beats: the little brown bat is a common bat species in north america. it emits echolocation pulses at a frequency of 40 khz, well above the range of human hearing. to allow observers to "hear" these bats, an electronic bat detector combines the bat’s sound wave at a frequency f 1 with a wave of frequency f 2 from a tunable oscillator. the resulting beat frequency is isolated, amplified, and then played through a speaker. to what frequency f 2 should the oscillator be set in order to produce an audible beat frequency of 3.0 khz? hint: there are two possible oscillator frequencies