Psychoacoustics

1
Psychoacoustics

• Limits of Perception
• Phase
• Masking Effects
• Auditory Illusions
• Timbre
• Emotion

2
Limits of Perception

• The human ear can nominally hear
• sounds in the range 20 Hz to 20 kHz
• Frequency resolution of the ear
• is, in the middle range, about 2 Hz

3
Limits of Perception(cont.)

• effect of frequency on the human ear has a
  logarithmic basis gt 2f one octave
• the lower limit of audibility is defined to 0 dB
• can be exposed to short periods of 120 dB, but
  long term exposure to 80 dB can cause permanent
  hearing loss

4
Limits of Perception(cont.)

• Absolute Threshold of Hearing (ATH)
• reduced sensitivity to high frequencies,
• which are partially masked by the head
• (in frontal speaker)
• Equal-loudness contours

5
Harmonic interaction

• As two distinct tones move closer together, they
  seem to fuse into one combination tone. There is
  a rough sound before and after this mix

6
Phase

• Human hearing is basically a spectral analyzer -
  the ear resolves the spectral content of the
  pressure wave without respect to the phase of the
  signal
• Inter-aural (i.e. between ears) phase difference
  is a notable exception

7
Masking Effects

• simultaneous masking
• temporal masking
• noises are better masks than sinusoids

8
Auditory Illusions

• Glissando illusion
• McGurk Effect
• Haas Effect
• Deutschs scale illusion
• Shepard tone
• http//www.cs.ubc.ca/nest/imager/contributions/fli
  nn/Illusions/Illusions.html

9
Timbre

• American Standards Association "... that
  attribute of sensation in terms of which a
  listener can judge that two sounds having the
  same loudness and pitch are dissimilar"
• Tone quality, or colour
• http//lcavwww.epfl.ch/prandoni/timbre.html

10
Emotion

• amygdala -gt hypothalamus -gt physiological
  change
• happy -gt major tone sad -gt minor tone