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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Signal processing</span></span>
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</style><div role="note" class="hatnote navigation-not-searchable">"Signal theory" redirects here; not to be confused with <a href="Signalling_theory" title="Signalling theory">Signalling theory</a> or <a href="Signalling_(economics)" title="Signalling (economics)">Signalling (economics)</a>.</div>
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</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:408px;max-width:408px"><div class="trow"><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><span></span></span></div></div><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><span></span></span></div></div></div><div class="trow" style="display:flex"><div class="thumbcaption">The signal on the left looks like noise, but the signal processing technique known as <a href="Spectral_density_estimation" title="Spectral density estimation">spectral density estimation</a> (right) shows that it contains five well-defined frequency components.</div></div></div></div>
<p><b>Signal processing</b> is an <a href="Electrical_engineering" title="Electrical engineering">electrical engineering</a> subfield that focuses on analyzing, modifying and synthesizing <i><a href="Signal" title="Signal">signals</a></i>, such as <a href="Audio_signal_processing" title="Audio signal processing">sound</a>, <a href="Image_processing" class="mw-redirect" title="Image processing">images</a>, <a href="Scalar_potential" title="Scalar potential">potential fields</a>, <a href="Seismic_tomography" title="Seismic tomography">seismic signals</a>, <a href="Altimeter" title="Altimeter">altimetry processing</a>, and <a href="Scientific_measurements" class="mw-redirect" title="Scientific measurements">scientific measurements</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Signal processing techniques are used to optimize transmissions, <a href="Data_storage" title="Data storage">digital storage</a> efficiency, correcting distorted signals, improve <a href="Subjective_video_quality" title="Subjective video quality">subjective video quality</a>, and to detect or pinpoint components of interest in a measured signal.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>
</p>
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<div class="mw-heading mw-heading2"><h2 id="History">History</h2></div>
<p>According to <a href="Alan_V._Oppenheim" title="Alan V. Oppenheim">Alan V. Oppenheim</a> and <a href="Ronald_W._Schafer" title="Ronald W. Schafer">Ronald W. Schafer</a>, the principles of signal processing can be found in the classical <a href="Numerical_analysis" title="Numerical analysis">numerical analysis</a> techniques of the 17th century. They further state that the digital refinement of these techniques can be found in the digital <a href="Control_system" title="Control system">control systems</a> of the 1940s and 1950s.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>
</p><p>In 1948, <a href="Claude_Shannon" title="Claude Shannon">Claude Shannon</a> wrote the influential paper "<a href="A_Mathematical_Theory_of_Communication" title="A Mathematical Theory of Communication">A Mathematical Theory of Communication</a>" which was published in the <i><a href="Bell_System_Technical_Journal" class="mw-redirect" title="Bell System Technical Journal">Bell System Technical Journal</a></i>.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The paper laid the groundwork for later development of information communication systems and the processing of signals for transmission.<sup id="cite_ref-fifty_5-0" class="reference"><a href="#cite_note-fifty-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>
</p><p>Signal processing matured and flourished in the 1960s and 1970s, and <a href="Digital_signal_processing" title="Digital signal processing">digital signal processing</a> became widely used with specialized <a href="Digital_signal_processor" title="Digital signal processor">digital signal processor</a> chips in the 1980s.<sup id="cite_ref-fifty_5-1" class="reference"><a href="#cite_note-fifty-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading2"><h2 id="Definition_of_a_signal">Definition of a signal</h2></div>
<p>A signal is a <a href="Function_(mathematics)" title="Function (mathematics)">function</a> <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle x(t)}">
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</p>
<ul><li>deterministic (then one speaks of a deterministic signal) or</li>
<li>a path <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle (x_{t})_{t\in T}}">
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<div class="mw-heading mw-heading2"><h2 id="Categories">Categories</h2></div>
<div class="mw-heading mw-heading3"><h3 id="Analog">Analog</h3></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Analog_signal_processing" title="Analog signal processing">Analog signal processing</a></div>
<p>Analog signal processing is for signals that have not been digitized, as in most 20th-century <a href="Radio" title="Radio">radio</a>, telephone, and television systems. This involves linear electronic circuits as well as nonlinear ones. The former are, for instance, <a href="Passive_filter" class="mw-redirect" title="Passive filter">passive filters</a>, <a href="Active_filter" title="Active filter">active filters</a>, <a href="Electronic_mixer" title="Electronic mixer">additive mixers</a>, <a href="Integrator" title="Integrator">integrators</a>, and <a href="Analog_delay_line" title="Analog delay line">delay lines</a>. Nonlinear circuits include <a href="Compandor" class="mw-redirect" title="Compandor">compandors</a>, multipliers (<a href="Frequency_mixer" title="Frequency mixer">frequency mixers</a>, <a href="Voltage-controlled_amplifier" class="mw-redirect" title="Voltage-controlled amplifier">voltage-controlled amplifiers</a>), <a href="Voltage-controlled_filter" title="Voltage-controlled filter">voltage-controlled filters</a>, <a href="Voltage-controlled_oscillator" title="Voltage-controlled oscillator">voltage-controlled oscillators</a>, and <a href="Phase-locked_loop" title="Phase-locked loop">phase-locked loops</a>.
