Cochlear implant users' spectral ripple resolution

Abstract

This study revisits the issue of the spectral ripple resolution abilities of cochlear implant (CI) users. The spectral ripple resolution of recently implanted CI recipients (implanted during the last 10 years) were compared to those of CI recipients implanted 15 to 20 years ago, as well as those of normal-hearing and hearing-impaired listeners from previously published data from Henry, Turner, and Behrens [J. Acoust. Soc. Am. 118, 1111-1121 (2005)]. More recently, implanted CI recipients showed significantly better spectral ripple resolution. There is no significant difference in spectral ripple resolution for these recently implanted subjects compared to hearing-impaired (acoustic) listeners. The more recently implanted CI users had significantly better pre-operative speech perception than previously reported CI users. These better pre-operative speech perception scores in CI users from the current study may be related to better performance on the spectral ripple discrimination task; however, other possible factors such as improvements in internal and external devices cannot be excluded.

FIG. 1.

Comparison of spectral ripple thresholds between cochlear implant subjects in the Henry et al. (2005) and the current studies. This box-and-whisker plot shows results from Henry et al. (2005) in the left panel and results from the current study in the right panel. The boxes extend from the 25th to 75th percentiles and the whiskers show data ranged from the 10th to 90th percentiles. Within the box, the thin solid line shows the median and the thick solid line show the mean spectral ripple thresholds of each group. Individual dots are outliers; scores are outside of 10th and 90th percentiles.

FIG. 2.

The relationship between spectral ripple discrimination thresholds and consonant recognition across normal hearing listeners (NH), hearing impaired (HI) listeners, and cochlear implant (CI) users. Closed circles indicate CI subjects' data from Henry et al. (2005). Open circles indicate CI subjects' data from the current study. Closed triangles indicate HI data and open triangles indicate NH data, both from Henry et al. (2005).

FIG. 3.

The relationship between spectral ripple discrimination thresholds and consonant recognition in CI users alone. Closed circles indicate CI subjects' data from Henry et al. (2005). Open circles indicate CI subjects' data from the current study.

FIG. 4.

The relationship between spectral ripple discrimination thresholds and speech recognition thresholds in two-talker speech maskers in CI users. Closed circles indicate CI subjects' data from Henry et al. (2005), and open circles indicate CI subjects' data from the current study.

FIG. 5.

Audiograms obtained preoperatively for all CI subjects in the two studies. (a) The audiograms of the subjects who participated in the Henry et al. (2005) study. (b) The audiograms of the current study. The thick grey line shows the mean threshold for each frequency for all subjects in each group.