We describe time-series observations of small-scale Can emission features located outside the network in the quiet chromosphere. Simultaneous spectra in K and λ8542 show unambiguously that the evolutionary behaviour of the K-line profile is due to an outwardly propagating velocity pulse. Assuming that this pulse is a progressive acoustic wave, as suggested by the inferred flow parameters, we show that the wave loses mechanical energy in traversing the chromosphere. This implies that the bright Can features (K grains) are the manifestation of local heating in the chromosphere, possibly by shock waves.