We present the results of filtering in the range of periods 5.6–6.7 min of temporal variations in the Doppler frequency shift of the ionosphere-reflected radio signals from the high-frequency vertical ionospheric-sounding radar located near the city of Kharkov during ionospheric plasma modification by high-power periodic (with 6-min period) radio waves of the Sura facility. It is found that switching on and off a series of pulses with 3-min duration and the same pause launched a damped wave process with 6-min period, a delay time of about 30–50 min, and an apparent propagation velocity of about 320–530 m/s. The quasi-periodic variation amplitude of the Doppler frequency shift was 10–40 MHz. The corresponding relative-perturbation amplitude of the electron number density was about 0.1–0.3%. Detected oscillations is evidence that damped infrasound density waves can be generated in the upper atmosphere.