In　this　work,　the　pressure　wave　propagation　in　the　vertical　and　horizontal　directions　has　been　studied　using　a　self-designed　clapboard-type　internally　circulating　fluidized　bed.　The　effects　of　flow　regimes　and　solid　mixture　on　the　pressure　wave　propagation　characteristics　were　analyzed　in　terms　of　time-averaged　pressure,　standard　deviation,　power　spectral　density,　dominant　frequency,　propagation　time　delay,　and　attenuation.　The　superficial　velocity　ratio　had　a　remarkable　effect　on　the　pressure　wave　propagation　time　delay　in　the　vertical　direction　but　had　less　influence　on　the　pressure　wave　propagation　in　the　horizontal　direction.　The　particle　circulation　provided　an　extra　resistance　force　to　the　horizontal　pressure　wave　propagation　and　resulted　in　an　increase　in　the　pressure　wave　decay　factor　in　the　horizontal　direction.　The　addition　of　glass　beads　and　salt　greatly　increased　the　time　delay　and　decay　factor　both　in　vertical　and　horizontal　directions.　The　addition　of　15%　corn　powder　(Geldart-C　group)　reduced　the　propagation　time　delay　but　increased　the　decay　factor.　©　2020　The　Society　of　Powder　Technology　Japan