In digitizing operations, the frequency with which samples are taken and converted into digital form. The sampling frequency must be at least twice that of the analog frequency being captured. For example, the sampling rate for hi-fi playback is 44.1KHz, slightly more than double the 20KHz frequency a person can hear. The sampling rate for digitizing voice for a toll-quality conversation is 8,000 times per second, or 8KHz, twice the 4KHz required for the full spectrum of the human voice. The higher the sampling rate, the closer real-world objects are represented in digital form.