Notched Noise Therapy for Suppression of Tinnitus

Tinnitus is the most prevalent service-connected disability for Veterans. Many Veterans are offered sound-based (acoustic) therapy for tinnitus that is intended to alter the tinnitus perception and/or reactions to tinnitus in a clinically beneficial way. Various methods of acoustic therapy are in use and companies are promoting different products. It remains unknown; however, how certain acoustic parameters may be more effective than others. Recent research has shown the benefit of one such acoustic therapy, Notched Noise Therapy, that presents wideband sound with the tinnitus frequency region notched out, theorized to distribute lateral inhibition into the notched frequency region to suppress neural activity believed to cause the tinnitus percept. Previous studies have typically involved brief daily exposures, which are not as likely to remodel neural processes underlying tinnitus as is continuous "immersion" in background sound, which is adopted here. The proposed study will conduct a randomized controlled trial to evaluate the efficacy of notched noise therapy (NNT). The long-term goal of the research program is to develop an accessible, evidence-based treatment that reduces tinnitus loudness and to be able to assess that treatment through a validated method of behavioral and physiological clinical tools. The overall objective for this CDA-2 research plan, which is the next step toward attainment of the investigators' long-term goal, is to systematically evaluate the utility of functional, psychoacoustic, and electrophysiologic measures to reveal the overall whole-health impact in Veterans with chronic tinnitus. The trial will enroll 108 participants, who will be randomized to one of three acoustic therapy methods: amplification + notched noise, amplification + noise without notch, and amplification-only. The three groups will be asked to wear ear-level devices (combination instruments that provide both amplification and 1-10 kHz shapeable noise) as much as possible during waking hours. All participants will undergo acoustic therapy for 8 weeks and will complete outcome measures (i.e., Tinnitus Functional Index, Psychoacoustic loudness and pitch matches, AEP, and EEG measures) at baseline and at 4 and 8 weeks. They will repeat outcome assessment at 12 weeks to evaluate for maintenance of any effects while not receiving acoustic therapy for 4 weeks. (Participants requiring hearing aids for hearing loss will continue to use their aids during the 4-week no-treatment period). The investigators hypothesize that NNT suppresses tinnitus perception by distributing lateral inhibition into the notched frequency region and will therefore, reduce the perception of tinnitus loudness. At the completion of this CDA-2 program, the expected outcomes include a NNT as a therapy for tinnitus and the contributions that it may have on tinnitus perception as well as a solid training foundation for a successful VA research career. These results are expected to have an important positive impact because they will not only provide insight into the true reactionary and perceptual benefit of an intervention, but a treatment evaluation protocol will be determined, ultimately providing a foundation for the development of evidence-based acoustic therapies to treat tinnitus, a critical component and goal of Veteran tinnitus care.

Inclusion criteria

Candidates must meet the following inclusion criteria to qualify:

• Veteran
• no active middle-ear disease
• at least one air conduction hearing threshold of 40 dB HL or worse in each ear between .25-8 kHz as measured at the first study visit
• unilateral or bilateral constant tinnitus
• index score on the Tinnitus Functional Index (TFI) of at least 25 (out of a maximum score of 100)
• a score of 24 or higher on the Mini Mental State Exam (MMSE)
• a tinnitus pitch match between 2-10 kHz (and achieve desired level of precision as described below in 3.3 Study Procedures, Tinnitus Psychoacoustic Assessment)
• demonstrates understanding of the requirements of the study
• motivated and capable of participating (including ability to communicate in English)

Exclusion criteria

The following exclusion criteria will be used:

• two or more hearing thresholds exceeding 70 dB HL
• significant conductive hearing loss-defined as an air-bone gap of 15 dB at more than two frequencies in one ear, or an air-bone gap greater than 15 dB at any one frequency
• suspicion of secondary (somatic) tinnitus, Meniere's disease, or tinnitus potentially related to temporo-mandibular disorder or whiplash (any of which can be ruled out with an examination by an appropriate physician)
• any mental, emotional, or health conditions that would preclude full study participation