</p>
<div class="mw-heading mw-heading3"><h3 id="Continuous_time">Continuous time</h3></div>
<p><a href="Continuous_signal" class="mw-redirect" title="Continuous signal">Continuous-time signal</a> processing is for signals that vary with the change of continuous domain (without considering some individual interrupted points).
</p><p>The methods of signal processing include <a href="Time_domain" title="Time domain">time domain</a>, <a href="Frequency_domain" title="Frequency domain">frequency domain</a>, and <a href="Complex_frequency" class="mw-redirect" title="Complex frequency">complex frequency domain</a>. This technology mainly discusses the modeling of a <a href="Linear_time-invariant" class="mw-redirect" title="Linear time-invariant">linear time-invariant</a> continuous system, integral of the system's zero-state response, setting up system function and the continuous time filtering of deterministic signals. For example, in time domain, a continuous-time signal <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle x(t)}">
<semantics>
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<annotation encoding="application/x-tex">{\displaystyle x(t)}</annotation>
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</math></span><img src="./d54c275db3a1e620737b58e143b0818107fa5f5c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:3.979ex; height:2.843ex;" alt="{\displaystyle x(t)}" loading="lazy"></span> passing through a <a href="Linear_time-invariant" class="mw-redirect" title="Linear time-invariant">linear time-invariant</a> filter/system denoted as <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle h(t)}">
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<annotation encoding="application/x-tex">{\displaystyle h(t)}</annotation>
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</math></span><img src="./66abbb8ae1d9f30bb529739b109e1e5bbe83c626.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:3.988ex; height:2.843ex;" alt="{\displaystyle h(t)}" loading="lazy"></span>, can be expressed at the output as
</p><p><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle y(t)=\int _{-\infty }^{\infty }h(\tau )x(t-\tau )\,d\tau }">
<semantics>
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<mstyle displaystyle="true" scriptlevel="0">
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<annotation encoding="application/x-tex">{\displaystyle y(t)=\int _{-\infty }^{\infty }h(\tau )x(t-\tau )\,d\tau }</annotation>
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</math></span><img src="./f7346d6decd983238af39e135de7ee4ab334a31b.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:26.912ex; height:6.009ex;" alt="{\displaystyle y(t)=\int _{-\infty }^{\infty }h(\tau )x(t-\tau )\,d\tau }" loading="lazy"></span>
</p><p>In some contexts, <span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle h(t)}">
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<annotation encoding="application/x-tex">{\displaystyle h(t)}</annotation>
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</math></span><img src="./66abbb8ae1d9f30bb529739b109e1e5bbe83c626.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:3.988ex; height:2.843ex;" alt="{\displaystyle h(t)}" loading="lazy"></span> is referred to as the impulse response of the system. The above <a href="Convolution" title="Convolution">convolution</a> operation is conducted between the input and the system.
