The birds sing at night, but sometimes there are strong winds and if it rains, they are quiet. These recordings are discarded because nobody is interested in the silence of the birds. The recordings are so long, months, even years, that there is no chance he can listen to all of it.

Sitting in his office, on a chair that rotates, Karl looks into the screen of his computer. He could use cheap labor or hire students as interns, but he does not like the idea of outsourcing the listening. Instead, highly reliable pattern recognition algorithms are used to detect the voices.