I updated and upgraded my Halloween skeleton riding a bicycle (https://youtu.be/lKh1Qiu-vBM) display this year.
I made a video (using my tablet) of the bicycle horn (last year). This year I mixed the horn video with a downloaded (YouTube) video of a barking growling dog. Then I converter the video to a wav file. The wav file is played through my BVC software (other software can do the same) when the X10 setup/BVC "hears" the signal from an eagle-eye motion sensor hidden in the display.
See the video (https://youtu.be/lKh1Qiu-vBM)
I know the X10 Halloween displays are kinda old-fashioned.... but I am kinda an old man.