  We study gravitational waves from a hierarchical three-body system up to
first-order postNewtonian approximation. Under certain conditions, the
existence of a nearby third body can cause periodic exchange between
eccentricity of an inner binary and relative inclination, known as Kozai-Lidov
oscillations. We analyze features of the waveform from the inner binary system
undergoing such oscillations. We find that variation caused due to the tertiary
companion can be observed in the gravitational waveforms and energy spectra,
which should be compared with those from isolated binaries and coplanar
three-body system. The detections from future space interferometers will make
possible the investigation of the gravitational wave spectrum in mHz range and
may fetch signals by sources addressed.
