Effects of expansion algorithms on speech reception thresholds.

Area of Science:

• Audiology
• Hearing Aid Technology
• Signal Processing

Background:

• Expansion algorithms reduce microphone and environmental noise for hearing aid users.
• These algorithms may also affect the perception of low-level speech.
• Assessing the impact of different expansion types on speech reception is crucial.

Purpose of the Study:

• To evaluate the effect of single-channel and multiple-channel expansion algorithms on speech reception thresholds (SRT).
• To compare the performance of these algorithms with and without automatic dynamic range optimization (ADRO) processing in hearing aids.
• To determine if hearing loss severity correlates with the benefits of expansion algorithms.

Main Methods:

• Ten hearing-impaired listeners participated, wearing hearing aids with ADRO processing.
• Two expansion algorithms were tested: single-channel (suppressing sounds below 45 dB A) and multiple-channel (suppressing sounds below 45 or 55 dB SPL).
• Speech reception thresholds in quiet were measured using the Hearing in Noise Test (HINT).

Main Results:

• Mean HINT SRTs in quiet were 39.4 dB A (no expansion), 40.7 dB A (single-channel), 40.6 dB A (multi-channel at 45 dB SPL), and 41.8 dB A (multi-channel at 55 dB SPL).
• A statistically significant difference was found only between no expansion and multi-channel expansion at a 55 dB SPL threshold.
• No correlation was observed between individual SRT changes and pure-tone average hearing loss.

Conclusions:

• Multi-channel expansion at 55 dB SPL significantly improved SRT, suggesting its benefit for specific hearing profiles.
• The study questions the sole reliance on hearing thresholds for prescribing expansion algorithms.
• Alternative rationales for applying expansion algorithms in hearing aid fitting should be considered.