Abstract: A portable therapeutic instrument includes a microphone to be secured to a patient's throat for monitoring voice level or to a patient's nose for monitoring nasal sounds. An input amplifier includes an automatic gain circuit which essentially flattens the gain curve. An adjustable level detector includes a solid state level detector to generate a square wave signal connected to a logic switching circuit for turning a tone oscillator or other stimulus unit wholly on or off. A second similar channel connected to the input amplifier detects total voiced speech. A switch means connects the oscillator to only the first channel to detect speech above a selected level or to both channels to detect speech only below a selected level. The several channels include time delay circuits permitting normal speech attack and decay. The microphone may also be connected to the patient's nose to monitor nasal sounds.