Applied Psychoacoustics
Lecture 4: Pitch & Timbre Perception
Jonas Braasch
Contents
• Pitch perception
– Pure Tones
– Place and Rate Theory
– Complex Tones
• Timbre
Equal Temperament
One semitone equals: 12√2=1.0595=5.9463%
One cent: 1200√2=1.0006=0.059%
Perfect fifth: 1.5=700 cent=50%
Perfect Octave: 2=1200 cent=100%
Effect of signal duration
Large improvement in F0 discrimination with duration for
unresolved harmonics (White and Plack, 1998):
d’ relative to 20 ms
4.5
4
3.5
3
2.5
2
250-Hz F0,
5500-7500 Hz
1.5
1
0.5
0
0
20
40
60
80
100
120
Duration (ms)
140
160
180
Definition of Pitch
Pitch is that attribute of auditory sensation
in terms of which sounds may be ordered on
a scale extending from low to high. Pitch
depends mainly on the frequency content of
the sound stimulus, but it also depends on
the sound pressure and the waveform of the
stimulus.
ANSI standard 1994
The mel scale
Stevens, Volkmann & Newmann, 1937
•Five listeners were
asked to judge a the
frequency of a second
sinusoidal tone
generator
to be perceived half the
Magnitude of the first
oscillator with constant
frequency
(method of
adjustment)
•Sound was switched
between both oscillators
(2-s interval)
•60 dB SPL
Mel Scale
Def.: 1000 mels= 1000 Hz at 40 dB
The mel scale
Stevens, Volkmann & Newmann, 1937
The mel scale
•Solid line: mel scale
/2.83
•Black squares:
integrated
difference limens
•Open circles: relative
location of the resonant
positions on the basilar
membrane
Stevens, Volkmann & Newmann, 1937
Theories on Pitch Perception
• Place Theory
– Pitch is determined by the location of the
firing inner hair cell population on the basilar
membrane
• Rate Theory
– Pitch is determined by the rate code of the
inner hair cells (phase locking)
Autocorrelation
t
Cross-Correlation
Models
YY (t)= 1/(t1-t0)
1
S
Y(t)Y(t+t)
t=t0
Licklider (1951)
Pitch perception of formant-like sounds
•Can evoke two
pitches
•Diagonal line
sinusoids
(from: de Cheveigne, 2004)
Which harmonic determines pitch?
Fundamental = 200 Hz
Harmonic spacing
= 200 Hz
4
2
1
0
1
-1
-2
Amplitude
Pressure
3
-3
-4
Time (t)
Period = 1/200 s = 5ms
from: Chris Darwin
200 400 600 800
Frequency (Hz)
Pitch remains the same without fundamental
(Licklider, 1956):
Harmonic spacing
= 200 Hz
Pressure
2
1
0
1
-1
Amplitude
3
-2
-3
Time (t)
Period = 1/200 s = 5ms
from: Chris Darwin
200 400 600 800
Frequency (Hz)
Absolute Pitch
• "Passive" absolute pitch
– Persons who are able to identify individual notes
which they hear,
– They can typically identify the key of a composition
• "Active" absolute pitch
– Persons with active absolute pitch will be able to sing
any given note when asked.
– Usually, people with active absolute pitch will not only
be able to identify a note, but recognize when that
note is slightly sharp or flat.
Motoric Absolute Pitch
Persons who can reproduce an absolute
reference tone to determine the pitch of other
tones (e.g. professional singer knowing their
range, persons who speak a tone language).
Timbre
Timbre is that attribute of auditory sensation
in terms of which a listener can judge that two
sounds similarly presented and having the
same loudness and pitch are dissimilar.
ANSI, 1960
Elusive attributes of timbre
• The range between tonal and noiselike
character.
• The spectral envelope.
• The time envelope in terms of rise, duration,
and decay.
• The changes both of spectral envelope (formantglide) and fundamental frequency (microintonation).
• The prefix, an onset of a sound quite dissimilar
to the ensuing lasting vibration.
Schouten, 1968