The Self-Assessed Békesy Procedure: Validation of a Method to Measure Intelligibility of Connected Discourse

Abstract

In clinical practice and research, speech intelligibility is generally measured by instructing the participant to recall sentences. Although this is a reliable and highly repeatable measure, it cannot be used to measure intelligibility of connected discourse. Therefore, we developed a new method, the self-assessed Békesy procedure, which is an adaptive procedure that uses intelligibility ratings to converge to a person’s speech reception threshold. In this study, we describe the new procedure and the validation in young, normal-hearing listeners. First, we compared the results on the self-assessed Békesy procedure to a recall procedure for standardized sentences. Next, we evaluated the inter- and intrasubject variability of our procedure. Furthermore, we compared the thresholds for sentences in three masker types between the self-assessed Békesy and a recall procedure to verify if these procedures resulted in similar conclusions. Finally, we compared the thresholds for two types of sentences and commercial recordings of stories. In general, the self-assessed Békesy procedure is shown to be a valid and reliable procedure as similar thresholds (difference < 1 dB) and test–retest reliability (< 1.5 dB) were observed compared with standard speech audiometry tests. In addition, the time efficiency and similar differences between maskers to a recall procedure support the potential of this procedure to be implemented in research. Finally, significant differences between the thresholds of sentences and connected discourse materials were found, indicating the importance of controlling for differences in intelligibility when presenting these materials at the same signal-to-noise ratios or when comparing studies.

The effect of stimulus choice on an EEG-based objective measure of speech intelligibility

“…Finally, speech intelligibility for both stimuli was measured in a different way: rating (natural story) versus recall (Matrix sentences). Similar to the very small and insignificant difference of 0.5 dB between rate and recall of Matrix sentences reported by Decruy et al (2018), we did not find any statistical difference either between both measuring methods applied on the same Matrix sentences.…”

Evidence for enhanced neural tracking of the speech envelope underlying age-related speech-in-noise difficulties

“…Following the matrix sentence test, we administered an adapted version of the self-assessed Békesy procedure (Decruy et al 2018) to create equivalent speech understanding levels for the story used during the EEG experiment. During this procedure, participants were provided with a scale from 0 to 100% to rate their speech understanding.…”

“…To ensure comparable understanding levels for matrix and story, as well as to avoid the confounds of rating biases, we used the difference in SRT between matrix and story on the self-assessed Békesy procedure (Decruy et al 2018), further described as "Békesy procedure," as an adjustment value. Consequently, the story-adjusted SRT per participant was calculated by subtracting this adjustment value from the SRT on the matrix test ( Fig.…”

“…The story that we used in this study is "De Wilde Zwanen" by Hans Christian Andersen, narrated by a female, Flemish talker, and was 28 min long. The story was set to the same root mean square level and spectrum as the matrix sentences, and silences were shortened to a maximum duration of 200 ms based on the results of a previous study (Decruy et al 2018).…”

Prof. dr. nob. Georg von Békésy, Nobel Laureate

“…The Békésy tracking procedure is shown to be a valid andreliable even in recent investigations when modern information, computer and microelectronic technology is available and applied (see e.g. [10][11][12]). His valuable work is summarized in couple of works in the last decade [13], and the special issue was edited for the honor of 50 th anniversary of the award of the Nobel Prize to him [14].…”