The red & the white wires go to the output device.

Note whether one or two pairs of black and white wires are attached.

There was a white wire about three feet long coming out of one end.

You should find either one black and one white wire or else two of each.

This will leave one each of short black and white wires unattached.

Blue and white wires peeked out from under the bushes.

Then touch the probes to the white wires and the box.

Sound: The pair of white wires carries the signal to the speaker.

Usually the white wire is negative on these, although that isn't really a hard and fast rule either.