Any frequency to which a normal human ear responds. The audible range in practice extends from about 20 to 20 000 Hz. Intelligible speech can be obtained in a communication system if a frequency range from about 300 to 3400 Hz is reproduced. Any electronic device, such as an amplifier, choke, or transformer, that operates in this range is known as an audiofrequency device or audio device; similarly any effect, such as distortion, that involves audiofrequencies is termed an audiofrequency effect or audio effect.