Children and babies have even higher fundamental frequencies. Infants show a range of 250 to 650 Hz, and in some cases go over 1000 Hz. A 10-year-old boy or girl might have a fundamental frequency around 400 Hz. When we speak, it is natural for our fundamental frequency to vary within a range of frequencies. This is heard as the intonation pattern or melody of natural speech. When we sing a song, we are controlling the fundamental frequency of our voice according to the melody of that song. Since a person's voice typically varies over a range of fundamental frequencies, it is more accurate to speak of a person having a range of fundamental frequencies, rather than one specific fundamental frequency, Nevertheless, a person's relaxed voice usually can be characterized by a "natural" fundamental frequency that is comfortable for that person.