Page 45 - Summer 2018

Matthew B. Winn
Address:
Department of Speech & Hearing Sciences University of Washington 1417 NE 42nd Street Seattle, Washington 98105 USA
Email:
mwinn83@gmail.com
Address after August 2018:
Speech-Language-Hearing Sciences Department University of Minnesota 164 Pillsbury Drive SE Minneapolis, Minnesota 55455 USA
Email:
mwinn@umn.edu
Speech: It’s Not as Acoustic as You Think
There are many ways that we understand speech by paying attention to things other than what is spoken.
The waveforms patterns bounced up and down as if to evade my grasp. Spectrograms, supposedly there to help me quantify the exact difference between one vowel and the next, instead seemed to mock me with their peculiar and elusive patterns, changing with every utterance and every talker. Was it possible to really crack the speech code? The deeper I looked, at each frequency and each millisecond of speech, the farther I felt from understanding actual speech communication. My head recoiling in frustration, I sighed and turned away from the computer screen. As it turned out, looking away from the acoustic signal was a step in the right direction.
There is a humbling paradox of studying speech acoustics, which is that speech communication seems so rapid, effortless, and universal, yet scientific inquiry into the topic is overflowing with challenges and a vast ocean of unknowns (for a fur- ther discussion of this, see the article by de Jong in this issue of Acoustics Today). The history of speech science is full of investigators tortured by the exhaustive search for the understanding of speech based on the acoustic signal itself. What could be more satisfying than to decode the key elemental sounds that make up the way humans communicate, absorb news, greet friends, tell jokes, and express thoughts? Best of all, the science of speech acoustics would provide objectivity. The utterance is familiar, and it can be measured in numerous ways. There is no need for subjective or enigmatic forays into the world of linguistic structure, hazy impressions of what is proper or improper, or indeterminate variations in mean- ing and intention. If humans speak the sound, it should be possible to decode it with meticulous attention to the measurements. There is a kind of comfort in the nitty-gritty, irrefutable measurements of sound pressure, frequency, and duration.
But it is possible to let this deep pursuit temporarily obstruct the view of the full expanse of the information used to understand speech, and there is also a risk of having too narrow a scope of what information should be regarded as essential to the communication process. With that in mind, this article is about how spoken language is not as acoustic as one might think. The number of ways that we take in and use information to interpret speech, apart from hearing the acoustic details of the signal, is staggering, and inspiring, especially to this author who identifies as an auditory scientist. Some examples are unsurprising, but others might stun you. The hope is that we can search for a more complete understanding of speech by paying special attention to the parts that are actually unspoken.
To begin with, it should be noted that there is a good deal of useful information to be gleaned from the speech signal itself. A listener succeeds most when the frequency range of speech is audible and when there is sufficient perception of
©2018 Acoustical Society of America. All rights reserved. volume 14, issue 2 | Summer 2018 | Acoustics Today | 43