We present a numerical study of the interaction of the flame and acoustic waves when a laminar flame propagates in a narrow channel from an open to a closed end. It is shown that the coupling of the flame dynamics and the acoustics can lead to thermo-acoustic instabilities, that can result in large oscillations in the flame speed and pressure inside the duct. Additionally, it is shown that both symmetric and nonsymmetric flames can propagate in these channels and that, because their response to acoustic oscillations is different, their interaction with the acoustic modes of the channel is also different. Therefore, the possibility of symmetry breaking needs to be taken into account in order to correctly predict the onset of acoustic flame instabilities in narrow channels. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.