[Introduction]  In the United States and Canada, about 2% of the population over the age of 45 and 8.5% over the age of 55 undergo hearing loss.  Thus, developing means to cure or assist hearing disabilities is important from medical and engineering standpoints.  In this study, a series of pilot studies were performed to visualize the sound with the purpose of (1) potentially developing a sound/music perceiving device and (2) discussing the sound conductance and human auditory system.

[Scientific motivation] Based on my experience of playing violin and taking videos, I noticed the strings of the violin show vibrating waves when captured by an old smartphone.  This experience of accidental discovery made me realize the meaning of sound being 'waves' and showed the potential usage of visualizing sound waves, and their conductance, for helping the people with hearing disabilities.

[Methods]  First, I captured a video image of the vibrating G string (thickest) with both iPhone 5 and 7 or digital camera, in all perpendicular angle directions, to test whether the replay of the captured video of the string shows the 'sound wave' formation.  Next, to test the sound conductance, the fume particle was observed under microscopy to monitor the particle vibration responding to the sound in the air.  Next, to visualize sound conductance at the air-to-liquid surface, particles of different sizes were observed in the water in response to the violin's sound. Finally, to understand hearing disabilities, I performed web search-based studies on human auditory systems and tried to interpret my data on the anatomical structure.

[Results] In the video visualization experiment, only when an old iPhone with a 'rolling-shutter' camera was used in the landscape orientation the 'sound wave' formation was captured on the video.  The vibration speed calculated from the captured wavelength was 159.4Hz (slightly offset from the actual 196Hz of the G string, explained below in the Discussions).  The microscopy experiment showed a striking particle motion of the air particle in response to a sound, but a significantly diminished response of water particles, suggesting the difficulty of sound conductance at the interface of air and water.

[Discussions] The fact that the sound and its conductance can be strikingly visualized showed a significant potential that the music or conversations, intangible to people with hearing disabilities, can be made tangible, helping them enjoy the music or conversations.  Even for the people with normal hearing abilities, the horizon of their perception can be significantly widened.  The fact that only the old iPhone, but not the new one, showed the 'sound wave' means that 'rolling shutter'-based image capturing is necessary.  The fact that there was an offset from the calculated vibration speed and the actual one of the G-string is likely because of the horizontal 'margins' of images not shown on the replayed images.  The difficulty of sound conductance at the air-to-water interface suggests the importance of several anatomical structures in the human auditory systems, including the tympanic membrane, ossicles (three small bones), cochlea, the cilial alignment of the inner/outer hair cells, tectorial membrane, etc.