Using　symmetry　reduction　concept,　the　band　gap　properties　of　a　two-dimensional　hybrid　triangular　lattice　phononic　crystal　were　investigated　both　theoretically　and　experimentally.　The　band　structure　was　calculated　with　the　plane　wave　expansion　(PWE)　method.　The　results　revealed　that　the　band　degeneracy　at　high　symmetry　point　in　the　first　Brillouin　zone　was　lifted　due　to　reducing　symmetry,　and　hence　a　new　low-frequency　absolute　band　gap　between　the　first　and　the　second　bands　appeared.　The　measured　transmission　spectra　were　found　to　be　in　good　agreement　with　the　numerical　results.　(C)　2010　Elsevier　Ltd.　All　rights　reserved.