</p>
<div class="mw-heading mw-heading3"><h3 id="Discrete_time">Discrete time</h3></div>
<p><a href="Discrete-time_signal" class="mw-redirect" title="Discrete-time signal">Discrete-time signal</a> processing is for sampled signals, defined only at discrete points in time, and as such are quantized in time, but not in magnitude.
</p><p><i>Analog discrete-time signal processing</i> is a technology based on electronic devices such as <a href="Sample_and_hold" title="Sample and hold">sample and hold</a> circuits, analog time-division <a href="Multiplexer" title="Multiplexer">multiplexers</a>, <a href="Analog_delay_line" title="Analog delay line">analog delay lines</a> and <a href="Analog_feedback_shift_register" title="Analog feedback shift register">analog feedback shift registers</a>. This technology was a predecessor of digital signal processing (see below), and is still used in advanced processing of gigahertz signals.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup>
</p><p>The concept of discrete-time signal processing also refers to a theoretical discipline that establishes a mathematical basis for digital signal processing, without taking <a href="Quantization_error" class="mw-redirect" title="Quantization error">quantization error</a> into consideration.
</p>
<div class="mw-heading mw-heading3"><h3 id="Digital">Digital</h3></div>
<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Digital_signal_processing" title="Digital signal processing">Digital signal processing</a></div>
<p>Digital signal processing is the processing of digitized discrete-time sampled signals. Processing is done by general-purpose <a href="Computer" title="Computer">computers</a> or by digital circuits such as <a href="ASIC" class="mw-redirect" title="ASIC">ASICs</a>, <a href="Field-programmable_gate_array" title="Field-programmable gate array">field-programmable gate arrays</a> or specialized <a href="Digital_signal_processor" title="Digital signal processor">digital signal processors</a>. Typical arithmetical operations include <a href="Fixed-point_arithmetic" title="Fixed-point arithmetic">fixed-point</a> and <a href="Floating-point" class="mw-redirect" title="Floating-point">floating-point</a>, real-valued and complex-valued, multiplication and addition. Other typical operations supported by the hardware are <a href="Circular_buffer" title="Circular buffer">circular buffers</a> and <a href="Lookup_table" title="Lookup table">lookup tables</a>. Examples of algorithms are the <a href="Fast_Fourier_transform" title="Fast Fourier transform">fast Fourier transform</a> (FFT), <a href="Finite_impulse_response" title="Finite impulse response">finite impulse response</a> (FIR) filter, <a href="Infinite_impulse_response" title="Infinite impulse response">Infinite impulse response</a> (IIR) filter, and <a href="Adaptive_filter" title="Adaptive filter">adaptive filters</a> such as the <a href="Wiener_filter" title="Wiener filter">Wiener</a> and <a href="Kalman_filter" title="Kalman filter">Kalman filters</a>.
</p>
<div class="mw-heading mw-heading3"><h3 id="Nonlinear">Nonlinear</h3></div>
<p>Nonlinear signal processing involves the analysis and processing of signals produced from <a href="Nonlinear_system" title="Nonlinear system">nonlinear systems</a> and can be in the time, <a href="Frequency" title="Frequency">frequency</a>, or spatiotemporal domains.<sup id="cite_ref-Billings_8-0" class="reference"><a href="#cite_note-Billings-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-VSA_9-0" class="reference"><a href="#cite_note-VSA-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Nonlinear systems can produce highly complex behaviors including <a href="Bifurcation_theory" title="Bifurcation theory">bifurcations</a>, <a href="Chaos_theory" title="Chaos theory">chaos</a>, <a href="Harmonics" class="mw-redirect" title="Harmonics">harmonics</a>, and <a href="Subharmonics" class="mw-redirect" title="Subharmonics">subharmonics</a> which cannot be produced or analyzed using linear methods.
