The audio will not come out unless you also have the microphone connected. It took me days and 3 earbuds to figure out. What you can do is build an electret microphone circuit powred by 3.3 volts an 1k ohm resistor.
For where the signals come out you will have to plug in a cheap earbud with bluetooth and with a scope pind the signals. Geraly with the linkit TRRS audio socket pointing to the right the third pin on the edge of the board is the audio output. The microphone is above that one and the third pin back.
you must have the plug inserted for it to work, i might be wrong . you will have to test for output if plug not in socket. i was experimenting but nothing would work then. Hope it helps some.
ljay0778