noun which may take the genitive case particle 'no', prefix
ultra-low; very low; hyper-; infra-
Prefix-like element used in technical and descriptive compounds to mean extremely low in height, temperature, frequency, etc. Not a standalone word; always attaches to another noun.
超低温で保存する必要がある。
It needs to be stored at ultra-low temperatures.
超低周波の音は人間には聞こえない。
Ultra-low frequency sounds are inaudible to humans.