Aliasingilmiön

Aliasingilmiön, often referred to as aliasing, is a phenomenon that occurs when a continuous signal is sampled at a rate that is too low. When a signal is sampled, it is converted from a continuous waveform into a discrete sequence of data points. If the sampling rate is less than twice the highest frequency component present in the signal, then the higher frequencies will be misrepresented as lower frequencies in the sampled data. This can lead to distortions and misinterpretations of the original signal's characteristics.

The Nyquist-Shannon sampling theorem states that to accurately reconstruct a continuous-time signal from its samples, the sampling frequency must be at least twice the highest frequency present in the signal. This minimum sampling frequency is known as the Nyquist rate. If this condition is not met, aliasing will occur. The aliased frequency will appear as a new, lower frequency component that was not present in the original signal.

Aliasing can be a significant problem in various fields, including digital signal processing, image processing, and audio recording. For example, in digital audio, if a signal is sampled below the Nyquist rate, high-frequency sounds can be incorrectly reproduced as lower-frequency sounds, leading to an unnatural or distorted audio experience. In image processing, aliasing can manifest as jagged edges or moiré patterns in digital images. To prevent aliasing, anti-aliasing filters are often used before sampling to remove or attenuate frequencies above the Nyquist limit.