I need black bars on the left and right sides Corona sdk for Android

Question

How a can make game with not all screen in horizontal orientation? I need black bars on the left and right sides like on the picture.

my config.lua

application =

{ content = { width = 320, height = 480, scale = "letterbox", fps = 60,

    --[[
    imageSuffix =
    {
            ["@2x"] = 2,
            ["@4x"] = 4,
    },
    --]]
},

}

build.settings

orientation =
{
    -- Supported values for orientation:
    -- portrait, portraitUpsideDown, landscapeLeft, landscapeRight
    default = "landscapeRight",
    supported = { "landscapeLeft", "landscapeRight", },
}