During a seismo-acoustic experiment we recorded volcanic tremor around the summit craters of Mt. Etna volcano. Tremor shows amplitude modulation, which disappear ≈900 m from the crater area. The infrasonic wavefield is coherent even at distances of ≈750 m. Time delay between infrasonic transient is stable around 1.3 s and is consistent with the position of the source in the Voragine crater. Amplitude modulation of tremor is well correlated (0.72) with infrasound amplitude with a time lag of 0.37 s, coherent with a shallow position of the source. Amplitude of volcanic tremor decays over increasing distances according to geometrical spreading of body waves. Tremor wavefield shows a linear polarization following the same time occurrence as the infrasonic pulses. Polarization azimuth indicates that wavefield rectilinearity is mostly due to P-waves. We infer that most of the volcanic tremor we recorded at Mt. Etna is generated by superimposition of small impulsive sources acting at 1--2 s rate caused by pressure instability during magma degassing. ¿ 2001 American Geophysical Union