In practice , all short - range radio systems “ downshift ” their speeds to compensate for long distances , walls , people and other obstacles 实际上，所有的短距无线电系统为了补偿距离、墙壁、人员和其他阻碍，速度都会下降。
2.
As a result , the low - frequency contents increase as the centroid of signal spectrum experiences a downshift , in case that frequency is independent on quality factor , the offset of the centroid frequency is proportional to the integral of attenuation factor along wavepath , thus can he used to reconstruct the attenuation distribution 假设介质的品质因子与频率无关，地震波主频的偏移量与吸收系数对传播路径的积分成比例，则通过它们之间的关系可以估测介质的吸收系数。
