gms | German Medical Science

Introduction: The benefit of hearing aids is often evaluated by objective speech intelligibility tests during the fitting procedure. These tests are conducted in the laboratory or in a sound-insulated room either in quiet or in noise. The hearing aid benefit in everyday life is usually assessed by retrospective questionnaires or ecological momentary assessments (EMA) comprising only subjective questions. However, questions in EMA about subjective speech intelligibility may be greatly influenced by the ability to lip read or to predict the spoken words from the context. Hence a measure for objective speech intelligibility in the typical environment of the hearing aid users would be useful.

Methods: To analyze the feasibility of an objective speech intelligibility test in real life, we performed an EMA study with 10 experienced hearing aid users (mean age 69.7 ± 11.1 years, 40.3 ± 21.5 dB PTA). Participants were provided with a smartphone and fitted with Signia 312Pure 7AX hearing aids using NAL-NL2, and closed coupling. After fine-tuning, a second program was configured with a 6 dB gain reduction from 0.5 to 4 kHz. The study period was 14 days plus four days of acclimatization. The hearing program was changed automatically each night by the app. Participants received notifications at six random times per day to fill out a questionnaire. Up to four additional daily notifications were issued in speech situations as classified by the hearing aids. Participants could initiate a questionnaire at any time.

The EMA questionnaire consisted of up to 22 questions targeting listening effort, current listening situation, and subjective speech understanding followed by a speech intelligibility test with 12 logatoms. At the beginning of the study participants adjusted the sound pressure level of the streamed logatoms to a comfortable volume. The logatoms are always in the order vowel-consonant-vowel and are in three different levels of difficulty with vowel “a” for level one, “e” for level two and “i” for level three. For each questionnaire four logatoms from each level were selected randomly from a total of 45 logatoms and streamed through the hearing aids. The speech intelligibility test could be skipped by giving a reason.

Results: A total of 1.131 questionnaires were collected. The speech intelligibility test had a median duration of 67.76 seconds (IQR 63.08–74.48) and was performed in 93.81% of the cases. While 37.49% of questionnaires were answered when participants were not actively listening to something, 25.38% were filled out during conversation and 25.02% while the radio or TV was playing.

Conclusion: This shows that a speech intelligibility test can be integrated in various situations in everyday life.