Objective: To test, whether modern Internet telephony with a broadband transmission (0.1-8 kHz) of speech improves speech perception in comparison to conventional telephony (0.3-3.5 kHz) in hearing-impaired and normal-hearing adults.
Study design: Experimental clinical study.
Setting: Audiologic laboratory in a tertiary referral center in Bern, Switzerland.
Patients: Twenty-one adult hearing-impaired patients consisting of 11 users of cochlear implants and 10 users of hearing aids were selected from the institution's database based on pure tone audiograms, speech perception scores, and device settings. Ten normal-hearing adults served as controls.
Intervention: Superiority trial of speech perception assessed with Internet versus conventional telephone quality and noninferiority trial of Internet telephone versus frequency restricted, uncompressed audio CD quality. A modern broadband codec was chosen to simulate Internet telephone quality, and ideal network conditions without packet loss were assumed.
Main outcome measures: Speech perception scores of a monosyllabic word test in quiet and a sentence test in background noise assessed in different audio qualities.
Results: : Test scores were, on average, 15% (4-33) higher in the monosyllabic word and 25% (8-51) higher in the sentence test using Internet versus conventional telephone quality across all subject groups. Speech perception was not significantly different when Internet telephone quality was compared with high-cut CD quality.
Conclusion: Internet telephony offers significantly improved speech perception to hearing-impaired and normal-hearing adults under ideal laboratory conditions through doubling the frequency range and through conserving audio quality during digital sound processing.