Audio signal processing, sometimes referred to as audio processing, is the processing of a representation of auditory signals, or sound. Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies In the fields of communications, Signal processing, and in Electrical engineering more generally a signal is any time-varying or spatial-varying quantity Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies The representation can be digital or analog. A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for An analog or analogue signal is any continuous signal for which the time varying feature (variable of the signal is a representation of some other
The focus in audio signal processing is most typically a mathematical analysis of which parts of the signal are audible. For example, a signal can be modified for different purposes such that the modification is controlled in the auditory domain.
Which parts of the signal are heard and which are not is determined both by physiology of the human hearing system and by human psychology. Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Psychology (from Greek grc ψῡχή psȳkhē, "breath life soul" and grc -λογία -logia) is an Academic and These properties are analysed within the field of psychoacoustics. Psychoacoustics is the study of subjective human Perception of Sounds Alternatively it can be described as the study of the Psychological correlates
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History of audio processing
Audio processing was necessary for early radio broadcasting -- as there were many problems with studio to transmitter links. This article is about radio broadcasting for other uses see Radio (disambiguation.
Analog signals
An analog representation is usually electrical; a voltage level represents the air pressure waveform of the sound. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical waveformogg|right|a sine square and sawtooth wave at 440 hz]] Waveform means the shape and form of a signal such as a Wave moving in a solid liquid or gaseous
Digital signals
A digital representation expresses the pressure wave-form as a sequence of symbols, usually binary numbers, which permits digital signal processing. The binary numeral system, or base-2 number system, is a Numeral system that represents numeric values using two symbols usually 0 and 1. Digital signal processing ( DSP) is concerned with the representation of the signals by a sequence of numbers or symbols and the processing of these signals Whilst all real-world audio signals are continuous-time and continuous-level analog signals, the frequency range of these signals is limited by physical effects, and human ears cannot perceive frequencies below approx. 20 Hz or above approx. 18 kHz (strongly depends on the age of the listener). Therefore, there is no significant loss of information when the analog signal is sampled using a high enough sampling rate (see: sampling). In Signal processing, sampling is the reduction of a Continuous signal to a Discrete signal. In addition, the dynamic range of audio signals is limited by Noise (sound). is a one volume manga created by Tsutomu Nihei as a prequel to his ten-volume work Blame!. More than 130 dB Signal-to-noise ratio is almost impossible to achieve. Signal-to-noise ratio (often abbreviated SNR or S/N) is an Electrical engineering concept also used in other fields (such as scientific Measurements Therefore, quantization also does not result in significant loss of information either, if done appropriately. In Digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values by a relatively-small Both sampling and quantization must be applied to convert the continuous-time analog signal to a discrete-time digital representation. In Signal processing, sampling is the reduction of a Continuous signal to a Discrete signal. In Signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values by a relatively-small set of Although such a conversion is more or less lossy, most modern audio systems use this approach as the techniques of digital signal processing are much more powerful and efficient than analog domain signal processing. Digital signal processing ( DSP) is concerned with the representation of the signals by a sequence of numbers or symbols and the processing of these signals
Application areas
Processing methods and application areas include storage, level compression, data compression, transmission, enhancement (e. Dynamic range compression, also called DRC (often seen in DVD player settings or simply compression, is a process that reduces the Dynamic range of For processes which reduce the amount of time it takes to listen to and understand a recording see Time-compressed speech. In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or g. , equalization, filtering, noise cancellation, echo or reverb removal or addition, etc. Equalization (or equalisation, EQ) is the process of changing the frequency envelope of a sound in Audio processing. An audio filter is a type of filter used for processing Sound signals. Active noise control (ANC (also known as noise cancellation, active noise reduction (ANR or antinoise) is a method for reducing unwanted Sound In Audio signal processing and Acoustics, an echo (plural echoes) is a reflection of sound arriving at the listener some time after the direct Reverberation is the persistence of Sound in a particular space after the original sound is removed )
Audio Broadcasting
Audio broadcasting (be it for television or audio broadcasting) is perhaps the biggest market segment (and user area) for audio processing products -- globally. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic
Traditionally the most important audio processing (in audio broadcasting) takes place just before the transmitter. Studio audio processing is limited in the modern era due to digital audio systems (mixers, routers) being pervasive in the studio.
In audio broadcasting, the audio processor must
- prevent overmodulation, and minimize it when it occurs
- maximize overall loudness
- compensate for non-linear transmitters, more common with medium wave and shortwave broadcasting
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