Using the word “signal” presupposes a message sent by someone or something. Anyone using such an unstated premise in a public discussion is uttering junk science.
I disagree vehemently. A signal is just a waveform, that can have many sources. Electrical Engineers (of which I am one) do "signal processing" all the time, and the source can be blasted anything.
A "communication" would be a different matter.
https://en.oxforddictionaries.com/definition/signal
2. An electrical impulse or radio wave transmitted or received.
I use the word every day at work. It does not necessarily mean anything communicated. I trace a ‘signal’ through a circuit. I follow a ‘signal’ thru a system. .............