Large units where sheep are reared in Australia are called sheep stations. The term applied to large animal farms inSouth America is estancias. The ranches or sheep stations consist of large areas of natural pasture and also the ranch house and some area devoted to supplementary feed crops.
Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.