Effect of Energy Equalization on the Intelligibility of Speech in Fluctuating Background Interference for Listeners With Hearing Impairment

Abstract

The masking release (MR; i.e., better speech recognition in fluctuating compared with continuous noise backgrounds) that is evident for listeners with normal hearing (NH) is generally reduced or absent for listeners with sensorineural hearing impairment (HI). In this study, a real-time signal-processing technique was developed to improve MR in listeners with HI and offer insight into the mechanisms influencing the size of MR. This technique compares short-term and long-term estimates of energy, increases the level of short-term segments whose energy is below the average energy, and normalizes the overall energy of the processed signal to be equivalent to that of the original long-term estimate. This signal-processing algorithm was used to create two types of energy-equalized (EEQ) signals: EEQ1, which operated on the wideband speech plus noise signal, and EEQ4, which operated independently on each of four bands with equal logarithmic width. Consonant identification was tested in backgrounds of continuous and various types of fluctuating speech-shaped Gaussian noise including those with both regularly and irregularly spaced temporal fluctuations. Listeners with HI achieved similar scores for EEQ and the original (unprocessed) stimuli in continuous-noise backgrounds, while superior performance was obtained for the EEQ signals in fluctuating background noises that had regular temporal gaps but not for those with irregularly spaced fluctuations. Thus, in noise backgrounds with regularly spaced temporal fluctuations, the energy-normalized signals led to larger values of MR and higher intelligibility than obtained with unprocessed signals.

The fluctuating masker benefit for normal-hearing and hearing-impaired listeners with equal audibility at a fixed signal-to-noise ratio

“…Although Phatak and Grant (2012) found that linear prescriptive gain cannot restore audibility for low-level consonant information, several researchers have investigated how nonlinear compression schemes can amplify low-level target speech occurring in the dips of a fluctuating masker to improve performance for HI listeners. For example, Desloge et al (2017) andD'Aquila et al (2017) tested an algorithm that selectively amplifies short, low-level portions of a combined speech and noise signal, and found that the algorithm improved performance for maskers containing regular temporal fluctuations. A standard hearing-aid fast-compression algorithm might also improve speech understanding in a fluctuating background (Lunner and Sundewall-Thor en, 2007), especially at low SNRs (Naylor and Johannesson, 2009), although Stone and Moore (2008) cautioned that such an approach could introduce distortion in a speech-on-speech masking situation.…”

Binaural consequences of speech envelope enhancement

“…In this case the goal was not to manipulate the existing modulations in speech but to exploit slower fluctuations in signal-to-noise ratio (SNR). By boosting the intensity of low energy portions of the signal, which tend to be speech, they showed improved intelligibility for a group of listeners with hearing loss [see also D'Aquila et al (2017) and Goldsworthy et al (2022) ]. It is worth noting that the non-linear compression that is present in nearly all modern hearing aids acts as an envelope compressor, though compression is typically applied within frequency bands and with a variety of considerations (such as correcting for loudness recruitment) in mind ( Dillon, 2012 ).…”