This tool captures your microphone input and displays a real-time frequency spectrum. The vagal tone range — roughly 500 to 2000Hz — is highlighted. This is the frequency band where human voice prosody lives.
The vagus nerve (cranial nerve X) responds to specific sound frequencies. It shares circuitry with the facial nerve that controls the stapedius muscle in the middle ear — a tiny muscle that tunes your hearing toward or away from human speech.
When you feel safe, the stapedius contracts and filters for the prosody band. You hear the melody of speech — the rise and fall that carries emotional information. When you feel threatened, it relaxes, and low-frequency rumble floods in.
Voice prosody carries emotional information through these frequencies. A soothing voice activates the social engagement system. The vagus nerve links the ear to the heart, the gut, the face. What you hear changes how your body feels — before you consciously process the words.
Press start and speak, hum, or play music near the microphone. Watch the vagal engagement indicator. Soothing, melodic speech will light up the prosody band. Low rumbles and sharp noises will shift energy away from it.