Bibliography for the experiment design: 

Kim, H.W., Nam, H. and Kim, C.Y., 2018. [i] is lighter and more greenish than [o]: Intrinsic association between vowel sounds and colors. Multisensory Research, 31(5), pp.419-437. Available at: 10.1163/22134808-00002581 (Accessed: 14 Sep 2022)

Kwak, Y., Nam, H. and Kim, C.Y., Crossmodal correspondence between haptic shape and sound.Journal of Vision 2018;18(10):97. doi: https://doi.org/10.1167/18.10.97. (Accessed: 16 Sep 2022)

Ward, J., Huckstep, B. and Tsakanikos, E., 2006. Sound-colour synaesthesia: To what extent does it use cross-modal mechanisms common to us all?. Cortex, 42(2), pp.264-280. Available at: https://doi.org/10.1016/S0010-9452(08)70352-6 (Accessed : 04 April 2021)

Wrembel, M., 2007, August. Still sounds like a rainbow-a proposal for a coloured vowel chart. In Proceedings of the Phonetics Teaching and Learning Conference PTLC2007 (pp. 1-4). London, UK: University College London. Available at: https://www.phon.ucl.ac.uk/ptlc/proceedings/ptlcpaper_14e.pdf (Accessed 04 May 2022)

Ramachandran, V.S. and Hubbard, E.M., 2001. Synaesthesia--a window into perception, thought and language. Journal of consciousness studies, 8(12), pp.3-34. Available at: http://cbc.ucsd.edu/pdf/Synaesth_JCS.pdf  (Accessed : 04 Sep 2021)