Low-frequency Raman spectroscopy measurements are performed at atmospheric pressure on low (LDA)- and high (HDA)-density amorphous ices. The HDA is annealed at 15 kbar, up to 160 K. It is found that the low-frequency Raman profile of the HDA is similar to that of liquid water, but is different from that of crystalline ices. This result indicates that the structure of the hydrogen-bonded networks in HDA is liquid-like.