PRE-RINGING

What is pre-ringing?

Pre-ringing refers to the impulse response of linear phase filters that are in DA or AD converters be used. Pre-ringing occurs when the filter affects the signal before the actual frequency range you want to process. This can happen too unwanted artifacts that sound like an echo or floating noise before the main signal appears. In some cases this may affect the clarity and naturalness of the sound.
Post ringing equalizer
Post-ringing - normal impulse response of a minimal phasing equalizer

How does pre-ringing occur?

Pre-ringing is primarily caused by the use of linear phase filters in digital signal processing. These filters are often used in digital equalizers and other audio processors. Linear phase filters are used to ensure that the phase relationship between the different frequency components of the signal is maintained. However, when narrow band filters are used to affect specific frequencies, linear phase filters can cause the filter to intervene before the actual frequency range, thus creating pre-ringing. This happens because the filter tries to maintain the phase relationship between different parts of the signal, resulting in unwanted pre-reverb effects .

 

All linear phase EQs result in one Total delay of the signal, which is automatically compensated for by the DAW. When the DAW compensates for this delay, it creates an artifact called pre-ring.

 

With subtle EQ changes, this effect can be ignored. However, with higher Q values, steep filter slopes and large gain changes, the effect becomes more audible. Additionally, higher resolution processing modes (for better low frequency response) result in higher latency, making the pre-ring effect even more pronounced.

Pre-ringing equalizer
Pre-ringing - delay in the impulse response, as well as a clearly visible wave before the actual main impulse

When does a linear phase filter make sense?

Linear phase filters are particularly useful in situations where the phase relationship between the various frequency components of a signal is important, such as: b. mixing or Mastering of music, where phase information can influence spatial perception and sound quality. They are often used when it comes to maintaining the transparency and naturalness of the sound. Linear phase filters are also useful in situations where Phase shifts should be avoided, e.g. B. when using Multiband compressors or -Limitersto shape the signal without affecting spatial perception.

When do linear phase filters not produce pre-ringing?

Linear phase filters typically do not produce pre-ringing when on wide frequency ranges be applied, especially if the Filter slope is not extremely high. Pre-ringing often occurs when narrow band filters with high slopes are used to process specific frequency ranges.

 

The following video explains well when no pre-ringing occurs.

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