</p><p>Polynomial signal processing is a type of non-linear signal processing, where <a href="Polynomial" title="Polynomial">polynomial</a> systems may be interpreted as conceptually straightforward extensions of linear systems to the nonlinear case.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading3"><h3 id="Statistical">Statistical</h3></div>
<p><b>Statistical signal processing</b> is an approach which treats signals as <a href="Stochastic_process" title="Stochastic process">stochastic processes</a>, utilizing their <a href="Statistical" class="mw-redirect" title="Statistical">statistical</a> properties to perform signal processing tasks.<sup id="cite_ref-Scharf_11-0" class="reference"><a href="#cite_note-Scharf-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Statistical techniques are widely used in signal processing applications. For example, one can model the <a href="Probability_distribution" title="Probability distribution">probability distribution</a> of noise incurred when photographing an image, and construct techniques based on this model to <a href="Noise_reduction" title="Noise reduction">reduce the noise</a> in the resulting image.
</p>
<div class="mw-heading mw-heading3"><h3 id="Graph">Graph</h3></div>
<p><b>Graph signal processing</b> generalizes signal processing tasks to signals living on non-Euclidean domains whose structure can be captured by a weighted graph.<sup id="cite_ref-Ortega_12-0" class="reference"><a href="#cite_note-Ortega-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> Graph signal processing presents several key points such as sampling signal techniques,<sup id="cite_ref-Tanaka_13-0" class="reference"><a href="#cite_note-Tanaka-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> recovery techniques <sup id="cite_ref-Fascista_14-0" class="reference"><a href="#cite_note-Fascista-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> and time-varying techiques.<sup id="cite_ref-Giraldo_15-0" class="reference"><a href="#cite_note-Giraldo-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> Graph signal processing has been applied with success in the field of image processing, computer vision <sup id="cite_ref-Giraldo1_16-0" class="reference"><a href="#cite_note-Giraldo1-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>
<sup id="cite_ref-Giraldo2_17-0" class="reference"><a href="#cite_note-Giraldo2-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup>
<sup id="cite_ref-Giraldo3_18-0" class="reference"><a href="#cite_note-Giraldo3-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> and sound anomaly detection.<sup id="cite_ref-Bouwmans1_19-0" class="reference"><a href="#cite_note-Bouwmans1-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup>
</p>
<div class="mw-heading mw-heading2"><h2 id="Application_fields">Application fields</h2></div>
<ul><li><a href="Audio_signal_processing" title="Audio signal processing">Audio signal processing</a> – for electrical signals representing sound, such as <a href="Speech_signal_processing" class="mw-redirect" title="Speech signal processing">speech</a> or music<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Image_processing" class="mw-redirect" title="Image processing">Image processing</a> – in digital cameras, computers and various imaging systems</li>
<li><a href="Video_processing" title="Video processing">Video processing</a> – for interpreting moving pictures</li>
<li><a href="Wireless_communication" class="mw-redirect" title="Wireless communication">Wireless communication</a> – waveform generations, demodulation, filtering, equalization</li>
<li><a href="Control_systems" class="mw-redirect" title="Control systems">Control systems</a></li>
<li><a href="Array_processing" title="Array processing">Array processing</a> – for processing signals from arrays of sensors</li>
<li><a href="Process_control" class="mw-redirect" title="Process control">Process control</a> – a variety of signals are used, including the industry standard <a href="4-20_mA_current_loop" class="mw-redirect" title="4-20 mA current loop">4-20 mA current loop</a></li>
<li><a href="Seismology" title="Seismology">Seismology</a></li>
<li><a href="Feature_extraction" class="mw-redirect" title="Feature extraction">Feature extraction</a>, such as <a href="Image_understanding" class="mw-redirect" title="Image understanding">image understanding</a>, <a href="Semantic_audio" title="Semantic audio">semantic audio</a> and <a href="Speech_recognition" title="Speech recognition">speech recognition</a>.</li>
