Signal processing

Signal processing is the analysis, interpretation and manipulation of signals. Signals of interest include sound, images, biological signals such as ECG, radar signals, and many others.

Processing of such signals includes storage and reconstruction, separation of information from noise (e.g., aircraft identification by radar), compression (e.g., image compression), and feature extraction (e.g., converting text to speech).

For analog signals, signal processing may involve the amplification and filtering of audio signals for audio equipment or the modulation and demodulation of signals for telecommunication. For digital signals, signal processing may involve the compression, error checking and error detection of digital signals.

• Analog signal processing—for signals that have not been digitized, as in classical radio, telephone, radar, and television systems
• Digital signal processing—for signals that have been digitized. Processing is done by digital circuits such as ASICs, FPGAs, general-purpose microprocessors or computers, or specialized digital signal processor chips.
• Statistical signal processing—analyzing and extracting information from signals based on their statistical properties
• Audio signal processing—for electrical signals representing sound, such as music
• Speech signal processing—for processing and interpreting spoken words
• Image processing—in digital cameras, computers, and various imaging systems
• Video signal processing—for interpreting moving pictures
• Array processing—for processing signals from arrays of sensors

Signal processing is the analysis, interpretation and manipulation of acquired signals. Acquired signals must to be processed depending on the purpose of measurement, a method of measurement, and a property of acquired signals.

When signals are processed, statistics is used because it's essential to know a distribution of data and represent data by numerical formulas. In other words, to study signal processing, it's demanded to study statistics (like the theory of error, the arithmetical mean, probability, a stochastic variable, accuracy, and detailed drawing, etc.).

In most cases, signals are regular, as it is acquired from electric instruments like telemeter, or communications equipment, etc. But there are also many accidentally occurred irregular signals which make it difficult to find formulas that fit exactly. Here, the irregular means it's hard to predict the result which is not yet occurred. When irregular signals are acquired, photon is necessary, so it is measured, and calculated.

• Signal (electrical engineering)