Maureen Coughlin

Auditory measures of selective and divided attention in young and older adults using single-talker competition

In this study, two experiments were conducted on auditory selective and divided attention in which the listening task involved the identification of words in sentences spoken by one talker while a second talker produced a very similar competing sentence. Ten young normal-hearing (YNH) and 13 elderly hearing-impaired (EHI) listeners participated in each experiment. The type of attention cue used was the main difference between experiments. Across both experiments, several consistent trends were observed. First, in eight of the nine divided-attention tasks across both experiments, the EHI subjects performed significantly worse than the YNH subjects. By comparison, significant differences in performance between age groups were only observed on three of the nine selective-attention tasks. Finally, there were consistent individual differences in performance across both experiments. Correlational analyses performed on the data from the 13 older adults suggested that the individual differences in performance were associated with individual differences in memory (digit span). Among the elderly, differences in age or differences in hearing loss did not contribute to the individual differences observed in either experiment.

The relation between identification and discrimination of vowels in young and elderly listeners

This study examined both the identification and discrimination of vowels by three listener groups: elderly hearing-impaired, elderly normal-hearing, and young normal-hearing. Each hearing-impaired listener had a longstanding symmetrical, sloping, mild-to-moderate sensorineural hearing loss. Two signal levels [70 and 95 dB sound-pressure level (SPL)] were selected to assess the effects of audibility on both tasks. The stimuli were four vowels, /I,e, epsilon, ae/, synthesized for a female talker. Difference limens (DLs) were estimated for both F1 and F2 formants using adaptive tracking. Discrimination DLs for F1 formants were the same across groups and levels. Discrimination DLs for F2 showed that the best formant resolution was for the young normal-hearing group, the poorest was for the elderly normal-hearing group, and resolution for the elderly hearing-impaired group fell in between the other two at both signal levels. Only the elderly hearing-impaired group had DLs that were significantly poorer than those of the young listeners at the lower, 70 dB, level. In the identification task at both levels, young normal-hearing listeners demonstrated near-perfect performance (M = 95%), while both elderly groups were similar to one another and demonstrated lower performance (M = 71%). The results were examined using correlational analysis of the performance of the hearing-impaired subjects relative to that of the normal-hearing groups. The results suggest that both age and hearing impairment contribute to decreased vowel perception performance in elderly hearing-impaired persons.

Discrimination and identification of vowels by young, hearing-impaired adults

This study examined the effects of mild-to-moderate sensorineural hearing loss on vowel perception abilities of young, hearing-impaired (YHI) adults. Stimuli were presented at a low conversational level with a flat frequency response (approximately 60 dB SPL), and in two gain conditions: (a) high level gain with a flat frequency response (95 dB SPL), and (b) frequency-specific gain shaped according to each listeners hearing loss (designed to simulate the frequency response provided by a linear hearing aid to an input signal of 60 dB SPL). Listeners discriminated changes in the vowels /I e E inverted-v ae/ when F1 or F2 varied, and later categorized the vowels. YHI listeners performed better in the two gain conditions than in the conversational level condition. Performances in the two gain conditions were similar, suggesting that upward spread of masking was not seen at these signal levels for these tasks. Results were compared with those from a group of elderly, hearing-impaired (EHI) listeners, reported in Coughlin, Kewley-Port, and Humes [J. Acoust. Soc. Am. 104, 3597-3607 (1998)]. Comparisons revealed no significant differences between the EHI and YHI groups, suggesting that hearing impairment, not age, is the primary contributor to decreased vowel perception in these listeners.

Vowel perception by noise masked normal-hearing young adults.

This study examined vowel perception by young normal-hearing (YNH) adults, in various listening conditions designed to simulate mild-to-moderate sloping sensorineural hearing loss. YNH listeners were individually age- and gender-matched to young hearing-impaired (YHI) listeners tested in a previous study [Richie et al., J. Acoust. Soc. Am. 114, 2923-2933 (2003)]. YNH listeners were tested in three conditions designed to create equal audibility with the YHI listeners; a low signal level with and without a simulated hearing loss, and a high signal level with a simulated hearing loss. Listeners discriminated changes in synthetic vowel tokens /I e epsilon alpha ae/ when Fl or F2 varied in frequency. Comparison of YNH with YHI results failed to reveal significant differences between groups in terms of performance on vowel discrimination, in conditions of similar audibility by using both noise masking to elevate the hearing thresholds of the YNH and applying frequency-specific gain to the YHI listeners. Further, analysis of learning curves suggests that while the YHI listeners completed an average of 46% more test blocks than YNH listeners, the YHI achieved a level of discrimination similar to that of the YNH within the same number of blocks. Apparently, when age and gender are closely matched between young hearing-impaired and normal-hearing adults, performance on vowel tasks may be explained by audibility alone.

Aided speech recognition in single‐talker competition by elderly hearing‐impaired listeners

This study examined the speech‐identification performance in one‐talker interference conditions that increased in complexity while audibility was ensured over a wide bandwidth (200–4000 Hz). Factorial combinations of three independent variables were used to vary the amount of informational masking. These variables were: (1) competition playback direction (forward or reverse); (2) gender match between target and competition talkers (same or different); and (3) target talker uncertainty (one of three possible talkers from trial to trial). Four groups of listeners, two elderly hearing‐impaired groups differing in age (65–74 and 75–84 years) and two young normal‐hearing groups, were tested. One of the groups of young normal‐hearing listeners was tested under acoustically equivalent test conditions and one was tested under perceptually equivalent test conditions. The effect of each independent variable on speech‐identification performance and informational masking was generally consistent with expectations. Gr...

