Animals and humans have different hearing ranges, meaning that we hear different sound wave ranges from other creatures.
Every species has a hearing range, and often some of those ranges are shared. These frequency ranges are measured in Hertz (Hz) and Kilohertz (kHz). Humans can detect sound waves from 20 Hz up to 20,000 Hz. As a general rule, smaller mammals detect higher ranges and larger animals lower ranges. An elephant has a range of 16 Hz to 12,000 Hz. Many noises they make are undetectable to the human ear. A cat's range is from 45 Hz to 64,000 Hz — they will hear things at the higher range that humans and elephants will miss. Dogs often hear high-pitched noises we are entirely oblivious to because their range extends up to 45,000 Hz.