<li>Quality improvement, such as <a href="Noise_reduction" title="Noise reduction">noise reduction</a>, <a href="Image_enhancement" class="mw-redirect" title="Image enhancement">image enhancement</a>, and <a href="Echo_cancellation" class="mw-redirect" title="Echo cancellation">echo cancellation</a>.</li>
<li>Source coding including <a href="Audio_compression_(data)" class="mw-redirect" title="Audio compression (data)">audio compression</a>, <a href="Image_compression" title="Image compression">image compression</a>, and <a href="Video_compression" class="mw-redirect" title="Video compression">video compression</a>.</li>
<li><a href="Genomic" class="mw-redirect" title="Genomic">Genomic</a> signal processing<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup></li>
<li>In <a href="Geophysics" title="Geophysics">geophysics</a>, signal processing is used to amplify the signal vs the noise within <a href="Time-series" class="mw-redirect" title="Time-series">time-series</a> measurements of geophysical data. Processing is conducted within the <a href="Time_domain" title="Time domain">time domain</a> or <a href="Frequency_domain" title="Frequency domain">frequency domain</a>, or both.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup></li></ul>
<p>In communication systems, signal processing may occur at:
</p>
<ul><li>OSI layer 1 in the seven-layer <a href="OSI_model" title="OSI model">OSI model</a>, the <a href="Physical_layer" title="Physical layer">physical layer</a> (<a href="Modulation" class="mw-redirect" title="Modulation">modulation</a>, <a href="Equalization_(communications)" title="Equalization (communications)">equalization</a>, <a href="Multiplexing" title="Multiplexing">multiplexing</a>, etc.);</li>
<li>OSI layer 2, the <a href="Data_link_layer" title="Data link layer">data link layer</a> (<a href="Forward_error_correction" class="mw-redirect" title="Forward error correction">forward error correction</a>);</li>
<li>OSI layer 6, the <a href="Presentation_layer" title="Presentation layer">presentation layer</a> (source coding, including <a href="Analog-to-digital_conversion" class="mw-redirect" title="Analog-to-digital conversion">analog-to-digital conversion</a> and <a href="Data_compression" title="Data compression">data compression</a>).</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Typical_devices">Typical devices</h2></div>
<ul><li><a href="Filter_(signal_processing)" title="Filter (signal processing)">Filters</a> – for example analog (passive or active) or digital (<a href="FIR_filter" class="mw-redirect" title="FIR filter">FIR</a>, <a href="IIR_filter" class="mw-redirect" title="IIR filter">IIR</a>, frequency domain or <a href="Stochastic_filter" class="mw-redirect" title="Stochastic filter">stochastic filters</a>, etc.)</li>
<li><a href="Sampling_(signal_processing)" title="Sampling (signal processing)">Samplers</a> and <a href="Analog-to-digital_converter" title="Analog-to-digital converter">analog-to-digital converters</a> for <a href="Signal_acquisition" class="mw-redirect" title="Signal acquisition">signal acquisition</a> and reconstruction, which involves measuring a physical signal, storing or transferring it as digital signal, and possibly later rebuilding the original signal or an approximation thereof.</li>
<li><a href="Digital_signal_processor" title="Digital signal processor">Digital signal processors</a> (DSPs)</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Mathematical_methods_applied">Mathematical methods applied</h2></div>
<ul><li><a href="Differential_equations" class="mw-redirect" title="Differential equations">Differential equations</a><sup id="cite_ref-Gaydecki2004_24-0" class="reference"><a href="#cite_note-Gaydecki2004-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> – for modeling system behavior, connecting input and output relations in linear time-invariant systems. For instance, a low-pass filter such as an <a href="RC_circuit" title="RC circuit">RC circuit</a> can be modeled as a differential equation in signal processing, which allows one to compute the continuous output signal as a function of the input or initial conditions.</li>
<li><a href="Recurrence_relation" title="Recurrence relation">Recurrence relations</a><sup id="cite_ref-Engelberg2008_25-0" class="reference"><a href="#cite_note-Engelberg2008-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Transform_theory" title="Transform theory">Transform theory</a></li>
