The influence of stop consonants’ perceptual features on the Articulation Index model

Abstract

Studies on consonant perception under noise conditions typically describe the average consonant error as exponential in the Articulation Index (AI). While this AI formula nicely fits the average error over all consonants, it does not fit the error for any consonant at the utterance level. This study analyzes the error patterns of six stop consonants /p, t, k, b, d, g/ with four vowels (/α/, /ε/, /I/, /ae/), at the individual consonant (i.e., utterance) level. The findings include that the utterance error is essentially zero for signal to noise ratios (SNRs) at least -2 dB, for >78% of the stop consonant utterances. For these utterances, the error is essentially a step function in the SNR at the utterance's detection threshold. This binary error dependence is consistent with the audibility of a single binary defining acoustic feature, having zero error above the feature's detection threshold. Also 11% of the sounds have high error, defined as ≥ 20% for SNRs greater than or equal to -2 dB. A grand average across many such sounds, having a natural distribution in thresholds, results in the error being exponential in the AI measure, as observed. A detailed analysis of the variance from the AI error is provided along with a Bernoulli-trials analysis of the statistical significance.

Perception of voicing and place of articulation in labial and alveolar English stop consonants

“…The reported deviations from simple feature structure are broadly consistent with the feature interactions suggested by previous work on confusions induced by speechweighted noise (Phatak and Allen 2007;Singh and Allen 2012). Such deviations provide at least some support for the segment as basic perceptual unit (Nearey 1990;Norris et al 2000).…”

“…As mentioned above, a number of previous studies of speech in noise have focused on the perception of large sets of consonants, typically analyzing responses pooled across (sets of) listeners (Miller and Nicely 1955;Benkí 2003;Cutler et al 2004;Allen 2005;Phatak and Allen 2007;Singh and Allen 2012). By way of contrast, in the experiments described below, feature perception is analyzed for the smaller set of consonants - [p] The focus of the present work is restricted to place and voicing in this subset of English stop consonants in part so that the results are more or less directly com parable to similar results in previous studies with similarly narrow scope (e.g., Sawusch and Pisoni 1974;Oden and Massaro 1978), and in part because categories defined by the factorial combination of two levels on each of two dimensions maps directly onto the simplest full factorial GRT model (described in detail below).…”

“…While white noise seems to induce reasonably wellbehaved featurebased perceptual grouping (Miller and Nicely 1955;Allen 2005), speechweighted noise may induce more eclectic perceptual grouping (Phatak and Allen 2007). Noise maskers may also interact with tokenspecific acoustic properties of stimuli, influencing overall error rates and confusion patterns (Singh and Allen 2012).…”

Within-consonant perceptual differences in the hearing impaired ear

“…Thus the total number presentations of each consonant ranged from N ¼ 40 to 80 for each HI ear (total N ¼ 5-10 over 2 sessions  2 tokens  4 SNRs). The Vysochanskij-Petunin inequality (Vysochanskij and Petunin, 1980) was used to verify that the number of trials were sufficient to determine correct perception within a 95% confidence interval (see appendix of Singh and Allen, 2012).…”

“…To ensure that tokens were unambiguous and robust to noise, each token was selected based on a criteria of 3.1% error for a population of 16 NH listeners, calculated by combining results in quiet and at a À2 dB signal-to-noise ratio (SNR) (i.e., no more than 1 error over a total N ¼ 32, per token) (Phatak and Allen, 2007). Such tokens are representative of the LDC database; Singh and Allen (2012) shows, for the majority of tokens, a ceiling effect for NH listeners above À2 dB SNR. One token of =fA= (male talker, label m112) was damaged in the preparation of the tokens, thus it has not been included in this analysis.…”