acoustic waveforms for each crater reveal the same pressure pulse, which indicates a common source process. We infer that the acoustic onset at both craters is generated by the burst of a large gas bubble while the acoustic coda is controlled by a sustained pressure release.