Longhini C, Toselli T, Masotti G, Bellotti E, Portaluppi F, Ansani L, Arslan E
Jpn Heart J. 1982 Sep;23(5):711-6. doi: 10.1536/ihj.23.711.
The first heart sound was studied in 20 normal subjects. The phonocardiogram (PCG) was recorded from apical and mid-precordial areas using microphone with a flat response curve from 0.2 to 8,000 Hz. It was stored, together with a simultaneous electrocardiogram, on an FM analog tape recorder (linear frequency response from 0 to 4,000 Hz), fitted with a filter with weighting curve B according to the American National Standard Institute. A linear (SPL) recording was also made. The signal was fed through a digital converter into a minicomputer and the frequency distribution of the first heart sound was analyzed using Fast Fourier Transform. These data were stored and the average spectra were calculated for both B and SPL. The SPL spectra from both apex and mid-precordium showed a maximum intensity of about 80 dB between 12-20 Hz, decreasing progressively to a constant level of 35 dB between 110-120 Hz. The spectra obtained from both areas using filter B showed a maximum intensity of 40-50 dB between 20-60 thereafter. It is important to emphasize that the dB values in B and SPL are absolute, since they refer to a standard reference weighting. It appears that the SPL recording is more valuable in that it allows the study of all components of the PCG signal. The spectra obtained in this study will be used as a standard for future research in various pathological conditions.
对20名正常受试者的第一心音进行了研究。使用响应曲线在0.2至8000赫兹范围内呈平坦状的麦克风，从心尖区和心前区中部记录心音图（PCG）。它与同步心电图一起存储在一台调频模拟磁带录音机上（线性频率响应范围为0至4000赫兹），该录音机配有根据美国国家标准学会的加权曲线B的滤波器。还进行了线性（声压级）记录。信号通过数字转换器输入到一台小型计算机中，并使用快速傅里叶变换分析第一心音的频率分布。这些数据被存储起来，并计算出B加权和声压级的平均频谱。来自心尖区和心前区中部的声压级频谱在12至20赫兹之间显示出约80分贝的最大强度，在110至120赫兹之间逐渐下降至35分贝的恒定水平。使用滤波器B从这两个区域获得的频谱此后在20至60赫兹之间显示出40至50分贝的最大强度。必须强调的是，B加权和声压级中的分贝值是绝对的，因为它们参考了标准参考加权。看来声压级记录更有价值，因为它允许对心音图信号的所有成分进行研究。本研究中获得的频谱将用作未来各种病理状况研究的标准。
