Short high-pitched sound (4)
(Other definitions for beep that I've seen before include "Sound of pager" , "Toot" , "Short high-pitched sound from an electronic device" , "Honk" , "Sound of a horn" .)
(Other definitions for squeak that I've seen before include "Pip's partner -- quakes (anag)" , "(Succeed by) a narrow margin" , "Sound of a mouse" , "Short high-pitched cry as of mouse" , "Short, high-pitched noise" .)