The Extended Speech Transmission Index: Predicting speech intelligibility in fluctuating noise and reverberant rooms

The Speech Transmission Index (STI) is used to predict speech intelligibility in noise and reverberant environments. However, measurements and predictions in fluctuating noises lead to inaccuracies. In the current paper, the Extended Speech Transmission Index (ESTI) is presented in order to deal with these shortcomings. Speech intelligibility in normally hearing subjects was measured using stationary and fluctuating maskers. These results served to optimize model parameters. Data from the literature were then used to verify the ESTI-model. Model outcomes were accurate for stationary maskers, maskers with artificial fluctuations, and maskers with real life non-speech modulations. Maskers with speech-like characteristics introduced systematic errors in the model outcomes, probably due to a combination of modulation masking, context effects, and informational masking

Extended speech intelligibility index for the prediction of the speech reception threshold in fluctuating noise

The extension to the speech intelligibility index (SII; ANSI S3.5-1997 (1997)) proposed by Rhebergen and Versfeld [Rhebergen, K.S., and Versfeld, N.J. (2005). J. Acoust. Soc. Am. 117(4), 2181-2192] is able to predict for normal-hearing listeners the speech intelligibility in both stationary and fluctuating noise maskers with reasonable accuracy. The extended SII model was validated with speech reception threshold (SRT) data from the literature. However, further validation is required and the present paper describes SRT experiments with nonstationary noise conditions that are critical to the extended model. From these data, it can be concluded that the extended SII model is able to predict the SRTs for the majority of conditions, but that predictions are better when the extended SII model includes a function to account for forward maskin

The dynamic range of speech, compression, and its effect on the speech reception threshold in stationary and interrupted noise

Changes in the speech reception threshold (SRT) after amplitude compression of speech or speech in noise may be due to changes in the dynamic range of the speech signal. However, current models set up to predict the speech intelligibility consider the dynamic range of speech to be fixed regardless of the type of compression. The present paper describes two experiments with normal-hearing subjects to examine the effect of the dynamic range on the SRT in stationary and interrupted noise after wide dynamic range compression. The dynamic range has been varied by compression or expansion of only the speech signal, leaving the masking noise unaltered, or by compression or expansion of the mixed speech-in-noise signal. The results show that compression affects the SRT, both in a positive or a negative direction, not only due to dynamic range but also due to distortion of the speech signa

Prediction of the intelligibility for speech in real-life background noises for subjects with normal hearing

OBJECTIVES: The speech reception threshold (SRT) traditionally is measured in stationary noise that has the long-term average speech spectrum of the target speech. However, in real life the instantaneous spectrum of the background noise is likely to be different from the stationary long-term average speech spectrum noise. To gain more insight into the effect of real-life background noises on speech intelligibility, the SRT of listeners with normal hearing was measured in a set of noises that varied in both the spectral and the temporal domain. This article investigates the ability of the extended speech intelligibility index (ESII), proposed by Rhebergen et al. to account for SRTs in these real-life background noises. DESIGN: SRTs in noise were measured in 12 subjects with normal hearing. Interfering noises consisted of a variety of real-life noises, selected from a database, and chosen on the basis of their spectrotemporal differences. Measured SRTs were converted to ESII values and compared. Ideally, at threshold, ESII values should be the same, because the ESII represents the amount of speech information available to the listener. RESULTS: SRTs ranged from -6 dB SNR (in stationary noise) to -21 dB SNR (in machine gun noise). Conversion to ESII values resulted in an average value of 0.34, with a standard deviation of 0.06. SRT predictions with the ESII model were better than those obtained with the conventional SII (ANSI 53.5-1997) model. In case of interfering speech, the ESII model predictions were poorer, because additional, nonenergetic (informational) masking is thought to occur. CONCLUSIONS: For the present set of masking noises, being representative for a variety of real-life noises, the ESII model of Rhebergen et al. is able to predict the SRTs of subjects with normal hearing with reasonable accuracy. It may be concluded that the ESII model can provide valuable predictions for the speech intelligibility in some everyday situation

Quantifying and modeling the acoustic effects of compression on speech in noise

In this presentation a method is proposed that is able to separate a speech signal out of a noise signal after processing of the signal through wide-dynamic-range compression (WDRC). This technique reconstructs the speech signal and noise signal sample by sample separately using the gain factor of the WDRC, and can be used to quantify the acoustic effects of WDRC in noise. It will be shown that this technique is more accurate than a frequently used inversion technique, because the method is not affected by phase shifts that introduce distortion products in the reconstructed speech signal. As a result, the acoustic effects of WDRC can be measured more accurately. In addition, this reconstruction method allows modeling the speech intelligibility after non-linear signal processing in the Speech Intelligibility Index. With the aid of Speech Reception Threshold data it will be shown that this approach can give a good account for most existing dat

Towards measuring the Speech Transmission Index in fluctuating noise: Accuracy and limitations