<li><a href="Time-frequency_analysis" class="mw-redirect" title="Time-frequency analysis">Time-frequency analysis</a> – for processing non-stationary signals<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Linear_canonical_transformation" title="Linear canonical transformation">Linear canonical transformation</a></li>
<li><a href="Spectral_estimation" class="mw-redirect" title="Spectral estimation">Spectral estimation</a> – for determining the spectral content (i.e., the distribution of power over frequency) of a set of <a href="Time_series" title="Time series">time series</a> data points<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Statistical_signal_processing" class="mw-redirect" title="Statistical signal processing">Statistical signal processing</a> – analyzing and extracting information from signals and noise based on their stochastic properties</li>
<li><a href="Linear_time-invariant_system" title="Linear time-invariant system">Linear time-invariant system</a> theory, and <a href="Transform_theory" title="Transform theory">transform theory</a></li>
<li><a href="Polynomial_signal_processing" class="mw-redirect" title="Polynomial signal processing">Polynomial signal processing</a> – analysis of systems which relate input and output using polynomials</li>
<li><a href="System_identification" title="System identification">System identification</a><sup id="cite_ref-Billings_8-1" class="reference"><a href="#cite_note-Billings-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> and classification</li>
<li><a href="Calculus" title="Calculus">Calculus</a></li>
<li><a href="Coding_theory" title="Coding theory">Coding theory</a></li>
<li><a href="Complex_analysis" title="Complex analysis">Complex analysis</a><sup id="cite_ref-SchreierScharf2010_28-0" class="reference"><a href="#cite_note-SchreierScharf2010-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Vector_spaces" class="mw-redirect" title="Vector spaces">Vector spaces</a> and <a href="Linear_algebra" title="Linear algebra">Linear algebra</a><sup id="cite_ref-Little2019_29-0" class="reference"><a href="#cite_note-Little2019-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Functional_analysis" title="Functional analysis">Functional analysis</a><sup id="cite_ref-DamelinJr2012_30-0" class="reference"><a href="#cite_note-DamelinJr2012-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Probability" title="Probability">Probability</a> and <a href="Stochastic_processes" class="mw-redirect" title="Stochastic processes">stochastic processes</a><sup id="cite_ref-Scharf_11-1" class="reference"><a href="#cite_note-Scharf-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Detection_theory" title="Detection theory">Detection theory</a></li>
<li><a href="Estimation_theory" title="Estimation theory">Estimation theory</a></li>
<li><a href="Optimization" class="mw-redirect" title="Optimization">Optimization</a><sup id="cite_ref-PalomarEldar2010_31-0" class="reference"><a href="#cite_note-PalomarEldar2010-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup></li>
<li><a href="Numerical_methods" class="mw-redirect" title="Numerical methods">Numerical methods</a></li>
<li><a href="Data_mining" title="Data mining">Data mining</a> – for statistical analysis of relations between large quantities of variables (in this context representing many physical signals), to extract previously unknown interesting patterns</li></ul>
<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<ul><li><a href="Algebraic_signal_processing" title="Algebraic signal processing">Algebraic signal processing</a></li>
<li><a href="Audio_filter" title="Audio filter">Audio filter</a></li>
<li><a href="Bounded_variation" title="Bounded variation">Bounded variation</a></li>
<li><a href="Dynamic_range_compression" title="Dynamic range compression">Dynamic range compression</a></li>
<li><a href="Information_theory" title="Information theory">Information theory</a></li>
<li><a href="Least-squares_spectral_analysis" title="Least-squares spectral analysis">Least-squares spectral analysis</a></li>
<li><a href="Non-local_means" title="Non-local means">Non-local means</a></li>
<li><a href="Reverberation" title="Reverberation">Reverberation</a></li>
<li><a href="Sensitivity_(electronics)" title="Sensitivity (electronics)">Sensitivity (electronics)</a></li>
