Effect of Compression, Digital Noise Reduction and Directionality on Envelope Difference Index, Log-Likelihood Ratio and Perceived Quality

Abstract

The aim of the present study was to evaluate the use of the envelope difference index (EDI) and log-likelihood ratio (LLR) to quantify the independent and interactive effects of wide dynamic range compression, digital noise reduction and directionality, and to carry out self-rated quality measures. A recorded sentence embedded in speech spectrum noise at +5 dB signal to noise ratio was presented to a four channel digital hearing aid and the output was recorded with different combinations of algorithms at 30, 45 and 70 dB HL levels of presentation through a 2 cc coupler. EDI and LLR were obtained in comparison with the original signal using MATLAB software. In addition, thirty participants with normal hearing sensitivity rated the output on the loudness and clarity parameters of quality. The results revealed that the temporal changes happening at the output is independent of the number of algorithms activated together in a hearing aid. However, at a higher level of presentation, temporal cues are better preserved if all of these algorithms are deactivated. The spectral components speech tend to get affected by the presentation level. The results also indicate the importance of quality rating as this helps in considering whether the spectral and/or temporal deviations created in the hearing aid are desirable or not.

Effect of Digital Noise Reduction and Directionality Algorithms in Hearing Aids on Temporal Envelope Distortion and Speech Recognition

“…This could be because of the way that noise reduction strategies work -they increase the temporal envelope modulation depth in the process of cutting down noise [16], which results in higher EDI. However, these findings go against the results of the study by Geetha and Manjula [19]. The difference might be due to a difference in stimulus presentation: in the current study, the sources of speech and noise were spatially separate (meaning that, as the literature demonstrates, directionality could work more effectively [28]), whereas in the earlier study the speech and noise emanated from the same source.…”

“…A study by Geetha and Manjula [19] has quantified the acoustic changes induced by compression, DNR, and directionality -in isolation and in combination -using EDI and measured the quality ratings. The authors recorded the output of the hearing aid in a 2 cc coupler and processed it to obtain an EDI.…”

“…In earlier studies, outputs of the hearing aid have been recorded using a 2 cc coupler [19], ear simulator [21], and real ear measurement [20]. The use of real ear measurement was considered a good strategy and was argued to give more realistic outcomes.…”

Assessment of the Clinical Utility of the Sentence Identification Test in Kannada for Adults

“…In another study in 2019, the same authors used the same sentence lists to evaluate the correlation between temporal integration and temporal envelope perception in noise [36]. The sentences have also been used to study the effect of the number of talkers in background speech babble on acceptable noise levels [37] and the effect of compression, digital noise reduction, and directionality on envelope difference index, log-likelihood ratio, and perceived quality [38].…”

Effect of Varied Gradation Levels of Noise Reduction Algorithm on Speech Perception through Acoustical and Perceptual Measures

“…The minimum NR gradation had the least effect on the noise, i.e., NR 'on' at minimum gradation was almost equivalent to NR 'off' position across all the types of noise. Geetha and Manjula [14] suggested that compression, DNR, and directionality are similar in terms of temporal changes that they introduce. Hence the results of EDI with manipulating the compression parameter may be utilized to compare with the EDI results while manipulating the NR algorithm.…”