Insect hearing organs vary in their ability to discriminate among sounds. Insects that need hearing to do one thing well, such as warning of an approaching bat, can have an auditory system that only responds to sounds made by bats. Some sphingid moths have a single auditory neuron in each tympanum that triggers evasive flight activity.
Using sound to identify, locate and find mates requires more sophisticated auditory processing systems. The auditory organs of cicadas can contain a couple thousand sensory neurons. The Johnston’s organs of male mosquitoes that are capable of sophisticated tone matching can contain 15,000 neurons. In comparison, the human ear contains around 16,000 sensory hair cells in the cochlea.
Martin C. Gopfert and R. Matthias Hennig. Hearing in Insects. Annu. Rev. Entomol. 2016. 61:257–76.