Acoustical analyses were carried out on a set of utterances produced by two male speakers talking in quiet and in 80, 90, and 100 dB SPL of masking noise. In addition to replicating previous studies demonstrating increases in amplitude, duration, and vocal pitch while talking in noise, these analyses also found reliable differences in the formant frequencies and short-term spectra of vowels. Perceptual experiments were also conducted to assess the intelligibility of utterances produced in quiet and in noise when they were presented at equal S/N ratios for identification. In each experiment, utterances originally produced in noise were found to be more intelligible than utterances produced in the quiet. The results of the acoustic analyses showed clear and consistent differences in the acoustic-phonetic characteristics of speech produced in quiet versus noisy environments. Moreover, these acoustic differences produced reliable effects on intelligibility. The findings are discussed in terms of: (1) the nature of the acoustic changes that take place when speakers produce speech under adverse conditions such as noise, psychological stress, or high cognitive load; (2) the role of training and feedback in controlling and modifying a talker's speech to improve performance of current speech recognizers; and (3) the development of robust algorithms for recognition of speech in noise.

The present investigation examined the effects of cognitive workload on speech production. Workload was manipulated by having talkers perform a compensatory visual tracking task while speaking test sentences of the form "Say hVd again." Acoustic measurements were made to compare utterances produced under workload with the same utterances produced in a control condition. In the workload condition, some talkers produced utterances with increased amplitude and amplitude variability, decreased spectral tilt and F0 variability and increased speaking rate. No changes in F1, F2, or F3 were observed across conditions for any of the talkers. These findings indicate both laryngeal and sublaryngeal adjustments in articulation, as well as modifications in the absolute timing of articulatory gestures. The results of a perceptual identification experiment paralleled the acoustic measurements. Small but significant advantages in intelligibility were observed for utterances produced under workload for talkers who showed robust changes in speech production. Changes in amplitude and amplitude variability for utterances produced under workload appeared to be the major factor controlling intelligibility. The results of the present investigation support the assumptions of Lindblom's ["Explaining phonetic variation: A sketch of the H&H theory," in Speech Production and Speech Modeling (Klewer Academic, The Netherlands, 1990)] H&H model: Talkers adapt their speech to suit the demands of the environment and these modifications are designed to maximize intelligibility.

Vervet monkeys routinely produce semantic alarm calls upon detection of various predators encountered in their natural environment. Two of these calls, snake and eagle alarms, were analyzed using digital signal processing techniques in order to identify potentially distinctive acoustic cues. Distinctive cues were sought in the periodicity of the source waveform associated with each call type, the probable vocal tract filtering functions, and in temporal patterning. Results were equivocal with respect to source periodicity, but a variety of distinguishing features were found in both supralaryngeal filtering and timing. These data provide a basis for psychoacoustic perceptual testing with vervets as subjects.

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In this report we consider the possibility that speech analysis techniques may be used to determine whether an individual was intoxicated at the time that a voice recording was made, and discuss an analysis of the speech produced by the captain of the Exxon Valdez recorded at several points around the time of the accident at Prince William Sound, Alaska. A review of previous research on the effects of alcohol and other effects on speech production suggests that it may be possible to attribute a certain, unique pattern of changes in speech to the influence of alcohol. However, the rate of occurrence of this pattern or the reliability of a decision based on observations such as these is not known. Acoustic-phonetic analysis of a small number of tokens of Captain Hazelwood's speech recorded before, during and after the accident revealed a number of changes in speech behavior which are similar to the pattern of changes observed in previous laboratorybased research on the effects of alcohol on speech production. We conclude with a discussion of the limitations in making inferences concerning the state of the speaker upon the basis of phonetic data and then discuss several possible explanations of the pattern of change found in the recordings of Captain Hazelwood.In this report, we briefly summarize previous research on the effects of alcohol and other environmental and emotional factors on speech production. We then discuss an analysis of the speech produced by the captain of the Exxon Valdez recorded at several times before, during, and after the accident at Prince William Sound. The tapes that we analyzed and information concerning the communications/recording equipment and the times of the recordings were provided to us by the staff of the National Transportation Safety Board (NTSB). The Problem of Unique SpecificationBefore discussing Captain Hazelwood's speech, we wish to place the present investigation within a general framework. The question which we are attempting to address in this report is whether it is possible to determine if an individual was intoxicated at a particular time based on acoustic analyses of voice recordings. This question hinges crucially on whether there are properties of speech which occur when a speaker (any speaker) is intoxicated and which do not occur in any other circumstance. We will call this the problem of unique specification.Keith Johnson, Department of Linguistics, UCLA, Los Angeles, CA 90024-1543 (USA)The analyses reported in this paper were carried out in connection with the National Transportation Safety Board (NTSB) investigation of the Exxon Valdez accident that occurred on March 24, 1989. This is a revised version of the report which the authors submitted to the NTSB in May 1990. We wish to acknowledge the comments and criticisms of Dr. Malcolm Brenner and our colleagues at Indiana University. NIH Public Access Author ManuscriptPhonetica. Author manuscript; available in PMC 2012 December 18.Published in final edited form as: Phonetica. 1990 ; 47(3-4): 215-237.$wa...