In the field of room acoustics, the modulation transfer function (MTF) can be used to predict speech intelligibility in stationary noise and reverberation and can be expressed in one single value: the Speech Transmission Index (STI). One drawback of the classical STI measurement method is that it is not validated for fluctuating background noise. As opposed to the classical measurement method, the MTF due to reverberation can also be calculated using an impulse response measurement. This indirect method presents an opportunity for STI measurements in fluctuating noise, and a first prerequisite is a reliable impulse response measurement. The conditions under which the impulse response can be measured with sufficient precision were investigated in the current study. Impulse response measurements were conducted using a sweep stimulus. Two experiments are discussed with variable absorption, different levels of stationary and fluctuating background noise, and different sweep levels. Additionally, simulations with different types of fluctuating noise were conducted in an attempt to extrapolate the experimental findings to other acoustical conditions. The experiments and simulations showed that a minimum impulse-to-noise ratio of +25 dB in fluctuating noise was needed. (C) 2017 Acoustical Society of Americ

Measuring Temporal Resolution (Release of Masking) with a Hughson-Westlake Up-Down Instead of a Bekesy-Tracking Procedure

Background: A temporal resolution test in addition to the pure-tone audiogram may be of great clinical interest because of its relevance in speech perception and expected relevance in hearing aid fitting. Larsby and Arlinger developed an appropriate clinical test, but this test uses a Bekesy-tracking procedure for estimating masked thresholds in stationary and interrupted noise to assess release of masking (RoM) for temporal resolution. Generally the Hughson-Westlake up-down procedure is used in the clinic to measure the pure-tone thresholds in quiet. A uniform approach will facilitate clinical application and might be appropriate for RoM measurements as well. Because there is no golden standard for measuring the RoM in the clinic, we examine in the present study the Hughson-Westlake up-down procedure to measure the RoM and compare the results with the Bekesy-tracking procedure. Purpose: The purpose of the current study was to examine the differences between a Bakesy-tracking procedure and the Hughson-Westlake up-down procedure for estimating masked thresholds in stationary and interrupted noise to assess RoM. Research Design: RoM is assessed in eight normal-hearing (NH) and ten hearing-impaired (HI) listeners through both methods. Results from both methods are compared with each other and with predicted thresholds from a model. Data Analysis: Wilcoxon signed-rank tests, paired t tests. Results: Some differences between the two methods were found. We used a model to quantify the results of the two measurement procedures. The results of the Hughson-Westlake procedure were clearly better in agreement with the model than the results of the Bekesy-tracking procedure. Furthermore, the Bekesy-tracking procedure showed more spread in the results of the NH listeners than the Hughson-Westlake procedure. Conclusions: The Hughson-Westlake procedure seems to be an applicable alternative for measuring RoM for temporal resolution in the clinical audiological practic

An audibility model of the headband trial with a bone conduction device in single-sided deaf subjects

Modelling the head-shadow effect compensation and speech recognition outcomes, we aimed to study the benefits of a bone conduction device (BCD) during the headband trial for single-sided deafened (SSD) subjects. This study is based on a database of individual patient measurements, fitting parameters, and acoustic BCD properties retrospectively measured on a skull simulator or from existing literature. The sensation levels of the Bone-Conduction and Air-Conduction sound paths were compared, modelling three spatial conditions with speech in quiet. We calculated the phoneme score using the Speech Intelligibility Index for the three conditions in quiet and seven in noise. Eighty-five SSD adults fitted with BCD during headband trial. According to our model, most subjects did not achieve a full head-shadow effect compensation with the signal at the BCD side and in front. The modelled speech recognition in the quiet conditions did not improve with the BCD on the headband. In noise, we found a slight improvement in some specific conditions and minimal worsening in others. Based on an audibility model, this study challenges the fundamentals of a BCD headband trial in SSD subjects. Patients should be counselled regarding the potential outcome and alternative approaches.</p

Cochlear implantation for tinnitus in adults with bilateral hearing loss: protocol of a randomised controlled trial

Introduction Tinnitus is the perception of sound without an external stimulus, often experienced as a ringing or buzzing sound. Subjective tinnitus is assumed to origin from changes in neural activity caused by reduced or lack of auditory input, for instance due to hearing loss. Since auditory deprivation is thought to be one of the causes of tinnitus, increasing the auditory input by cochlear implantation might be a possible treatment. In studies assessing cochlear implantation for patients with hearing loss, tinnitus relief was seen as a secondary outcome. Therefore, we will assess the effect of cochlear implantation in patients with primarily tinnitus complaints.Method and analysis In this randomised controlled trial starting in January 2021 at the ENT department of the UMC Utrecht (the Netherlands), patients with a primary complaint of tinnitus will be included. Fifty patients (Tinnitus Functional Index (TFI) &gt;32, Beck’s Depression Index &lt;19, pure tone average at 0.5, 1, 2 and 4 kHz: bilateral threshold between 50 and ≤75 dB) will be randomised towards cochlear implantation or no intervention. Primary outcome of the study is tinnitus burden as measured by the TFI. Outcomes of interest are tinnitus severity, hearing performances (tinnitus pitch and loudness, speech perception), quality of life, depression and patient-related changes. Outcomes will be evaluated prior to implantation and at 3 and 6 months after the surgery. The control group will receive questionnaires at 3 and 6 months after randomisation. We expect a significant difference between the cochlear implant recipients and the control group for tinnitus burden.Ethics and dissemination This research protocol was approved by the Institutional Review Board of the University Medical Center (UMC) Utrecht (NL70319.041.19, V5.0, January 2021). The trial results will be made accessible to the public in a peer-review journal.Trial registration number Trial registration number NL8693; Pre-results