Human Speech Sounds Research Articles

Speech Producing Abilities of Primates and Human Evolution

Comparative anatomic and acoustic studies of the supralaryngeal vocal tracts of living and extinct primates indicate that speech production has been an important factor in human evolution. The sounds of human speech make human language a rapid medium of communication through a process of speech “encoding.” The presence of the human vowels /a/, /i/, and /u/ facilitates this process. The supralaryngeal vocal tracts of newborn Homo sapiens and the living nonhuman primates are similar and resemble the reconstructed vocal tracts of fossil Australopithecine and Neanderthaloid hominids. Vocal tract area functions that were directed towards making the best possible approximations to the human vowels /a/, /i/, and /u/, as well as certain consonantal configurations, were modeled by means of a computer program. The lack of these vowels in the phonetic repertoires of these creatures, who lack a pharyngeal region like that of adult Homo sapiens, may be concomitant with the absence of speech encoding and a consequent linguistic ability inferior to modern man.

Response of the Primary Auditory Neuron to Human Speech

A previous report [81st Meeting Acoust. Soc. Amer., J. Acoust. Soc. Amer. 50, 83(A) (1971)] documented that pulse occurrence histograms from primary auditory neurons of guinea pigs followed the time history of the bidirectional displacement patterns of the basilar membrane predicted by an electronic “analog cochlea” model. The basilar membrane describes a surface when stimulated by an auditory signal. This surface represents the point by point displacement of the basilar membrane along its length as a function of time. This paper presents data from many neurons distributed (on the basis of characteristic frequency) along the length of the basilar membrane. The data demonstrate that the temporal and spatial details of the complex surfaces of human speech sounds are preserved in the pulse occurrence histograms up to the temporal resolving power of our computer system (200 μsec). At low stimulus intensity, only those features that correspond to large displacements are seen in the pulse occurrence histogram; as stimulus intensity is progressively increased, features corresponding to smaller amplitude displacements progressively appear. There is not a linear relationship between magnitude of displacement and magnitude of neural response. Although the data collected to date have been analyzed on the basis of displacement patterns, we are unable to exclude velocity of the basilar membrane as the input to the primary neuron.

Phonetic Ability and Related Anatomy of the Newborn and Adult Human, Neanderthal Man, and the Chimpanzee

The sounds of human speech make human language a rapid medium of communication through a process of speech “encoding.” The presence of sounds like the vowels [a], [i], and [u] makes this process possible. The supralaryngeal vocal tracts of newborn Homo sapiens and chimpanzee are similar and resemble the reconstructed vocal tract of the fossil La Chapelle‐aux‐Saints Neanderthal man. Vocal tract area functions that were directed toward making best possible approximations to the human vowels [a], [i], and [u], as well as certain consonantal configurations, were modeled by means of a computer program. The lack of these vowels in the phonetic repertories of these creatures, who lack a supralaryngeal pharyngeal region like that of adult Homo sapiens, may be concomitant with the absence of speech encoding and a consequently linguistic ability inferior to modern man.

Language, name, and concept.

The experiment of teaching a young chimpanzee to use American sign language1 is an important advance on previous attempts to test the linguistic potential of primates. For the first time, a primate’s capacity for a language used by some humans has been clearly separated from his capacity for making the sounds of human speech. In the nature of things, this pioneer study has been made under special conditions, and (like any single study) cannot be assumed to be perfectly representative. Nevertheless, it does offer evidence of a new kind, in the light of which it is timely to reexamine the relation between human language and the signals that animals use or can learn to use.

Some Characteristics of the Human Speech Sounds

Some Characteristics of the Human Speech Sounds

Habituation in relation to state in the human neonate.

IN a polygraphic study it was found that newborn babies responded differentially to pure and to patterned tones of equal sound pressure1. Patterned (square-wave) tones were more potent stimuli for eliciting electromyographic responses than pure (sine-wave) tones and within each of these categories those tones with low frequency fundamentals elicited most responses. Square-wave tones with low frequency fundamentals possess certain structural similarities to human speech sounds. They were therefore categorized as “supernormal” stimuli because they elicited more responses than the voice itself, which in turn was more potent than any of the sine-wave tones.

Olivocochlear Bundle: Relationships to Signal Discrimination in Noise.

Monkeys, trained to discriminate between human speech sounds presented at 70 dB SPL in 2400-Hz low-pass noise of different intensities, were found significantly impaired in their performance following surgical section of the crossed OCB. There is absolutely no loss in the ability to discriminate between the signals in the absence of noise. The deficit is related to “perceptual” (as opposed to physical) signal-to-noise ratio: high intensity noise per se is insufficient to cause performance decrement if its passband provides inadequate masking of the speech stimuli (e.g., 2400 Hz high pass). The magnitude of the postoperative deficit is apparently related to the extent of destruction of the fibers of the OCB.

Vocabulary Statistics and Phonology: A Parallel

This state of affairs is altered abruptly if, from the fact of the distinctive property of the sounds of speech, the logical conclusion is drawn that it is just their symbolic values which must be made a subject of research as being linguistically the most essential feature, for the world behind the empirical sounds of human speech appears to be an ordered system which, through its fundamentally regular structure, is comparable to the grammatical values, so that between phonetics studied from this angle and grammar there no longer exists a fundamental difference.

Extant Problems in Analysis-Synthesis Telephony

Efficient voice communication implies transmission of the minimum information necessary to specify a speech event and to evoke an appropriate response. Human speakers generate information at rates which are much less than the capacity of conventional telephone channels. This disparity has motivated considerable research in analysis-synthesis techniques for speech transmission. One premise is common to most of the analysis-synthesis schemes; namely, the transmission system should be constrained so that the appropriate message ensemble contains only the sounds of human speech. One attempts, therefore, to build into the communication link as many as possible of the constraints characterizing the production and the perception of speech. Further, one hopes to manipulate the parameters of the constraints with as few independent, low information-rate signals as possible. This paper attempts to review briefly the progress which has been made with analysis-synthesis telephony, and endeavors to appraise the current status of the research. It undertakes to suggest how recent work in speech production may find application in transmission systems, and to point up some of the problems confronting further development. Finally, it considers briefly the potentialities of simulating speech systems with digital computers.

Vowel Measurements

In an paper addressed to linguists and phoneticians it were superfluous to dwell upon the importance of phonetics. All scholars interested in philological research or in modern language instruction must be aware that the teaching of living tongues is greatly improved by a knowledge of phonetics, and that without this science the satisfactory pursuit of comparative philology is impossible. Whatever be the system we adopt in the French and German courses of our colleges and schools, we must admit that pronunciation is an essential element; and the intelligent teaching of pronunciation demands an acquaintance with the physical action by which the sounds of human speech are created and modified. The American teacher, if he have exceptional advantages and an unusually delicate ear, may perhaps be able by mere imitation to acquire a correct foreign accent himself, but neither he nor the foreigner can ever, without a knowledge of phonetics, tell his pupils how to reproduce it. As for the science which we commonly call philology, it consists mainly of the study of sound changes; and the only solid foundation for such study is, obviously, a thorough mastery of the principles of sound-production.