<Short Communication>Effects of Different Sound on Heart Rate Variability

P(論文)

異なる音源下で起こる生体反応(緊張度)を心拍変動(HRV)によって把握することを試みた。20代の健常者6名を対象とし, 仰臥位の被験者にヘッドフォンから音を聞かせた。音源は(1)浜辺の波音, (2)アラーム音, (3)機械騒音(各70db程度), および(4)無音の4種と設定した。4種の音源から1種ずつ, 被験者に聴取させた。心電図(ECG)のデータから心拍数を読みとったのち, 自己回帰(AR)モデルを仮定してスペクトル解析し, 自律神経の作動バランスを示す指標として低周波成分(LFC : 0.04～0.15Hz)と高周波成分(HFC : 0.15～0.4Hz)の構成比(LFC/HFC)を計算した。平均心拍数を経時的にみると, 全ての音源で減少する傾向にあったが, 機械騒音の場合は実験終了時まで減少率が低かった。LFC/HFCの大きさは, 波音<アラーム音<無音<機械騒音であり, 特に波音は副交感神経系の活性を優位にし, リラクゼーション効果をもたらした。

The analysis of R-R interval of electrocardiogram (ECG) was performed to investigate the physical responses under the condition of four different sounds in 6 normal adult subjects. Recordings were made for 16 min during supine position through a headphone under the condition of four different sounds ; (1) a ripple, (2) alarm (telephone), (3) noise (broken air conditioning), (4) silence. Amount of each spectral component was analyzed by computer system of autoregressive spectral analysis. Low-frequency component (LFC ; 0.04～0.15Hz) and high-frequency component (HFC ; 0.15～0.4Hz) components in the HRV were assessed by the frequency analysis of time-series data obtained from R-R intervals in the ECG ; the LFC/HFC ratio was also calculated. Heart rate of all conditions tended to decrease with the passage of time. However, the decrement of HR in noise condition was less than that in other conditions. LFC/HFC ratio of noise condition was higher than that of other conditions, especially, the ripple. We conclude that the ripple have the effect of sedation and relaxation due to increased parasympathetic activity.