Electromyographic responses of lower leg muscles to upward toe tilts as a function of age.

EMGs were recorded from the gastrocnemius and anterior tibialis muscles of 77 adult subjects in response to perturbation of stance by upward toe tilts. Subjects aged 22-88 y were initially grouped in seven decades (20s-80s). Each presented a history free of ear disease, eye disease not correctable by lenses, neurological disease, and persistent difficulty with balance or dizziness. All demonstrated functionally normal balance for their age on routine dynamic posturography. EMG recordings yielded onset and offset latencies, durations, and integrated amplitudes of the short and medium latency responses of the gastrocnemius and the long latency responses of the anterior tibialis. Analysis of the data revealed statistically significant left-right differences in amplitude of response and statistically significant height, gender, and age effects. Procedural issues were discussed; data were summarized for normative purposes; and suggestions were made for dealing with statistically significant differences in a clinical environment.

Magnitude estimation of degraded speech quality by normal- and impaired-hearing listeners.

Speech quality magnitude estimates (SQME's) were obtained from 12 sensorineurally impaired-hearing listeners on connected speech samples degraded by changing low-pass filter cutoff frequency, high-pass filter cutoff frequency, or percent total harmonic distortion (THD) by linear rectification. Log SQME's varied linearly with log bandwidth for filtered signals and with log percent undegraded (100-% THD) for linearly rectified signals. Significant variations were found among the slopes of the log-log functions for degradation modes and group-by-degradation mode interactions. Slope differences appeared to represent differential sensitivity of the listeners to changes in mode and degree of degradation. The findings are sufficiently encouraging to suggest that direct scaling procedures be employed in future studies of the evaluation of communication systems and the perception of complex signals.