Impulse noise (audio)
Encyclopedia
Impulse noise is a category of (acoustic
) noise
which includes unwanted, almost instantaneous (thus impulse-like) sharp sounds (like clicks and pops). Noises of the kind are usually caused by electromagnetic interference
, scratches on the recording disks, and ill synchronization in digital recording and communication. High levels of such a noise ( 200 + Decibels ) may damage internal organs, while 180 Decibels are enough to destroy or damage human ears.
An impulse noise filter can be used to enhance the quality of noisy signals, in order to achieve robustness in pattern recognition and adaptive control systems. A classic filter used to remove impulse noise is the median
filter, at the expense of signal degradation. Thus it's quite common, in order to get better performing impulse noise filters, to use model-based systems that know the properties of the noise and source signal (in time or frequency), in order to remove only impulse obliterated samples.
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...
) noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
which includes unwanted, almost instantaneous (thus impulse-like) sharp sounds (like clicks and pops). Noises of the kind are usually caused by electromagnetic interference
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
, scratches on the recording disks, and ill synchronization in digital recording and communication. High levels of such a noise ( 200 + Decibels ) may damage internal organs, while 180 Decibels are enough to destroy or damage human ears.
An impulse noise filter can be used to enhance the quality of noisy signals, in order to achieve robustness in pattern recognition and adaptive control systems. A classic filter used to remove impulse noise is the median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
filter, at the expense of signal degradation. Thus it's quite common, in order to get better performing impulse noise filters, to use model-based systems that know the properties of the noise and source signal (in time or frequency), in order to remove only impulse obliterated samples.
See also
- Audio synchronizerAudio synchronizerAn audio synchronizer is a variable audio delay used to correct or maintain audio video sync or timing also known as lip sync error. See for example the specification for audio to video timing given in ATSC Document IS-191...
- Record restorationRecord restorationRecord restoration, a particular kind of audio restoration, is the process of converting theanalog signal stored on gramophone records Record restoration, a particular kind of audio restoration, is the process of converting theanalog signal stored on gramophone records Record restoration, a...