Then you need a small speaker with a 3.5mm connector. If I were you I’d completely ditch the phone, get a small enough speaker with 3.5mm adaptor, connect it to an MP3 shield and hide these all behind the painting. MP3 shields usually have their own SD Card adaptor as well which makes sense for you because you somehow need to store your MP3 formatted voice files.
Actually you don’t need 3.5mm connector, I just checked SparkFun’s MP3 shield and it has places that you can connect a right and a left speaker with ground. You just need to find a flat enough speaker for this project. Here is the link, and I’m sure you can find a copy of this for cheaper:
SparkFun MP3 Player Shield - DEV-12660 - SparkFun Electronics
This one might be even better for your application, check this one out as well please:
I think the solution with MP3 shield is easier because the Android program is difficult for me. (I have 0 knowledge on android programming, so i prefer avoid that ^^).
Is there a software that allows me to simulate this system ?? I would like to avoid buying the components if it does not work.
That gives me much clearer concept of your project. You should have said that in your Original Post.
If you are using the phone to play music then it does seem to me both practical and sensible to use an Arduino to send it a Bluetooth message when the PIR detects movement. (However I am not contradicting those who have suggested the alternative of an MP3 shield.)
You will need to create the Android program (I’m assuming you have an Android phone) to receive and interpret the message from the Arduino and creating an Android program is outside the scope of this Forum.
How to receive and interpret a message sent in bluetooth?
All I can do is receive info on an android terminal via an application.
if you have tutorials, … I take ^^