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. 2021 Feb 1:12:626762.
doi: 10.3389/fpsyg.2021.626762. eCollection 2021.

Low-Intensity Steady Background Noise Enhances Pitch Fusion Across the Ears in Normal-Hearing Listeners

Yonghee Oh  1 , Sabrina N Lee  1
Affiliations

Low-Intensity Steady Background Noise Enhances Pitch Fusion Across the Ears in Normal-Hearing Listeners

Yonghee Oh et al. Front Psychol. .

Abstract

Binaural pitch fusion is the perceptual integration of stimuli that evoke different pitches between the ears into a single auditory image. This study was designed to investigate how steady background noise can influence binaural pitch fusion. The binaural fusion ranges, the frequency ranges over which binaural pitch fusion occurred, were measured with three signal-to-noise ratios (+15, +5, and -5dB SNR) of the pink noise and compared with those measured in quiet. The preliminary results show that addition of an appropriate amount of noise can reduce binaural fusion ranges, an effect called stochastic resonance. This finding increases the understanding of how specific noise levels can sharpen binaural pitch fusion in normal hearing individuals. Furthermore, it elicits more pathways for research to explore how this benefit can practically be used to help improve binaural auditory perception.

Keywords: binaural auditory processing; binaural fusion; pitch; steady pink noise; stochastic resonance.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Example adaptive tracking results for one representative subject in the quiet condition. Left panels show two separate interleaved tracks in one testing block. Upper panel and lower panel show the adaptive tracking results when the comparison tone frequencies were presented above and below than the 2-kHz reference, respectively. Circle and cross symbols indicate different (not fused) and same (fused) responses, respectively. Right panel shows an estimated fusion function (thick solid line) and a fusion range (line with double arrows) calculated as the frequency offset between the two thresholds with 70.7% confident.
Figure 2
Figure 2
Fusion range results in the quiet [∞ dB signal-to-noise ratio (SNR)] condition. (A,C) Example two-dimensional representations of fusion range results for one representative subject (N2) at the reference frequency of 2kHz (A) and 3kHz (C). The diagonal dashed line indicates the same frequency between two ears. (B,D) Individual fusion range results at the reference frequency of 2kHz (B) and 3kHz (D) indicated by horizontal dotted lines. The red lines/bars show fusion ranges in the right ear when the left ear is presented as the reference ear. The blue lines/bars show fusion ranges in the left ear when the right ear is presented as the reference ear. Error bars of endpoints represent across-trial SDs. The horizontal solid lines inside the boxes show the fusion centers.
Figure 3
Figure 3
Averaged fusion range and fusion center results at the reference frequency of 2kHz (A) and 3kHz (B) as a function of SNR (∞, +15, +5, and −5dB SNR). ∞ indicates no background noise condition. Filled symbols and open symbols indicate fusion ranges in the left y-axis labels and fusion centers in the right y-axis labels, respectively. Red and blue colors represent fusion ranges in right and left ears, respectively. Error bars represent standard deviations of the mean. Asterisk symbols at the top indicate significant differences in fusion ranges (***p < 0.001).
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