the ultrasonic vocalizations emitted by rats and mice have been categorized. there are three classifications: 22-khz vocalizations, 40-khz vocalizations, and 50-khz vocalizations. the 40-khz calls are short in duration, lasting anywhere from 80-150 milliseconds, while the 50-khz calls tend to be even shorter, lasting anywhere from 20-100 milliseconds. in contrast, the 22-khz calls are longer in duration, ranging from 300-3000 milliseconds. adults emit the 22-khz and 50-khz vocalizations, while pups emit 40-khz vocalizations. ultrasonic vocalizations are not precisely 22-, 40- and 50-khz. 22-khz calls can range from 18-32-khz, 40-khz calls range from 40-70-khz, and 50-khz calls range from 35-72-khz.