Our　group　has　designed　three-dimensional　(3D)　continuously　graded　phononic　crystals　(PCs)　and　experimentally　studied　the　sound　absorption　characteristics　of　the　continuously　graded　PCs.　However,　no　attention　has　been　paid　on　air　background-based　gradient　phononic　crystals　(GPCs),　for　which　the　inclusions　and　the　matrixes　are　photosensitive　resin　and　air　respectively.　In　this　paper,　the　acoustic　characteristics　of　air　background-based　GPCs　are　investigated　and　discussed.　The　uniform　phononic　crystals　(UPCs)　are　designed　for　reference.　The　experimental　results　show　that,　compared　with　UPCs,　the　GPCs　have　better　sound　absorption　performance　when　the　frequency　is　from　2750　Hz　to　5500　Hz.　And　there　is　good　agreement　between　the　experimental　results　and　semi-analytical　results　of　sound　absorption　coefficients　of　the　two　kinds　of　PCs.　The　relationship　between　sound　absorption　coefficient　and　specific　acoustic　impedance　is　discussed　as　well.　The　specific　acoustic　resistances　and　specific　acoustic　reactances　of　the　GPC-0.6-30　mm　are　more　close　to　the　300-900　Pa•s/m　and　0　Pa•s/m　respectively,　which　result　in　better　sound　absorption　performance.　The　GPCs　are　expected　to　have　potential　application　in　the　noise　control.　Copyright　©　(2018)　by　International　Institute　of　Acoustics　&　Vibration.　All　rights　reserved.