Exam Question Checklist

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