Speech Perception Benefit

Overview

We quantify the expected improvement in speech intelligibility for each device/fit combination via acoustic measurement. For all recordings, we compute the Hearing Aid Speech Perception Index v2 (HASPIv2[14]). We chose this metric because it models the impaired auditory system and predicts intelligibility for a wide range of acoustic environments.

Computation

We compute HASPIv2 using the N3 audiogram (Table 1) and RAU-transform[15] the output. We average across both ears and compute the difference between unaided and aided recordings:

\Delta\text{HASPIv2} = \text{HASPIv2}_{\text{aided}} - \text{HASPIv2}_{\text{unaided}}

Positive values indicate the hearing aid improved speech intelligibility; negative values indicate degradation.

Quiet/Moderate vs. Loud Environments

We report $\Delta$ HASPIv2 separately for two environment categories:

Sub-metric	Environment Criterion
Speech Perception Benefit (Quiet/Moderate, 5 background)	Background level < 70 dB SPL
Speech Perception Benefit (Loud, 7 background)	Background level > 70 dB SPL

For each category, we average the $\Delta$ HASPIv2 score across all qualifying acoustic scenes.

Mapping to 0--5 Scale

The resulting values are mapped to our 5-point scale via linear scaling.

A ΔHASPIv2 of 0 (no benefit relative to the open ear) maps to 0 on our scale, with increasing benefit scaled linearly up to 5.