Verification Protocol for Signal Transparency Using the Cochlear Mini-Microphone 2+ and Digital Modulation Transmitter and Receiver with Cochlear Implants.

BACKGROUND: Guidelines established by the American Academy of Audiology (AAA) currently recommend behavioral testing when fitting frequency-modulated (FM) systems to individuals with cochlear implants (CIs). A protocol for completing electroacoustic measures on CI sound processors has not yet been established or validated when fitting either FM or digital-modulated (DM) systems, mini microphones, or mini microphones coupled to DM systems. In response, professionals have used or altered the AAA (2008) electroacoustic verification steps for fitting FM systems to hearing aids when fitting FM/DM systems, mini microphones, or mini microphones coupled to FM/DM systems to CI sound processors.

PURPOSE: The purpose of this research is to determine if the electroacoustic verification guidelines established by AAA (2008) for fitting FM systems to hearing aids are feasible and verifiable when fitting mini microphones and mini microphones coupled to DM systems to CI sound processors.

RESEARCH DESIGN: Electroacoustic measures were conducted on 51 Cochlear Nucleus 6/CP910 sound processors, one Cochlear Wireless Mini Microphone 2+ (MM2+), and one Phonak DM System (one Roger Inspiro transmitter and one Roger X receiver) using an adapted AAA (2008) protocol (Nair et al, 2017). Phonak's recommended default receiver gain setting was used with the Roger X receiver and adjusted if necessary to achieve transparency. Transparency refers to when the signal output of the device is the same when coupled and when not coupled to remote microphone technology.

STUDY SAMPLE: Electroacoustic measures were conducted on 51 Cochlear Nucleus 6/CP910 sound processors. In this study, the 51 Cochlear Nucleus 6/CP910 sound processors were either streaming to the Cochlear MM2+ or streaming to the MM2+ coupled to a Phonak DM system.

DATA COLLECTION AND ANALYSIS: In a clinical setting, using the AAA (2008) protocol for electroacoustic measurements when fitting FM systems to hearing aids, electroacoustic measurements using various equipment (MM2+ and Phonak DM system) were performed on 51 Cochlear Nucleus 6/CP910 sound processors using the Audioscan Verifit to determine transparency and verify DM advantage, comparing speech inputs (65 dB SPL) in an effort to achieve equal outputs. If transparency was not achieved when the CI sound processor was streaming to the MM2+ coupled to the Phonak DM system at the default receiver gain, adjustments were made to the Roger X receiver's gain. The integrity of the signal was monitored with the manufacturer's monitor earphones.

RESULTS: Using the AAA (2008) hearing aid protocol, when the Cochlear Nucleus 6/CP910 sound processor was streaming to the Cochlear MM2+, transparency was achieved for 50 of 51 CI sound processors. Again, using the AAA (2008) protocol when the Cochlear Nucleus 6/CP910 sound processor was streaming to the Cochlear MM2+ coupled to the Phonak DM system at Phonak's recommended default receiver gain, 28 sound processors achieved transparency. After the receiver gain was adjusted, the remaining 23 sound processors met transparency.

CONCLUSION: Electroacoustic measurements and transparency can be achieved for CI sound processors coupled to either a MM2+ only or to a MM2+ and a DM system by adapting the AAA (2008) guidelines.