Humming Breathing as a Device-Free Method for Inducing Resonance Frequency: A Preliminary Investigation into Autonomic Regulatory Mechanisms

Objective: This study aimed to determine whether the effects of humming breathing (Bhramari Pranayama) on the autonomic nervous system were caused by vibratory sounds or specific respiratory patterns. Methods : Eleven healthy adults participated in four randomized sessions (rest, deep breathing, humming breathing, and calm humming breathing) over five consecutive days. Heart rate variability and respiratory measures were analyzed, along with visual analog scale responses for stress, anxiety, confidence, and relaxation. Results : Humming and calm humming breathing resulted in lower respiration rates and less variability than those of rest and deep breathing, with a target resonance frequency of 0.1 Hz. All breathing conditions showed higher root mean square of successive differences, standard deviation of normal-to-normal intervals, total power, and low-frequency power values, along with lower high-frequency power peaks, compared with those of rest. Humming breathing exhibited higher standard deviation of normal-to-normal intervals, total power, and low-frequency power values than those of deep breathing. Visual analog scale analysis revealed no significant differences across the breathing conditions. No significant differences were observed between humming and calm humming breathing for any of the measures. Conclusion : The effects of humming breathing appear to be associated with the 0.1 Hz resonance frequency induced by extended exhalation with an “mm” sound rather than the vibratory sound itself. Humming breathing, which does not require a biofeedback device, is a practical alternative to cyclical breathing.