OK I have a local .wav sample audio file working and playing on my Google Home speaker in the Kitchen via Node-Red.
This can be either triggered by a Scene in Vera with some LUA code or can be triggered by a virtual motion sensor I just created on my Vera Plus.

I’ve configured it so the virtual motion sensor must be Armed and Tripped e.g. ArmedTripped=1 for Node-Red to then play the .wav file.
Further more detailed information can be read in the text items in the Node-Red Flow.
Here is the Node-Red code you can import:
[{"id":"a300d823.d91888","type":"tab","label":"Audio Alerts","disabled":false,"info":""},{"id":"7c792e59.49c9b","type":"comment","z":"a300d823.d91888","name":"Dog Alert","info":"","x":80,"y":20,"wires":[]},{"id":"5245d4ba.777cfc","type":"http in","z":"a300d823.d91888","name":"","url":"/dog1","method":"get","upload":false,"swaggerDoc":"","x":80,"y":140,"wires":[["9a183a60.09fb28"]]},{"id":"e78fbd8e.3d3b9","type":"http response","z":"a300d823.d91888","name":"","statusCode":"","headers":{"content-type":"audio/mpeg"},"x":390,"y":140,"wires":[]},{"id":"9a183a60.09fb28","type":"file in","z":"a300d823.d91888","name":"Dog1","filename":"/home/pi/.node-red/naughty-dog.wav","format":"","chunk":false,"sendError":false,"x":230,"y":140,"wires":[["e78fbd8e.3d3b9"]]},{"id":"f6382b78.927ec8","type":"mios-in","z":"a300d823.d91888","name":"Noise Alert (Virtual Motion Sensor)","server":"db098590.052cd8","item":"Kitchen:Noise Alert:ArmedTripped","exact":false,"x":160,"y":320,"wires":[["38aa21bd.36581e"]]},{"id":"38aa21bd.36581e","type":"switch","z":"a300d823.d91888","name":"Noise Detected","property":"payload","propertyType":"msg","rules":[{"t":"eq","v":"1","vt":"str"}],"checkall":"true","repair":false,"outputs":1,"x":440,"y":320,"wires":[["5939e7a.7204218"]]},{"id":"46c31311.5c3a0c","type":"cast-to-client","z":"a300d823.d91888","name":"Kitchen-Speaker","url":"http://192.168.0.4:1880/dog1","contentType":"","message":"","language":"En-gb","ip":"192.168.0.19","port":"8009","volume":"","x":370,"y":440,"wires":[[]],"icon":"node-red-contrib-cast/google-home1.svg"},{"id":"d5547bb5.4c16b8","type":"http in","z":"a300d823.d91888","name":"http request from scene","url":"/audioTrigger1","method":"get","upload":false,"swaggerDoc":"","x":120,"y":440,"wires":[["46c31311.5c3a0c"]]},{"id":"69e3ad12.3c8d34","type":"comment","z":"a300d823.d91888","name":"Triggered from a Vera Scene - (Double Click for more info)","info":"Run this LUA code from your Vera Scene - Change to your Node-Red IP \nluup.inet.wget(\"http://192.168.0.4:1880/audioTrigger1\")\n\n/audioTrigger1 is specified in the HTTP IN Node in the URL field and can be changed if you wish.","x":230,"y":380,"wires":[]},{"id":"5939e7a.7204218","type":"cast-to-client","z":"a300d823.d91888","name":"Kitchen-Speaker","url":"http://192.168.0.4:1880/dog1","contentType":"","message":"","language":"En-gb","ip":"192.168.0.19","port":"8009","volume":"","x":650,"y":320,"wires":[[]],"icon":"node-red-contrib-cast/google-home1.svg"},{"id":"4e68f8d8.a6f268","type":"comment","z":"a300d823.d91888","name":"Audio File served up by HTTP in Node-Red - (Double Click for more info)","info":"I uploaded my .wav file on to my Raspberry Pi were Node-Red is running in to the /home/pi/.node-red/ directory.\n\nThe full path to this file and its name is:\n\n/home/pi/.node-red/naughty-dog.wav\n\nThe GET URL is /dog1 \n\ne.g. entering http://192.168.0.4:1880/dog1 in to a web browser you can test if the audio file is being served up by Node-Red HTTP ? \n\nChange the IP address to that of your own Node-Red","x":280,"y":80,"wires":[]},{"id":"817c54e1.981ec8","type":"comment","z":"a300d823.d91888","name":"Triggered by Vera device - Virtual Motion Sensor - (Double Click for more info)","info":"In Vera my virtual motion sensor is named \"Noise Alert\" and is in the \"Kitchen\" room. \n\nNOTE - Also the virtual motion sensor must be Armed.\n\nTherefore the MIOS device item I am monitoring for in Node-Red is:\n\nKitchen:Noise Alert:ArmedTripped\n\nYou can test and manually trip your virtual motion sensor by entering this in to a web browser:\n\nhttp://VERA-IP/port_3480/data_request?id=lu_variableset&DeviceNum=X&serviceId=urn:micasaverde-com:serviceId:SecuritySensor1&Variable=Tripped&Value=1\n\nEnter your Vera's IP address and the device number of your virtual motion sensor in the DeviceNum=X change X for the device number etc.\n\nYou can untrip it by setting it to ZERO instead\n\nTripped&Value=0","x":290,"y":200,"wires":[]},{"id":"6b14f43b.aefe3c","type":"comment","z":"a300d823.d91888","name":"Google Home / Cast (Double Click for more info)","info":"In the Cast devices specify the static LAN IP address of your Google Home speaker in the IP field. \n\nSpecify the port number of: \n\n8009\n\nIn the MediaURL field specify the GET of the HTTP hosted audio file. \n\nMine is:\n\nhttp://192.168.0.4:1880/dog1\n\nChange the IP address to that of your own Node-Red.\n\nIn the Language field specify either:\n\nEn-gb OR En-us OR some other language. \n\n\n\n\n\n","x":660,"y":440,"wires":[]},{"id":"1cc52c04.80b9c4","type":"comment","z":"a300d823.d91888","name":"Google Home / Cast (Double Click for more info)","info":"In the Cast devices specify the static LAN IP address of your Google Home speaker in the IP field. \n\nSpecify the port number of: \n\n8009\n\nIn the MediaURL field specify the GET of the HTTP hosted audio file. \n\nMine is:\n\nhttp://192.168.0.4:1880/dog1\n\nChange the IP address to that of your own Node-Red.\n\nIn the Language field specify either:\n\nEn-gb OR En-us OR some other language. \n\n\n\n\n\n","x":640,"y":260,"wires":[]},{"id":"db098590.052cd8","type":"mios-server","z":"","name":"Vera-Plus","host":"192.168.0.12","port":"3480"}]
Attached is my naughty-dog.wav sample file also. naughty-dog.zip (1.7 MB)
I am using the node-red-contrib-cast and the node-red-contrib-mios nodes in my palette.
You will need to install these in to Node-Red first and establish the connection in the MIOS node to your Vera’s LAN IP address and its API port number - 3480
And also connect the Cast nodes to your Google Home speaker via its IP address and its port number - 8009
It would be nice to be able to randomly play different local .wav or .mp3 files, haven’t figured that out as yet.
And now I need some way of detecting the dog barking to then trigger the virtual motion sensor in Vera to then have the .wav file play out on the Google Home speaker etc.
Suggestions ?