Frequency

The rate of vibration of an electrical or mechanical oscillation. Measured by the number of complete cycles executed in 1 second. In audio terminology, frequency range is considered to be from 20 cycles per second, or 20 Hertz (Hz), up to 20,000 cycles per second, or 20 kilohertz.

The number of oscillations of a signal over a given period of time (usually one second). For example it defines subcarrier frequencies in analogue systems, or clock rate frequencies in digital systems. Here are some commonly found frequencies in TV:

• PAL subcarrier: 4.43 MHz
• NTSC subcarrier: 3.58 MHz
• ITU-R 601 clock rate: 27 MHz
• ITU-R 601 luminance sampling rate: 13.5 MHz
• ITU-R 601 chrominance sampling rate: 6.75 MHz
• HDTV Y sampling rates: 72 MHz (1250/50), 74.25 MHz (1125/60)

Frequency Response

The variation of response with respect to signal frequency. Usually, the frequency response of a tape is given in dB relative to that of a reference tape measured under the same conditions.

Frequency Response Curve

The curve relating the variation in output with frequency of a piece of equipment or magnetic tape when the input is kept constant.