Loudness

1
Loudness
Introduction to Acoustics

• University of Salford
• Acoustics, Audio Video Group

2
Learning Outcomes

• Sketch the frequency response of a normal ear
• Explain the relationship between intensity and
  sound pressure level
• Calculate the loudness level of a pure tone

3
Questions

• How is the ear different from a microphone?
• What is the frequency range of the ear?
• What is the intensity range (in decibels)?

4
Equal loudness contours

• Each contour describes a constant loudness level
• Response of the ear is not constant with
  frequency!
• Curves found from experiments
• Loudness level is measured in phons

5
Loudness questions

• What loudness level is produced by a pure tone of
  1000 Hz at a SPL of 40 dB?
• What loudness level is produced by a pure tone of
  50 Hz at a SPL of 40 dB?
• Which sounds louder 4000 Hz at 70 dB or 40 Hz at
  90 dB?
• Over what frequency range is the ear most
  sensitive?

6
Conclusions

• Intensity vs. frequency characteristics described
  by the equal loudness contours
• Response of the ear is not constant with
  frequency!
• Loudness is a subjective effect
• The ear is most sensitive over the main frequency
  range for speech.