Better‐ear listening strategies for normal‐hearing and hearing‐impaired individuals

The current study was designed to examine how hearing‐impaired (HI) listeners use better‐ear listening. Better‐ear performance was initially assessed for normal‐hearing (NH) and HI participants using a connected‐speech recognition test at two signal‐to‐noise‐ratio (SNR) levels presented over insert earphones. Test conditions consisted of monaural, symmetric and asymmetric combinations of better and worse SNR conditions. SNRs were different for NH and HI groups. Stimuli were presented at each participants most comfortable level; to account for audibility with HI participants, stimuli were spectrally shaped based on audiometric data. A second experiment investigated the role of spatial information using recordings of the same stimuli presented in a sound‐dampened chamber at the same SNR differences, with the speech signal at 0° azimuth/elevation, and uncorrelated babble presented from eight speakers at the corners of the chamber. Listening strategies between NH and HI groups were similar across experiments...

Utilizing the auditory systems processing capabilities in the development of methods to auto‐steer signal processing strategies in hearing instruments

Hearing instruments have evolved in both the hardware and signal processing domains, providing more computational capabilities and sophisticated sound processing strategies. Static or adaptive methods are employed by these sound processing strategies to achieve a desired output. Due to the adaptive nature of some of these processing strategies and the continual increase in the number of parameters that can interact negatively with each other, there is a need to provide some method of global control over the parameter states. In addition, due to individual needs of the end user, parameter states in a hearing instrument may not satisfy the broad range of acoustic environments that a listener encounters, so identification of particular acoustic environment characteristics is also important. The purpose of this work is to introduce and discuss these problems and some of the current research efforts addressing environmental classification and global control of a hearing instrument’s parameter states. The scope of this discussion will be on strategies employed to meet the needs of the end user in reference to the acoustic environment they identify as having a negative impact on their auditory experience and the desired performance they expect from the hearing instrument in that environment.

The time course of learning during a vowel discrimination task by hearing‐impaired and masked normal‐hearing listeners

Vowel discrimination was compared between a group of young, well‐trained listeners with mild‐to‐moderate sensorineural hearing impairment (YHI), and a matched group of normal hearing, noise‐masked listeners (YNH). Unexpectedly, discrimination of F1 and F2 in the YHI listeners was equal to or better than that observed in YNH listeners in three conditions of similar audibility [Davis et al., J. Acoust. Soc. Am. 109, 2501 (2001)]. However, in the same time interval, the YHI subjects completed an average of 55% more blocks of testing than the YNH group. New analyses were undertaken to examine the time course of learning during the vowel discrimination task, to determine whether performance was affected by number of trials. Learning curves for a set of vowels in the F1 and F2 regions showed no significant differences between the YHI and YNH listeners. Thus while the YHI subjects completed more trials overall, they achieved a level of discrimination similar to that of their normal‐hearing peers within the same ...

Discrimination and identification of vowels in hearing‐impaired and masked normal‐hearing listeners

This study examined the effects of mild‐to‐moderate sloping sensorineural hearing loss on vowel discrimination and identification. Five young, hearing‐impaired (YHI) adults listened to vowel stimuli in three conditions: (a) at a conversational level with flat frequency response; and in two gain conditions, (b) at a high‐sound level with flat frequency response; and (c) with frequency shaped gain according to the subject’s hearing loss. Listeners discriminated changes in the synthetic vowels /I e e ae ʌ/ when F1 or F2 varied, and later identified the five vowels in a closed‐set task. The results indicated that neither gain condition restored performance to that of young, normal‐hearing listeners and that the potential upward spread of masking in condition (b) did not affect performance. Young, normal‐hearing (YNH) listeners were age matched to YHI subjects. Hearing thresholds for the YNH listener of each YHI–YNH pair were precisely matched to those of the YHI listener by masking with spectrally shaped noise...

The relation between identification and discrimination of vowels by young normal‐hearing and elderly hearing‐impaired listeners

Four young normal‐hearing (YNH) and four elderly hearing‐impaired subjects (EHI) with moderate sloping sensori‐neural hearing losses participated in vowel‐identification and formant‐discrimination tasks. To examine the relationship between vowel‐identification and formant‐discrimination abilities in conditions differing in audibility, signals were presented at two levels (70 and 95 dB SPL). Four mid‐vowels (/I/, /e/, /e/, and /ae/) were chosen as the target signals for both tasks. Identification performance for the YNH subjects was near ceiling performance. The EHI subjects averaged 80% for the 95 dB and 69% for the 70 dB SPL presentation level, although individual subject variability was high. Equivalent discrimination performance in the F1 region (ΔF threshold approximately 30 Hz) was observed for all four vowels, between groups and across levels. In the F2 region the EHI subjects’ thresholds were elevated compared to the YNH subjects at both levels, even when the formants appeared to be fully audible (a...