Measuring the mass and distance of a gravitational wave (GW) source is a fundamental problem in GW astronomy. The issue is becoming even more pressing since LIGO and Virgo have detected massive black holes that in the past were thought to be rare, if not entirely impossible. The waveform templates used in the detection are developed under the assumption that the sources are residing in a vacuum, but astrophysical models predict that the sources could reside in the close vicinity of supermassive black holes (SMBHs). In this talk, I will show how the nearby SMBH could distort the GW signals and change their apparent physical parameters by strong gravitational lensing, as well as by inducing significant Doppler shift. These effects, if not appropriately accounted for, may alter our understanding of the formation and evolution of the LIGO/Virgo/Kagra black holes, as well as mislead our measurement of the cosmic expansion history of the universe.