Frequency response is the quantitative measure of the output spectrum of a system or device in response to a stimulus, and is used to characterize the dynamics of the system. It is a measure of magnitude and phase of the output as a function of frequency, in comparison to the input. In simplest terms, if a sine wave is injected into a system at a given frequency, a linear system will respond at that same frequency with a certain magnitude and a certain phase angle relative to the input. Also for a linear system, doubling the amplitude of the input will double the amplitude of the output. In addition, if the system is time-invariant, then the frequency response also will not vary with time.
Two applications of frequency response analysis are related but have different objectives. For an audio system, the objective may be to reproduce the input signal with no distortion. That would require a uniform (flat) magnitude of response up to the bandwidth limitation of the system, with the signal delayed by precisely the same amount of time at all frequencies. That amount of time could be seconds, or weeks or months in the case of recorded media. In contrast, for a feedback apparatus used to control a dynamical system, the objective is to give the closed-loop system improved response as compared to the uncompensated system. The feedback generally needs to respond to system dynamics within a very small number of cycles of oscillation (usually less than one full cycle), and with a definite phase angle relative to the commanded control input. For feedback of sufficient amplification, getting the phase angle wrong can lead to instability for an open-loop stable system, or failure to stabilize a system that is open-loop unstable. Digital filters may be used for both audio systems and feedback control systems, but since the objectives are different, generally the phase characteristics of the filters will be significantly different for the two applications.
Other articles related to "frequency response, frequency":
... Radio spectrum frequency response can refer to measurements of coaxial cable, twisted-pair cable, video switching equipment, wireless communications devices, and antenna systems ... Infrasonic frequency response measurements include earthquakes and electroencephalography (brain waves) ... Frequency response requirements differ depending on the application ...
... A guitar speaker shows a nonlinear frequency response depending on the speakers load, e.g ... the frequency response at small amplitudes is different from those at large amplitudes ... core essence it is equalization which combined with a model of resonance, modeling the frequency response of the speaker as well as the internal ...
... Most electric systems use alternating current with a nominal frequency of 50 or 60 Hz (hertz) to deliver energy produced by electrical generators to the electricity consumers ... of electric power produced by the generators exceeds the power used by the customers, the frequency of the electricity rises ... power produced is less than what is consumed, the frequency drops ...
... Frequency Response Inexpensive transformers may have poor reproduction of low and high frequencies ... are prone to distortion at higher power levels, especially with regard to low frequency response. 200 watts) begin to suffer from high frequency attenuation due to self-capacitance ...
... Frequency response measurements are only meaningful if shown as a graph, or specified in terms of ±3 dB limits (or other limits) ... A power bandwidth measurement is therefore most useful, in addition to frequency response, this being a plot of maximum SPL out for a given distortion figure ... Specifications like 'Frequency response 40 Hz to 18 kHz', which are common, are valueless ...
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