J Audiol Otol.  2020 Oct;24(4):174-179. 10.7874/jao.2019.00507.

Investigating the Effects of Hearing Loss and Hearing Aid Digital Delay on Sound-Induced Flash Illusion

  • 1Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran
  • 2Department of Biomedical Engineering, School of Electrical and Computer, Islamic Azad University, Tehran, Iran
  • 3Department of Telecommunication, School of Engineering Boushehr Branch, Islamic Azad University, Boushehr, Iran


Background and Objectives
The integration of auditory-visual speech information improves speech perception; however, if the auditory system input is disrupted due to hearing loss, auditory and visual inputs cannot be fully integrated. Additionally, temporal coincidence of auditory and visual input is a significantly important factor in integrating the input of these two senses. Time delayed acoustic pathway caused by the signal passing through digital signal processing. Therefore, this study aimed to investigate the effects of hearing loss and hearing aid digital delay circuit on sound-induced flash illusion.
Subjects and Methods
A total of 13 adults with normal hearing, 13 with mild to moderate hearing loss, and 13 with moderate to severe hearing loss were enrolled in this study. Subsequently, the sound-induced flash illusion test was conducted, and the results were analyzed.
The results showed that hearing aid digital delay and hearing loss had no detrimental effect on sound-induced flash illusion.
Transmission velocity and neural transduction rate of the auditory inputs decreased in patients with hearing loss. Hence, the integrating auditory and visual sensory cannot be combined completely. Although the transmission rate of the auditory sense input was approximately normal when the hearing aid was prescribed. Thus, it can be concluded that the processing delay in the hearing aid circuit is insufficient to disrupt the integration of auditory and visual information.


Hearing loss; Auditory-visual integration; Sound-induced flash illusion; Hearing aid; Temporal coincidence
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