Ultrasound: mouse and rat repeller

I love the definition of ultrasound: any frequency above the highest that a human can hear. The highest we can hear is 20000Hz. This unit sweeps from 30000 up to 60000Hz. This is important because cats and dogs can hear up to 27000Hz so they are not distressed by the device. The garage is an ideal location for it because the hard wall surfaces reflect the sound round the space so one unit can cover the entire room.