Empirical Study on Low-Frequency Sound Waves of the Maotouqin's Activation of Parasympathetic Nerves: A Heart Rate Variability (HRV) Analysis Approach

This study explores the modulatory influence of the morin khuur's low-frequency acoustic waves on parasympathetic neural activity, aiming to quantify autonomic responses through heart rate variability (HRV) indicators across both time- and frequency-domain analyses, including RMSSD and high-frequency (HF) power metrics. Using a randomized crossover experimental design, 24 healthy adult participants were sequentially exposed to either authentic morin khuur recordings, characterized by a dominant frequency spectrum of 100-220 Hz, or to acoustically matched white noise within a fully shielded, sound-controlled environment. The HRV data revealed a 39.7% increase in high-frequency components (p < 0.01) and a significant reduction in the low-frequency/high-frequency (LF/HF) ratio, indicating a marked enhancement of vagal tone and parasympathetic activity. Beyond the quantitative findings, the results provide physiological evidence that the unique timbral and vibrational qualities of the morin khuur may evoke specific autonomic modulation patterns, distinct from those induced by generic auditory stimuli. These effects may be attributed to the resonant low-frequency components that stimulate somatosensory and visceral feedback mechanisms, leading to a synchronization between auditory processing and autonomic regulation. Building upon prior neurophysiological observations that low-frequency vibrations can activate the nucleus accumbens and related brainstem regions, the present results support the hypothesis of a top-down regulation pathway mediated through the auditory-visceral axis. From a broader perspective, the study extends the theoretical framework of music-based neuromodulation by demonstrating that traditional acoustic instruments are not only cultural artifacts but also potential tools for neuroregulatory interventions. The findings contribute to the growing field of auditory neuroscience by linking specific acoustic features-such as frequency range, resonance, and harmonic structure-to measurable physiological responses. Furthermore, they suggest potential clinical applications in stress reduction, cardiovascular regulation, and biofeedback-assisted relaxation therapies. In conclusion, the low-frequency acoustic spectrum of the morin khuur demonstrates measurable parasympathetic activation, underscoring the biophysiological significance of traditional sound patterns. This work provides a foundation for integrating ethnomusicological acoustics with modern neurotechnology research, offering new insights into how sound-based interventions can modulate the autonomic nervous system and enhance human well-being.