(PP306) Electroacoustic Verification of the Easy Gain Settings in the Remote Microphone System

    Remote microphone systems are designed to facilitate communication by increasing the signal-to-noise ratio through a transmitter and a receiver. Adjusting Easy Gain (EG) settings on the digital-modulated (DM) receiver may be necessary to improve the audibility of the signal from the transmitter. Effects of EG settings were evaluated with electroacoustic verification in a Roger DM system as a function of the degree of hearing loss and receiver types. The preliminary study showed an interaction between the EG adjustments and the degree of hearing loss.

Summary: 

Objective

The purpose of this study was to evaluate the electroacoustic output through a digital-modulated (DM) system including the Roger receiver, hearing aid (HA), and transmitter based on different Easy Gain (EG) settings, varying levels of hearing loss (HL), and multiple receiver types.

Rationale

Rapid advances in assistive listening devices are occurring in the signal processing of remote microphone systems from frequency-modulated (FM) to DM systems. In the FM system, a technology named “FM Advantage” (FMA) can provide an extra benefit in the signal-to-noise ratio for both cochlear implant (CI) and hearing aid (HA) listeners. In the DM system, a similar technology named “Easy Gain” can also adjust the output (+8 to -8 dB), which might provide an equal benefit to FMA.

Design

The primary equipment contained two HAs (a Phonak Naida V90 SP and a Naida V90 UP), three types of DM receivers (two Roger X(02), two Roger 18, and two Roger 19), and a transmitter (Roger Touchscreen). All tests were completed in a Fonix 8000 Hearing Aid Test System. There were five listening conditions from a flat 40 to 80 dB HL, 10 dB steps, and nine EG settings from +8 to -8 dB, 2 dB steps. For each listening condition, HA verification was performed based on ANSI S3.22 (2003); each root-mean-square (RMS) output of the six receivers was tested with the nine EG settings.

Results

As EG changed by 2 dB, the output changed 2 dB (±.5 dB) only for the 40 dB HL condition. As HL increased, the change in output was typically less than 2 dB for EG settings > 0 dB. With a greater degree of HL, HA compression would have greater effects on the output for EG settings > 0 dB. The mean output of integrated receivers (both Roger 18 and Roger 19) was generally greater than that of Roger X (02) receiver, with mean = 2.03 dB and 3.14 dB, respectively.

Conclusion

The three factors, including EG settings, degree of HL, and DM receiver-type, interact with each other such that electroacoustic verification is necessary to determine appropriate settings.