Abstract
In this paper, the effects of intensifying useful frequency and time regions (target frequency and time ranges) and the removal of detrimental frequency and time regions (conflicting frequency and time ranges) for consonant enhancement were determined. Thirteen normal-hearing (NH) listeners participated in two experiments. In the first experiment, the target and conflicting frequency and time ranges for each consonant were identified under a quiet, dichotic listening condition by analyzing consonant confusion matrices. The target frequency range was defined as the frequency range that provided the highest performance and was decreased 40% from the peak performance from both high-pass filtering (HPF) and low-pass filtering (LPF) schemes. The conflicting frequency range was defined as the frequency range that yielded the peak errors of the most confused consonants and was 20% less than the peak error from both filtering schemes. The target time range was defined as a consonant segment that provided the highest performance and was decreased 40% from that peak performance when the duration of the consonant was systematically truncated from the onset. The conflicting time ranges were defined on the coincided target time range because, if they temporarily coincide, the conflicting frequency ranges would be the most detrimental factor affecting the target frequency ranges. In the second experiment, consonant recognition was binaurally measured in noise under three signal processing conditions: unprocessed, intensified target ranges by a 6-dB gain (target), and combined intensified target and removed conflicting ranges (target-conflicting). The results showed that consonant recognition improved significantly with the target condition but greatly deteriorated with a target-conflicting condition. The target condition helped transmit voicing and manner cues while the target-conflicting condition limited the transmission of these cues. Confusion analyses showed that the effect of the signal processing on consonant improvement was consonant-specific: the unprocessed condition was the best for /da, pa, ma, sa/; the target condition was the best for /ga, fa, va, za, ʒa/; and the target-conflicting condition was the best for /na, ʃa/. Perception of /ba, ta, ka/ was independent of the signal processing. The results suggest that enhancing the target ranges is an efficient way to improve consonant recognition while the removal of conflicting ranges negatively impacts consonant recognition.
Highlights
Consonant recognition depends on the listener’s ability to discriminate details of spectral and temporal acoustic cues such as voicing, an onset of the noise burst, and spectral and temporal transitions (Miller and Nicely, 1955; Stevens and Klatt, 1974; Stevens and Blumstein, 1978; Blumstein and Stevens, 1979, 1980)
Our results showed that the target and conflicting ranges are highly consonant-specific (Figures 2, 3)
The mean data obtained in this study were comparable with Li et al.’s (2010,2012) data (2010, 2012); this study data showed that the target and conflicting ranges were highly listener specific (Table 1)
Summary
Consonant recognition depends on the listener’s ability to discriminate details of spectral and temporal acoustic cues such as voicing, an onset of the noise burst, and spectral and temporal transitions (Miller and Nicely, 1955; Stevens and Klatt, 1974; Stevens and Blumstein, 1978; Blumstein and Stevens, 1979, 1980). Other studies used naturally produced consonants and identified the spectral and temporal cues for recognition (Soli, 1981; Baum and Blumstein, 1987; Behrens and Blumstein, 1988; Jongman et al, 2000). Through the analysis of confusion matrices, they were able to identify frequency and time ranges for each consonant, which resulted in a significant positive change in recognition and labeled them as “target frequency and time ranges.”. They noticed specific frequency and time ranges that produced a significant negative change in recognition called “conflicting frequency and time ranges.”. In this article, “conflicting” frequency and time ranges were defined as the ranges that generate more consonant confusion than enhancement
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