{"id":34251,"date":"2017-08-28T04:39:10","date_gmt":"2017-08-28T09:39:10","guid":{"rendered":"http:\/\/languagelog.ldc.upenn.edu\/nll\/?p=34251"},"modified":"2017-08-28T21:19:48","modified_gmt":"2017-08-29T02:19:48","slug":"pitch-contour-perception","status":"publish","type":"post","link":"https:\/\/languagelog.ldc.upenn.edu\/nll\/?p=34251","title":{"rendered":"Pitch contour perception"},"content":{"rendered":"

Listen to this brief four-syllable phrase, and answer a simple question:<\/p>\n

once the eggs hatch<\/span><\/p>\n

Is the end of the last sylllable (\"hatch\") higher or lower in pitch than the start of the first sylllable (\"once\")?<\/p>\n


\nIf you're like most people, you hear \"hatch\" as ending somewhat higher than \u00a0than the syllables that precede it, though it's also a little rough in voice quality.<\/p>\n

But in purely physical terms, the syllable \"once\" begins at about 200 Hz (= cycles per second) and ends at about 240 Hz, while the syllable \"hatch\" starts at about 100 Hz and ends at about 121 Hz, a full octave lower:<\/p>\n

<\/a><\/a><\/p>\n

Thus an f0 track of the whole thing looks like this:<\/p>\n

<\/a><\/p>\n

This is a good example of one of the reasons that (the psychological dimension of) pitch<\/em> is not the same as the (physical dimenion of) fundamental frequency<\/em>.<\/p>\n

So what's going on here? Why does it sound (to most people) like \"hatch\" is a little higher than \"once\"?<\/p>\n

In acoustic terms, we're hearing the second, fourth, sixth, … harmonics of \"hatch\" as a continuation of the first, second, third, … harmonics of \"once\". In the spectrogram below, I've outlined the third harmonic of \"once\" and the sixth harmonic of \"hatch\":<\/p>\n

<\/a><\/p>\n

In articulatory terms, the octave shift in the last syllable (and also in part of the syllable \"egg\") is an example of something that's a feature of many oscillatory systems, which can undergo period doubling bifurcations<\/a> as a natural consequence of the process that causes them to oscillate in the first place. This happens not only to speakers but also to wind, reed, and brass players, and also happens\u00a0in many processes that don't involve humans at all<\/a>.<\/p>\n

On the perceptual side, this is \u00a0related to the illusions known as Shepard Tones<\/a>\u00a0or Shepard-Risset Glissandos<\/a>, which are sort of auditory barber-pole illusions that also depend on octave-related ambiguities.<\/p>\n

In the example phrase \"once the eggs hatch\", everything works out as it should, because what we hear is pretty much what the speaker intended.<\/p>\n

But of course there are perceptual octave ambiguities in cases where there's no speaker intent to decode. Here's a tone glide that\u00a0starts at 200 Hz and ends at 140 Hz, but sounds to most people as if it's rising throughout:<\/p>\n

It blends a higher rise from 200 to 280 Hz with a lower rise from 100 to 140 Hz:<\/p>\n\n\n\n\n
200-280<\/strong><\/td>\n100-140<\/strong><\/td>\n<\/tr>\n