Improving Speech Intelligibility in Fluctuating Background Interference. Abstract: The goal of this research was to develop a signal-processing technique to improve speech intelligibility for hearing-impaired (HI) listeners in fluctuating background interference. Typically, the masking release (MR; i.e., better performance in a fluctuating compared to a continuous noise background) experienced by normal-hearing (NH) listeners is reduced or absent in hearing-impaired (HI) listeners for aided unprocessed speech materials. Recently, greater MR has been observed for various types of speech signals whose processing reduces or removes signal amplitude variations. The work reported here was concerned with implementing a method of signal processing to reduce variations in signal amplitude (thus leading to improved speech intelligibility in fluctuating interference) without suffering a loss in intelligibility in continuous background noise. The signal-processing technique described here was designed to increase the audibility of the lower-energy intervals of a speech-plus-noise signal through normalization of the short-term energy to match that of the long-term average energy. The technique simply compares short-term and long-term estimates of signal energy, increases the level of short-term segments whose energy is below the average signal energy, and normalizes the overall energy of the processed signal to be equivalent to that of the original long-term estimate. The method operates blindly on a speech-plus-noise signal without the need for segmentation, operates on relative levels of the speech and interference, and does not require a reference signal. Consonant-identification tests were conducted on NH and HI listeners to compare performance on unprocessed speech with that of speech processed with the energy-normalization technique. Performance was measured in backgrounds of continuous and fluctuating noises (including square-wave and sinusoidally modulated noises as well as those derived from speech envelopes). For both NH and HI listeners, similar scores were obtained for processed and unprocessed speech materials in quiet and continuous-noise backgrounds. For HI listeners, superior performance was obtained for the processed speech in some fluctuating background noises while NH listeners performed similarly in both types of speech. These results support the conclusion that greater MR for HI listeners may be related to decreased amplitude variation and increased audibility of the speech during gaps in the noise for energy-normalized signals.