Unpleasantness of Amplified Environmental Sound Used in Tinnitus Sound Therapy: A Preliminary Study of Clinical Assessment

Abstract

Objectives: In this study, our aim was to use environmental sounds amplified in the frequency region corresponding to the tinnitus frequency of individual patients and apply them as sound therapy in tinnitus retraining therapy (TRT). In this pilot study, we 1) investigated the unpleasantness of processed environmental sounds using the amplification, attenuation, and removal in different frequency regions; 2) compared the unpleasantness of processed sounds for older and younger groups of participants; and 3) determined the amplification level appropriate for a clinical test.

Materials and methods: We processed the sound of a river with three types of modification (amplified, attenuated, and notched) at a one-octave width of seven central frequencies, in the range 250-8000 Hz. Amplified and attenuated sounds were processed with five positive gains (+6, +12, +15.6, +18, and +20 dB) and two negative gains (-6 and -12 dB). Twenty-three older participants and 23 younger participants rated the unpleasantness of sounds using a visual analog scale.

Results: We found that, in the older group, there was no difference in unpleasantness among the three modifications. Older participants rated the level of unpleasantness as lower than younger participants for processed sounds in the high-frequency region. There were no marked differences among the amplification levels in the group of older participants.

Conclusion: Based on the results, we decided that our clinical study would target older patients who had a tinnitus frequency over 4000 Hz and would compare the effect of an amplified sound with a 20 dB gain at the frequency corresponding to individual tinnitus with notched sound.

Figure 1. a, b

Long-term average spectrum of sound stimuli. (a) Processed sounds with amplification. Solid line: original (unprocessed sound). Dotted line: amplified with 6 dB at 2000 Hz. Dashed line: amplified with 20 dB at 2000 Hz. (b) Processed sound with the attenuation and notched sound. Dashed line: attenuated with 6 dB. Dotted line: attenuated with 12 dB at 2000 Hz. Solid line: removed at 2000 Hz.

Figure 2

Experimental procedure, showing the section for changing the sound volume and the experimental evaluation.

Figure 3

Mean unpleasantness values at each central frequency for the original sound and for the processed sound with each of the three processing methods. Error bars indicate the standard error.

Figure 4

Mean unpleasantness values of each processing condition for older and younger age groups. Error bars indicate the standard error.

Figure 5

Mean unpleasantness values of each frequency condition for older and younger groups, as well as the auditory threshold of each frequency obtained from 11 participants of the older and younger age groups. Error bars indicate the standard error.

Figure 6

Mean unpleasantness values of each amplification level. Error bars indicate the standard error.