<li><a href="Similarity_(signal_processing)" title="Similarity (signal processing)">Similarity (signal processing)</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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<li id="cite_note-Bouwmans1-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-Bouwmans1_19-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFMnasriGiraldoBouwmans2024" class="citation journal cs1">Mnasri, Z.; Giraldo, H.; Bouwmans, T. (2024). <a rel="nofollow" class="external text" href="https://ieeexplore.ieee.org/document/10715291">"Anomalous Sound Detection for Road Surveillance based on Graph Signal Processing"</a>. <i>European Conference on Signal Processing, EUSIPCO 2024</i>: <span class="nowrap">161–</span>165. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.23919%2FEUSIPCO63174.2024.10715291">10.23919/EUSIPCO63174.2024.10715291</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-9-4645-9361-7</bdi>.</cite></span>
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<li id="cite_note-Gaydecki2004-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-Gaydecki2004_24-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFPatrick_Gaydecki2004" class="citation book cs1">Patrick Gaydecki (2004). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=6Qo7NvX3vz4C&q=%22differential+equation%22+OR+%22differential+equations%22&pg=PA40"><i>Foundations of Digital Signal Processing: Theory, Algorithms and Hardware Design</i></a>. IET. pp. 40–. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-85296-431-6</bdi>.</cite></span>
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<li id="cite_note-Engelberg2008-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-Engelberg2008_25-0">^</a></b></span> <span class="reference-text"><cite id="CITEREFShlomo_Engelberg2008" class="citation book cs1">Shlomo Engelberg (8 January 2008). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=z3CpcCHbtgIC"><i>Digital Signal Processing: An Experimental Approach</i></a>. Springer Science & Business Media. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1-84800-119-0</bdi>.</cite></span>
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<li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><cite id="CITEREFBoashash,_Boualem2003" class="citation book cs1">Boashash, Boualem, ed. (2003). <i>Time frequency signal analysis and processing a comprehensive reference</i> (1 ed.). Amsterdam: Elsevier. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-08-044335-4</bdi>.</cite></span>
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<li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><cite id="CITEREFStoicaMoses2005" class="citation book cs1">Stoica, Petre; Moses, Randolph (2005). <a rel="nofollow" class="external text" href="http://user.it.uu.se/%7Eps/SAS-new.pdf"><i>Spectral Analysis of Signals</i></a> <span class="cs1-format">(PDF)</span>. NJ: Prentice Hall.</cite></span>
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</li>
</ol></div></div>
<div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2></div>
<ul><li><cite id="CITEREFByrne2014" class="citation book cs1">Byrne, Charles (2014). <a rel="nofollow" class="external text" href="https://www.taylorfrancis.com/books/oa-mono/10.1201/b17672/signal-processing-charles-byrne"><i>Signal Processing: A Mathematical Approach</i></a>. <a href="Taylor_%26_Francis" title="Taylor & Francis">Taylor & Francis</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1201%2Fb17672">10.1201/b17672</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>9780429158711</bdi>.</cite></li>
<li><cite id="CITEREFP_Stoica2005" class="citation book cs1">P Stoica, R Moses (2005). <a rel="nofollow" class="external text" href="https://user.it.uu.se/%7Eps/SAS-new.pdf"><i>Spectral Analysis of Signals</i></a> <span class="cs1-format">(PDF)</span>. NJ: Prentice Hall.</cite></li>
<li><cite id="CITEREFPapoulis1991" class="citation book cs1">Papoulis, Athanasios (1991). <i>Probability, Random Variables, and Stochastic Processes</i> (third ed.). McGraw-Hill. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-07-100870-5</bdi>.</cite></li>
<li>Kainam Thomas Wong <a rel="nofollow" class="external autonumber" href="http://www.eie.polyu.edu.hk/~enktwong/">[1]</a>: Statistical Signal Processing lecture notes at the University of Waterloo, Canada.</li>
<li><a href="Ali_H._Sayed" title="Ali H. Sayed">Ali H. Sayed</a>, Adaptive Filters, Wiley, NJ, 2008, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-470-25388-5</bdi>.</li>
<li><a href="Thomas_Kailath" title="Thomas Kailath">Thomas Kailath</a>, <a href="Ali_H._Sayed" title="Ali H. Sayed">Ali H. Sayed</a>, and <a href="Babak_Hassibi" title="Babak Hassibi">Babak Hassibi</a>, Linear Estimation, Prentice-Hall, NJ, 2000, <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-0-13-022464-4</bdi>.</li></ul>
<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>
