Voice Telephony for Individuals with Hearing Loss: The Effects of Audio Bandwidth, Bit Rate and Packet Loss

This paper describes three studies conducted with a total of 114 individuals with hearing loss and 12 hearing controls, with the goal of investigating the impact of audio quality parameters on the accessibility of voice telecommunications. Three categories of parameters are covered: ( 1) narrowband (NB) versus wideband (WB) audio; (2) encoding audio at varying bit rates, ranging from typical rates used in today's telecom networks to the highest quality supported by these audio codecs; and (3) absence of packet loss to worst-case packet loss in VoIP telephony. With WB audio, individuals with hearing loss exhibit better speech recognition, expend less perceived mental effort, and rate speech quality higher than with NB audio. Bit rate affects speech recognition for NB audio, and speech quality ratings for both NB and WB audio. Packet loss affects all of speech recognition, mental effort, and speech quality ratings. WB versus NB audio also affects hearing individuals, especially under packet loss.