How Sound Works
The main component of the parasympathetic nervous system is the vagus nerve, which also oversees lots of other functions in the body. The vagal tone (an internal biological process that represents the activity of the vagus nerve ) is correlated with our capacity to regulate stress responses and can be increased in various ways that overlap heavily with how to increase parasympathetic activity.
The vagus nerve is connected to our vocal cords, the muscles at the back of the throat, and importantly, passes through the inner ear. This is why sound is able to activate the parasympathetic nervous system. In fact, the vagus nerve is used to treat tinnitus by stimulating it and playing non-tinnitus audio at the same time. Many studies have shown that listening to relaxing music or music with a slow tempo causes blood pressure to decrease, as well as heart rate and respiration rate. This can be explained by the link between the ears, vagus nerve, and parasympathetic nervous system.
Binaural beats (an auditory illusion where two tones of similar frequencies are played at the same time through headphones) have been proven to increase relaxation as well as both parasympathetic relaxation and increased sympathetic withdrawal. Another study, conducted with elderly patients with cerebrovascular disease and dementia, showed that music therapy enhanced parasympathetic activities in patients. Those same results were replicated in a study concerning post-exercise parasympathetic reactivation, and music was shown to be an effective tool to improve recovery and decrease cardiac stress after exercise.
Heart rate variability has been used to assess the activation of the sympathetic and parasympathetic nervous systems. Therefore, if research showing that sound can increase heart rate variability is to be believed, it follows that sound activates the parasympathetic nervous system as well.
Our stress response is controlled by our autonomic nervous system, which contains both the parasympathetic and sympathetic nervous systems. The parasympathetic helps us recover from stress, but in times of chronic stress or continuous anxiety, the natural progression that would activate the parasympathetic doesn’t kick in, and the nervous system may get stuck with an activated sympathetic nervous system, constantly preparing the body to react to stress, or jump into fight or flight.
In order to activate the parasympathetic nervous system, stress has to be lowered. It would be impossible to remove all external stressors from everyday life, so one very effective way to learn to ignore triggers is meditation, which teaches us to decrease our reactivity to stressors out of our control. Meditation lowers your heartbeat, slows breathing, and lowers blood pressure— all signs of parasympathetic activation. By bringing focused awareness to your body and breathing, meditating activates the parasympathetic nervous system, brings our attention inward, and lowers stress. Meditation can bring the nervous system out of a “stuck” state by almost forcing activation of the parasympathetic nervous system.
In order for sound or music therapy to be fully effective, the focused awareness of meditation should be replicated in the practice of active listening. This can be practiced by focusing fully on the sound (you could sync up your breaths to the rhythm of the music, or assign imagery to different instruments), lying or sitting in a comfortable place, wearing an eye mask or closing your eyes, and using headphones for a fully immersive experience. By combining the effects of meditation and sound, music therapy can produce powerful activation of the parasympathetic nervous system and help regulate autonomic function.