Conversing is one of the most human things we do and we do it a great deal. Our brains have evolved with special channels in and out for language. Most people know of the posterior Wernicke’s area important to language comprehension and of the anterior Broca’s area important to language production. These are basic to conversation of course.
The speech signal is an unbroken stream of sound produced by air blowing through the vocal folds and then modulated by the speech tract (pharynx, nasal cavities, tongue, teeth, lips) to mark phonemes (vowels and consonants). The auditory system processes this signal and somehow recovers the linguistic units to find words, sentences, etc. Our brains do this rapidly and all at once, which makes it possible to interrupt someone to say what we want rather than listen to them. More on manners later. Here is a graph of the speech signal for a sentence that took 1.5 seconds to utter (must have been a slow drawl at that).
No breaks are between words, the stress or accent on different syllables is indicated by the amplitude of the graph, and the phonemes are there somewhere. That is not the whole story, however, because while the left side of the brain is encoding/decoding the syntactic units, the right side is doing the same for the paralinguistic aspects of the signal, the intonation patterns carrying the sentence modality (statement, question, exclamation, etc.), the emotional cues therein, even the basics of the speaker’s identity, sex, age, geographic origin, etc. This is done all the while as the right side also monitors the non-verbal cues for the listener’s interest and attitude along with the rest of the immediate concrete situation. Again the left side’s language may be about information immediately available in the current situation but more probably is about information displaced in time and space, real or unreal.
The term ‘voice’ is used in many ways, a speaker’s basic necessity, a singer’s instrument, a poet’s distinctive mode of expression, etc. Biologically voice is the special sound to which our brains are attuned; a good part of our brains is dedicated to receiving and producing this figure so distinctive from the ground of ambient noises. And not just humans. The latest issue of Science News reports a study in which dogs were trained to lie very, very still in an MRI while sounds were played. The results indicated that dogs also pay special attention to voice though not to the same degree as humans, which only makes sense given how well they engage with us and us with them in a special sort of conversation in which they are the better listeners and speak with their eyes, tongue and tail.
Coming soon: conversation and music