The effect of hearing aid dynamic range compression on speech intelligibility in a realistic virtual sound environment.

Measures of "aided" speech intelligibility (SI) for listeners wearing hearing aids (HAs) are commonly obtained using rather artificial acoustic stimuli and spatial configurations compared to those encountered in everyday complex listening scenarios. In the present study, the effect of hearing aid dynamic range compression (DRC) on SI was investigated in simulated real-world acoustic conditions. A spatialized version of the Danish Hearing In Noise Test was employed inside a loudspeaker-based virtual sound environment to present spatialized target speech in background noise consisting of either spatial recordings of two real-world sound scenarios or quadraphonic, artificial speech-shaped noise (SSN). Unaided performance was compared with results obtained with a basic HA simulator employing fast-acting DRC. Speech reception thresholds (SRTs) with and without DRC were found to be significantly higher in the conditions with real-world background noise than in the condition with artificial SSN. Improvements in SRTs caused by the HA were only significant in conditions with real-world background noise and were related to differences in the output signal-to-noise ratio of the HA signal processing between the real-world versus artificial conditions. The results may be valuable for the design, development, and evaluation of HA signal processing strategies in realistic, but controlled, acoustic settings.

Guided ecological momentary assessment in real and virtual sound environments.

Ecological momentary assessment (EMA) outcome measures can relate people's subjective auditory experience to their objective acoustical reality. While highly realistic, EMA data often contain considerable variability, such that it can be difficult to interpret the results with respect to differences in people's hearing ability. To address this challenge, a method for "guided" EMA is proposed and evaluated. Accompanied and instructed by a guide, normal-hearing participants carried out specific passive and active listening tasks inside a real-world public lunch scenario and answered EMA questionnaires related to aspects of spatial hearing, listening ability, quality, and effort. In situ speech and background noise levels were tracked, allowing the guided EMA task to be repeated inside two acoustically matched, loudspeaker-based laboratory environments: a 64-channel virtual sound environment (VSE) and a three-channel audiology clinic setup. Results showed that guided EMA provided consistent passive listening assessments across participants and conditions. During active listening, the clinic setup was found to be less challenging than the real-world and the VSE conditions. The proposed guided EMA approach may provide more focused real-world assessments and can be applied in realistic laboratory settings to aid the development of ecologically valid hearing testing.

Speech intelligibility in a realistic virtual sound environment.

In the present study, speech intelligibility was evaluated in realistic, controlled conditions. "Critical sound scenarios" were defined as acoustic scenes that hearing aid users considered important, difficult, and common through ecological momentary assessment. These sound scenarios were acquired in the real world using a spherical microphone array and reproduced inside a loudspeaker-based virtual sound environment (VSE) using Ambisonics. Speech reception thresholds (SRT) were measured for normal-hearing (NH) and hearing-impaired (HI) listeners, using sentences from the Danish hearing in noise test, spatially embedded in the acoustic background of an office meeting sound scenario. In addition, speech recognition scores (SRS) were obtained at a fixed signal-to-noise ratio (SNR) of -2.5 dB, corresponding to the median conversational SNR in the office meeting. SRTs measured in the realistic VSE-reproduced background were significantly higher for NH and HI listeners than those obtained with artificial noise presented over headphones, presumably due to an increased amount of modulation masking and a larger cognitive effort required to separate the target speech from the intelligible interferers in the realistic background. SRSs obtained at the fixed SNR in the realistic background could be used to relate the listeners' SI to the potential challenges they experience in the real world.

A method for realistic, conversational signal-to-noise ratio estimation.

The analysis of real-world conversational signal-to-noise ratios (SNRs) can provide insight into people's communicative strategies and difficulties and guide the development of hearing devices. However, measuring SNRs accurately is challenging in everyday recording conditions in which only a mixture of sound sources can be captured. This study introduces a method for accurate in situ SNR estimation where the speech signal of a target talker in natural conversation is captured by a cheek-mounted microphone, adjusted for free-field conditions and convolved with a measured impulse response to estimate its power at the receiving talker. A microphone near the receiver provides the noise-only component through voice activity detection. The method is applied to in situ recordings of conversations in two real-world sound scenarios. It is shown that the broadband speech level and SNR distributions are estimated more accurately by the proposed method compared to a typical single-channel method, especially in challenging, low-SNR environments. The application of the proposed two-channel method may render more realistic estimates of conversational SNRs and provide valuable input to hearing instrument processing strategies whose operating points are determined by accurate SNR estimates.