I think the first sound was when another spirit tried to come through, but it didn't work. I think the spirits were not sure if it worked and one of them say 'try it' which came through on the speakers. I think the voice actually said 'try it' and not 'child'.

These transmitters could be generating thousands of watts of RF power. Although it sounds weird, it may be possible the spirits use these radio transmissions to feed on the energy. Its possible the Morse code is from a local ham radio person transmitting and picked up by the instruments. This is not the first time I heard Morse code on paranormal shows. The first one was three dots (.) which is 'S' and then second was a dot and dash (.-) which is 'A' and last one was two dashes (-) which is 'M' (or it could be a single long dash which is a 'T'). The tones actually sounds like Morse code. They should just combine the two instruments because it would be interesting to see and hear when the Trifield meter picks something up.

Both the Trifield meter and the pod captured the same phenomenon at exact same time. When the voice saying 'child' came through, you also hear the three tones before the voice came through and then you see two more after it was done. The Trifield also recorded the same change. One at max energy at around 10, and then the second one at 6 before it drops down. When the first sound came through, it was at least two tones. The polterpod caught that as a beep sound and you can see the Trifield meter respond with three small pulses.

Right before the first sound, there were three very low level tones. Go back to the episode and watch the Trifield meter carefully.

Ghost adventures s07e09 tor house