Design and evaluation of back-end compressors for compressed content for cochlear implant users

Digital services allow users to access and consume media content such as movies and music at any time of the day using streaming technology over internet. Cochlear implant (CI) users are also among consumers of these digital services. One of the limitations of electric hearing with CIs is the narrow available electrical dynamic range (EDR). This work investigates the acoustic dynamic range (ADR) of streaming content and the necessity of designing a new back-end compressor for streaming and compressed content for CI users. Results from objective measures led to the design of three new back-end compressors; PC Streaming Voice Guard for high fidelity streaming scenarios, Tablet Streaming Voice Guard for streaming scenarios based on end user's limited sound reproduction system, and Music Streaming Voice Guard for music streaming. Results from perceptual evaluations in CI users showed a significant improvement in speech understanding for material with compressed ADR when using the new back-end compressors. Additionally, results gathered from the perception and appreciation questionnaires showed a significant improvement in the clarity of both the speaker's and the singing voice. Moreover, the overall enjoyment while using Tablet Streaming excerpts was significantly higher when using Tablet Streaming VG. Considering that Tablet Streaming VG provided significantly better or comparable results to the clinical compressor in all tested conditions, we recommend the use of this back-end compressor for streaming purposes and for content with a narrow ADR.