Results of the noise assessments indicated levels that are damaging to the human auditory system. Such levels could be considered dangerous for kenneled dogs as well, particularly given the demonstrated hearing loss in dogs housed in the veterinary kennel for a prolonged period. Noise abatement strategies should be a standard part of kennel design and operation when such kennels are intended for long-term housing of dogs.
Previous investigators have shown that speech waves can undergo any one of a number of severe forms of distortion in low ambient noise levels without serious reduction of word articulation. There are well-known notable exceptions (e.g., center clipping). However, it is not enough to avoid these exceptional forms of distortion. In the study reported here it has been demonstrated that combinations of speech-wave distortions, which individually are quite innocuous with regard to word articulation, can be devastating in their combined effect, even in the absence of serious noise. Four types of speech-wave distortion were studied, individually and in combination, as follows: gross attenuation of high-frequency components, multiple echo, random amplitude modulation, and gross irregularity of response-frequency characteristic. Ambient noise was also a controlled environmental condition in some phases of the investigation. * This work was sponsored by the U.S. Air Force under Contract AF33(616)-2320. Paper delivered at 50th meeting of the Acoustical Society of America, December 16, 1955, at Providence, Rhode Island. • J.P. Egan et al., "The performance of communication equipment in noise," Harvard University Psycho-Acoustic Laboratory Report OSRD 901 (MHR-21) (1942).
The acoustic differences between whispered and normally phonated speech are large; yet whispered speech is still very discriminable. Since replacing a periodic voicing source with an aperiodic excitation does not significantly affect perception, there exists the possibility of a central processing stage to augment the normal peripheral processing. In the present experiments, the 16 CV syllables used by Miller and Nicely (1955) are whispered by three male and three female talkers. The data are used to collect confusion matrices from listeners who discriminate among 64 sample syllables from each talker. Data are also collected with stimuli involving normal and loud speech, in an attempt to determine what, if any, acoustic cues might discriminate between the consonants across stimulus conditions. The consonant confusions are obtained using a multitalker babble as a masker. Babble is used instead of white noise because it should equally mask all speech stimuli, whereas white noise may mask some stimuli, such as fricatives, more than others. Probabilities of consonant confusions across the voicing dimension for whispered speech will be presented.
Loud speech stimuli were collected from three males and three females saying the 16 CV syllables of Miller and Nicely (1955). Headphone sidetone was mixed with 80 dBA pink noise. Talkers were instructed to speak loud enough to hear their voices over the masker. This resulted in average speech levels of 100 dBA at 1 ft. Only the loud speech was recorded. The intratalker speech levels were controlled within 2 dB. Seven subjects listened to the loud speech at a ‘‘comfortable’’ level, in quiet and mixed with multitalker babble. Subjects averaged 82% correct in quiet and 53% in babble. There were no significant performance differences for male and female talkers. Fricatives accounted for most errors with errors across all phonetic dimensions in both quiet and babble. In babble, subjects correctly identified voiceless stops 61% of the time but correctly classified stimuli as voiceless stops (place errors only) 92% of the time. Also in babble, nasals and voiced stops were confused 15% of the time; these errors never occurred in quiet.
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