A singer wears earpieces so he can control what he hears. A crowd or band can create background noise, which makes it hard for a singer to hear himself and the accompanying instruments or music track.
Earpieces can be set up to play only the singer's vocals or a mix of vocals and the instruments the singer wants to hear. Because earpieces block ambient noise, singers may have to adjust to what they hear through them. Earpieces, which are technically known as in-ear monitors, are often custom fitted for the singer's ears. They are also offered in different colors. Earpieces reduce noise by 25 to 34 decibels on average.