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 Duration (ms) d’ relative to 20 ms Large improvement in F0 discrimination with duration for unresolved harmonics (White and Plack, 1998):

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 Stevens, Volkmann & Newmann, 1937 Solid line: mel scale /2.83 Black squares: integrated difference limens Open circles: relative location of the resonant positions on the basilar membrane

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 Cross-Correlation Models  Y (  )= 1/(t 1 -t 0 ) Y(t)Y(t+  )  t=t 0 t1t1 Licklider (1951)

Pitch perception of formant-like sounds (from: de Cheveigne, 2004) Can evoke two pitches Diagonal line sinusoids

Which harmonic determines pitch? from: Chris Darwin Time (t) Period = 1/200 s = 5ms Frequency (Hz) Amplitude Harmonic spacing = 200 Hz Fundamental = 200 Hz Pressure

Pitch remains the same without fundamental (Licklider, 1956): from: Chris Darwin Time (t) Period = 1/200 s = 5ms Frequency (Hz) Harmonic spacing = 200 Hz Pressure Amplitude

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 (formant-glide) and fundamental frequency (micro-intonation). The prefix, an onset of a sound quite dissimilar to the ensuing lasting vibration. Schouten, 1968