This is done by controlling how the search is performed with an integer ranging from 1 to 10 in a way similar to the -1 to -9 options to gzip compression utilities. For normal use, the noise level at complexity 1 is between 1 and 2 dB higher than at complexity 10, but the CPU requirements for complexity 10 is about five times higher than for complexity 1. In practice, the best trade-off is between complexity 2 and 4,[13] though higher settings are often useful when encoding non-speech sounds like DTMF tones, or if encoding is not in real-time.