Remote Microphone Candidacy Study

2.0 Background / Literature Review / Rationale for the study:

Even when wearing well-fit hearing aids, many individuals with hearing loss continue to report difficulty communicating in background noise is one of the most common complaints of individuals with hearing loss. Directional microphones can improve speech perception in noise, but often fail to provide benefit in cases where the talker is distant from the listener, where there are multiple or moving noise sources, or in reverberation. Digital noise reduction may reduce listening effort and improve listening comfort, but has minimal effect on speech perception.

Placing the microphone in close proximity to the talker reduces the effective distance between speaker and listener, compensating for the effects of background noise and reverberation on the target signal. Use of a remote microphone can significantly improve signal-to-noise ratio (SNR), thereby improving speech perception in noise and at a distance. Recent studies demonstrated that remote-microphone devices that utilize adaptive digital technology (i.e, Roger) provide significantly more benefit for speech understanding in noise than non-adaptive remote microphones. Those advantages are likely related to the adaptive nature of the device, whereby the microphone gain varies according to the level of noise in the environment. In addition, interference is reduced via transmission of short digital bursts (160 μs) across a range of channels (2.4-2.4835 GHz). Further, the ability to utilize the hearing aids' onboard directional microphones in conjunction with a remote microphone gives listeners the benefits of remote microphone use without sacrificing nearfield intelligibility. The Roger system has also been shown to improve cell phone communication amongst cochlear implant patients.

Despite demonstrated advantages, use of remote microphone assistive devices among adults is low. In a recent study of listeners with severe hearing loss-a group which has substantial difficulty communicating in background noise, and is likely to receive significant benefits from remote-microphone devices-less than 10% reported use of a remote microphone. While cost may be a barrier for some users, even when such systems are available for free (as in the Veterans Administration), use is still low. One reason may be uncertainty among both providers and potential users as to expected benefit for a given listener. For example, Lewis et al. failed to demonstrate a clinically-significant benefit of remote microphone use using a work-life outcomes scale in a cohort of mostly nonworking (retired) participants. Wolfe et al. found significant improvements in objective speech recognition on average, but with a wide range of benefit (from 10% to 60% improvement across individual participants). That study also suggested that individual factors may affect remote microphone benefit, in that the magnitude of improved recognition was correlated with the ability to use spatial cues to improve recognition.

Research Locations:

All study tasks will take place in the Hearing Aid Lab and/or Northwestern's Center for Audiology, Speech, Language and Learning.

When testing in the Hearing Aid Lab, Frances Searle building room 1-451, we will either use the sound booth or lab space. All hearing related tasks take place in a sound booth which is a sound treated 8'x 8' room within the larger lab space. When taking histories or cognitive measures we will use the office space located within the lab or an additional nearby (i.e. same building) testing room. The additional test room is only used if participant confidentiality can be maintained (i.e. conversation is not audible to those outside the room). When using the Center for Audiology, Speech, Language and Learning all tasks will take place in a sound proof booth, in a clinical Hearing Aid fit room, or the virtual sound environment (ViSoR). ViSoR is a 16' by 14' by 9' space capable of simulating the acoustics and background noise properties of any environment by using an array of speakers.

Approach

The trial will use a within-subjects design consisting of baseline assessment (see assessments), hearing aid with Roger connect fitting, a four week trial period of use in the participant's everyday environment(s), and outcome measures.

Participants who qualify for a dome fitting will start their trial the same day as their baseline assessment. Participants who require a custom mold fitting will have earmold impressions taken at their baseline assessment and then be fit with the trial devices after the custom earmold has arrived back in the lab, usually about one week later. During an earmold impression the ear is visually inspected with an otoscope (magnifying scope with light). A cotton block and soft material are placed in the ear. The resulting impression created by the soft material is used to order an earmold for later testing. This is a standard clinical procedure.

A licensed clinical audiologist will perform the assessments, fitting and counseling of hearing aids and Roger system, and conduct the outcome measures. To ensure appropriate fit and use by the participants, there will be a follow-up one week after being fit with the devices. During this appointment participants will be evaluated and their hearing aid logging will be checked for compliance.

Hearing aid/Roger fitting: Trial hearing aids and clinically-appropriate earmolds or domes will be provided by Phonak at no charge to the participants for the duration of the trial. Those aids are expected to be drawn from Phonak's advanced technology level and to provide datalogging via 7 base programs. Aids will be set to NAL-NL2 targets using probe microphone measurements. Directional microphones will be enabled and verified via probe-microphone testing. Roger will be verified via probe-microphone testing, following clinical best practice. Appropriate hearing aid adjustments (as judged by the study audiologist) will be permitted to provide acceptable sound quality and loudness. Final REARs will be recorded. The study audiologist will instruct participants regarding hearing aid and Roger device use. PHAST-R and a Roger competency questionnaire (to be developed with input from Phonak) will be used to document understanding of device function at the fitting and one week follow-up appointments. Participants will then wear the hearing aids and use the Roger system for 1 month in their everyday listening environments. At the completion of the trial, participants will return to the lab for outcome assessments and to provide spontaneous feedback regarding their experiences. Hearing aids and remote microphone will be returned to the study site following completion of the trial.