Speaking Clearly for the Hard of Hearing IV: Further Studies of the Role of Speaking Rate

Abstract

The contribution of reduced speaking rate to the intelligibility of “clear” speech (Picheny, Durlach, & Braida, 1985) was evaluated by adjusting the durations of speech segments (a) via nonuniform signal time-scaling, (b) by deleting and inserting pauses, and (c) by eliciting materials from a professional speaker at a wide range of speaking rates. Key words in clearly spoken nonsense sentences were substantially more intelligible than those spoken conversationally (15 points) when presented in quiet for listeners with sensorineural impairments and when presented in a noise background to listeners with normal hearing. Repeated presentation of conversational materials also improved scores (6 points). However, degradations introduced by segment-by-segment time-scaling rendered this time-scaling technique problematic as a means of converting speaking styles. Scores for key words excised from these materials and presented in isolation generally exhibited the same trends as in sentence contexts. Manipulation of pause structure reduced scores both when additional pauses were introduced into conversational sentences and when pauses were deleted from clear sentences. Key-word scores for materials produced by a professional talker were inversely correlated with speaking rate, but conversational rate scores did not approach those of clear speech for other talkers. In all experiments, listeners with normal hearing exposed to flat-spectrum background noise performed similarly to listeners with hearing loss.

Temporal organization of English clear and conversational speech

“…The data provided strong evidence that talkers successfully maintained clear speech articulatory modifications across longer stretches of speech such that intelligibility was increased in all portions of the paragraphs. Previous clear speech research largely focused on intelligibility of isolated vowels, words, and short sentences ͑Picheny et Payton et al, 1994;Uchanski et al, 1996;Bradlow and Bent, 2002;Bradlow et al, 2003;Ferguson, 2004;Ferguson and Kewley-Port, 2002͒. The current results expand on these findings by demonstrating that clear speech modifications can increase the intelligibility of longer and more complex utterances.…”

“…Previous work on English clear speech production and perception has established that naturally produced clear speech enhances intelligibility for various listener populations including adults with normal or impaired hearing ͑Picheny et Payton et al, 1994;Uchanski et al, 1996;Ferguson, 2004;Ferguson and Kewley-Port, 2002;Bradlow, 2005͒, elderly adults ͑Schum, 1996;Helfer, 1998͒, both native and non-native listeners of the target language ͑Bradlow and Bent, 2002;Bradlow and Alexander, 2007;Smiljanic and Bradlow, 2007͒, and children with and without learning impairments ͑Bradlow et al, 2003͒. Acoustic comparisons of conversational and clear speech in English have shown that clear speech modifications typically involve enhancement of the overall acoustic salience of the speech signal by means of a decreased speaking rate, longer and more frequent pauses, an expanded pitch range, greater sound pressure levels, more salient stop releases, greater obstruent intensity, increased energy in the 1000-3000 Hz range of long-term spectra, and increased modulation depth of low frequency modulations of the intensity envelope ͑Picheny et Bradlow et al, 2003;Liu et al, 2004;Krause and Braida, 2004;Smiljanic and Bradlow, 2005͒.…”

Effects of talker, rate, and amplitude variation on recognition memory for spoken words

“…Rate variability within a given speaker is not achieved by a constant "stretching" or "shrinking" of the acoustic waveform in the temporal domain. Rather, certain acoustic segments are more dramatically reduced in duration than others when overall speaking rate is increased, and various other acoustic/phonetic changes (e.g., vowel reduction) occur in response to changes in speaking rate (see, e.g., Klatt, 1973Klatt, , 1976Lehiste, 1972;Picheny, Durlach, & Braida, 1986Port, 1981;Uchanski, Choi, Braida, Reed, & Durlach, 1996). Thus, an increase or decrease in speaking rate is clearly a dynamic, multidimensional transformation of the speech signal.…”

Intelligibility and Acoustic Characteristics of Clear and Conversational Speech in Telugu (A South Indian Dravidian Language)

“…Acoustic comparisons of conversational and clear speech in English have shown that clear speech modifications typically involve enhancement of the overall acoustic salience of the speech signal by means of a decreased speaking rate, longer and more frequent pauses, an expanded pitch range, greater sound pressure levels, more salient stop releases, greater obstruent intensity, increased energy in the 1000-3000 Hz range of long-term spectra, and increased modulation depth of low frequency modulations of the intensity envelope [3,12,14,18,19,26,28].…”