Evaluation of the mixing point in tinnitus sound therapy by a psychoacoustic matching protocol with a digital tinnitus evaluation system

Directive counseling and sound therapy have been reported to effectively alleviate tinnitus suffering. Without objective evaluation, researchers doubt the real effect of sound therapy. This study was designed to evaluate the frequency and intensity of the theoretical 'mixing point' (MP) in sound therapy and to investigate its relationship with the minimal masking level (MML) of tinnitus. The tinnitus tones of 133 patients were successfully matched in frequency (dominant in 4-10 kHz) and loudness (83.09 ± 12.04 dB) using a psychoacoustic matching protocol and a newly designed tinnitus evaluation system. The matching rate was 83%. The relationship between the MP and MML is described by a linear regression equation: MP = 0.90 x MML + 1.98 (r² = 0.82, p < 0.0001). The results of matching and correlation analysis confirmed the consistency of the MP in sound therapy. The psychoacoustic characteristics of tinnitus can be objectively evaluated with our matching protocol and evaluation system.