Memory for language in deaf adults and children

Preferred listening levels of personal listening devices in young teenagers: self reports and physical measurements

OBJECTIVE

To assess the potential risk of hearing loss to young listeners, due to the use of personal listening devices (PLDs).

DESIGN

The study included two parts: (1) A self-report questionnaire on music listening habits, and (2) Physical measurements of preferred listening levels, in quiet and in everyday background noise.

STUDY SAMPLE

Young teenagers aged 13 to 17 years. Part 1 included 289 participants with mean age of 14 years. Part 2 included 11 and 74 participants (2A and 2B) with a mean age of 15 years. Eleven listened to PLDs in quiet conditions (2A) and 74 in everyday background noise (2B).

RESULTS

Questionnaire main findings indicated that most of the participants reported high or very high volume settings and demonstrated low awareness towards loud music listening consequences. Physical measurements corrected for diffuse field indicated mean preferred listening levels of: 82 (SD = 9) dBA in quiet, and 89 (SD = 9) dBA in the presence of background noise. The potential risk to hearing of PLDs users was calculated using the 8 hour equivalent level.

CONCLUSION

More than 25% of the participants in the noisy condition were found to be at risk according to occupational damage risk criteria NIOSH, 1998.

Chinese deaf adolescents' free recall of taxonomic, slot-filler, and thematic categories

Four experiments were conducted to show that deaf adolescents tended to process information in different ways from hearing adolescents. Memorizing items sequentially shown on computer screens under the control of their articulators' movements, deaf adolescents tended to treat items that cohered as taxonomic, thematic, or slot-filler categories as isolated pieces of information. Having to perceive information by means of sign language, however, their achievements were not worse than those of hearing adolescents anymore, no matter whether the stimuli were presented as words or pictures. They could not only utilize categories relations to help memorize categories exemplars but were relatively better aware of slot-filler or thematic than taxonomic relations as well, suggesting that they had a relatively delayed development of taxonomic category representations in comparison with hearing adolescents.

Changes of Hair Cell Stereocilia and Threshold Shift after Acoustic Trauma in Guinea Pigs: Comparison between Inner and Outer Hair Cells

The vulnerability of inner hair cells (IHCs) and outer hair cells (OHCs) to acoustic overstimulation is still controversially discussed. The present study was undertaken to investigate the vulnerability of IHCs and OHCs and the relation between chronological changes of auditory threshold shifts and stereocilia damages on IHCs and OHCs in guinea pigs after moderate acoustic trauma, caused by a single continuous exposure to pink noise (20 Hz to 20 kHz) of around 106 +/- 2 dB SPL for 44 h. Stereocilia changes and threshold shifts of auditory brainstem responses (ABR) were assessed at regular intervals after noise exposure for 9 weeks. Scanning electron microscopy demonstrated the morphological changes of stereocilia as early as 1 day after noise exposure. The morphological changes included fused, bent, collapsed, and even missing stereocilia. These damages were more prominent on IHCs than on OHCs. The shift of ABR threshold was not parallel to the chronological change of the stereocilia on IHCs as well as OHCs. The elevation of the ABR threshold (40-60 dB SPL) was greatest on the 1st day after noise exposure, whereas the stereocilia showed the most damage 7 days after noise exposure. Combined with the results from previous studies, we conclude that moderate-level (around 105-110 dB) noise tends to induce more damage to the stereocilia of IHCs than of OHCs. Other damage (e.g., metabolic disturbance) than morphological damage of hair cell stereocilia may contribute partially to the hearing threshold shift induced by moderate acoustic overstimulation.