I think bacteria can make sounds and they can contact each other by vocal messages. What do you think about this idea? I designed a study to examine this hypothesis.
Bacteria cells can produce sound and send vocal messages to each other since they are motile and can exchange genetic materials through conjugation and transduction.
It may senses like: Quorum sensing which is a system of stimulus and response correlated to population density(ref. Wikipedia). I don't know weather it is voice or another connection process?.......