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Exam 1999 Question 4

"Explain what is meant by the frequency response of a system. Describe an experiment in which the frequency response of a simple resonator is measured. How is the bandwidth of a simple resonator related to the rate of energy lost from the resonator during vibration?"

20 things you should mention:

  • Frequency Response
    • tells us how the system deals with signals passed through it
    • response is ratio of output amplitude to input amplitude
    • can measure it for some frequencies using a sinusoid at that frequency
    • frequency response graph is a graph of the response - axes
    • - measured for different sinusoidal frequencies
    • what system can do to a signal / examples / pictures
    • natural resonant frequency
  • Measurement
    • e.g. an acoustic resonator/pendulum
    • input: sinusoid generator
    • fixed amplitude, variable frequency
    • pass through system, e.g. loudspeaker, microphone
    • output: millivoltmeter
    • calculate response, express in dB
    • plot graph, example picture
    • measure bandwidth
    • - from 3dB points
  • Bandwidth/Time response
    • wide bandwidth = wide range of frequencies giving moderate response
    • rapid loss of energy from system, high damping
    • narrow bandwidth = narrow range of frequencies giving large response
    • energy retained in system, less damping

© 2000 Mark Huckvale University College London