nollpassering

A nollpassering, literally meaning "zero crossing" in Swedish, refers to a point where a waveform or signal transitions from a positive value to a negative value, or vice versa. This occurs when the signal's amplitude crosses the zero point of its vertical axis.

In signal processing, nollpassering is a fundamental concept. Identifying these crossings is crucial for various applications. For instance, in digital signal processing, counting the number of zero crossings within a given time interval can provide information about the frequency of a signal. A higher frequency signal will typically have more zero crossings than a lower frequency signal over the same duration. This technique can be used for simple frequency estimation or for detecting the presence of specific frequencies.

Zero crossings are also important in audio processing, where they can be used to synchronize different audio streams or to detect the beginning or end of musical notes. In control systems, zero crossings can indicate changes in the direction of a system's output, which can be used for feedback mechanisms. The precise detection of a nollpassering is often achieved using algorithms that compare the sign of consecutive signal samples. When the sign changes, a zero crossing is detected.