<ul><li><a rel="nofollow" class="external text" href="https://www.sp4comm.org/">Signal Processing for Communications</a> – free online textbook by Paolo Prandoni and Martin Vetterli (2008)</li>
<li><a rel="nofollow" class="external text" href="http://www.dspguide.com">Scientists and Engineers Guide to Digital Signal Processing</a> – free online textbook by Stephen Smith</li>
<li><a rel="nofollow" class="external text" href="https://www.dsprelated.com/freebooks/sasp/">Julius O. Smith III: Spectral Audio Signal Processing</a> – free online textbook</li>
<li><a rel="nofollow" class="external text" href="https://sites.google.com/view/gsp-website/graph-signal-processing">Graph Signal Processing Website</a> – free online website by Thierry Bouwmans (2025)</li></ul>
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</style><div id="Digital_signal_processing96" style="font-size:114%;margin:0 4em"><a href="Digital_signal_processing" title="Digital signal processing">Digital signal processing</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Theory</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Detection_theory" title="Detection theory">Detection theory</a></li>
<li><a href="Discrete_time_and_continuous_time" title="Discrete time and continuous time">Discrete signal</a></li>
<li><a href="Estimation_theory" title="Estimation theory">Estimation theory</a></li>
<li><a href="Nyquist%E2%80%93Shannon_sampling_theorem" title="Nyquist–Shannon sampling theorem">Nyquist–Shannon sampling theorem</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Sub-fields</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Audio_signal_processing" title="Audio signal processing">Audio signal processing</a></li>
<li><a href="Digital_image_processing" title="Digital image processing">Digital image processing</a></li>
<li><a href="Speech_processing" title="Speech processing">Speech processing</a></li>
<li><a href="Statistical_signal_processing" class="mw-redirect" title="Statistical signal processing">Statistical signal processing</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Techniques</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Z-transform" title="Z-transform">Z-transform</a>
<ul><li><a href="Advanced_z-transform" title="Advanced z-transform">Advanced z-transform</a></li>
<li><a href="Matched_Z-transform_method" title="Matched Z-transform method">Matched Z-transform method</a></li></ul></li>
<li><a href="Bilinear_transform" title="Bilinear transform">Bilinear transform</a></li>
<li><a href="Constant-Q_transform" title="Constant-Q transform">Constant-Q transform</a></li>
<li><a href="Discrete_cosine_transform" title="Discrete cosine transform">Discrete cosine transform</a> (DCT)</li>
<li><a href="Discrete_Fourier_transform" title="Discrete Fourier transform">Discrete Fourier transform</a> (DFT)</li>
<li><a href="Discrete-time_Fourier_transform" title="Discrete-time Fourier transform">Discrete-time Fourier transform</a> (DTFT)</li>
<li><a href="Impulse_invariance" title="Impulse invariance">Impulse invariance</a></li>
<li><a href="Integral_transform" title="Integral transform">Integral transform</a></li>
<li><a href="Laplace_transform" title="Laplace transform">Laplace transform</a></li>
<li><a href="Post's_inversion_formula" class="mw-redirect" title="Post's inversion formula">Post's inversion formula</a></li>
<li><a href="Starred_transform" title="Starred transform">Starred transform</a></li>
<li><a href="Zak_transform" title="Zak transform">Zak transform</a></li></ul>
</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Sampling_(signal_processing)" title="Sampling (signal processing)">Sampling</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">
<ul><li><a href="Aliasing" title="Aliasing">Aliasing</a></li>
<li><a href="Anti-aliasing_filter" title="Anti-aliasing filter">Anti-aliasing filter</a></li>
<li><a href="Downsampling_(signal_processing)" title="Downsampling (signal processing)">Downsampling</a></li>
<li><a href="Nyquist_rate" title="Nyquist rate">Nyquist rate</a> / <a href="Nyquist_frequency" title="Nyquist frequency">frequency</a></li>
<li><a href="Oversampling" title="Oversampling">Oversampling</a></li>
<li><a href="Quantization_(signal_processing)" title="Quantization (signal processing)">Quantization</a></li>
<li><a href="Sampling_rate" class="mw-redirect" title="Sampling rate">Sampling rate</a></li>
<li><a href="Undersampling" title="Undersampling">Undersampling</a></li>
<li><a href="Upsampling" title="Upsampling">Upsampling</a></li></ul>
</div></td></tr></tbody></table></div>
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