Over the past three terms, I've become aware of a strange connection between sounds and visual images in my mind. When lying in bed and trying to fall asleep, with my eyes closed and thoughts mostly empty, I frequently experience visual patterns in response to loud or sudden noises. The first time it happened, my roommate's Macintosh computer emitted an unexpected and loud 'bonk' noise as an alert. Simultaneously, a diagonally oriented field of wavy white and black lines flashed before my eyes. The intensity of the pattern varied smoothly from black to white, so no clear delineations were perceivable. I estimate that there were about twenty to thirty of these lines visible, to give some representation of their density.
The perception lay somewhere between reality and imagination; not a concrete object in the world, but also not a "minds eye" sort of projection. It's analogous to the experience of seeing whorls and cascades of shadowy color when you press on your eyeballs for a few minutes, except it occurred suddenly, and faded as quickly as the sound. It also feels like there's an extra component to the experience, as well: it's not just a field of lines, but a visual feeling of orientation. That bit is much harder to describe or even verify, but it does seem present.
At first I thought I was hallucinating, or deceiving myself. Yet the experience surprised me time and time again, and has been consistent: it's happened twice this week. Door slamming, alert sounds, even ceramic mugs being set down on a wooden desk: all have associated unique visual patterns. The intensity, orientation, density, and waviness of the lines seems correlated with the character of the sound: the mug, for example, evoked a short-lived, vertical, dense, and straight field of lines. Sometimes I see cross-hatching, or a simple uniform flash. I plan to record these experiences from now on, and will try to characterize the relationship in more detail.
I wonder if this happens to anyone else.
June 1st 2007: Andy Howe confirms that he also has noticed cross-hatch patterns with loud noises before sleep.
Hello! Your description of hypnagogic synaesthesia came up when I googled for the phrase, while wondering if anyone else had the same thing. Your experience sounds exactly the same as mine - right down to the diagonal lines! I often find that they’re a bit zigzaggy, and they sort of wax and wane with the amplitude of the sound.
I googled the same thing, ended up here. Although in my case there have always been a bright white flashing light that lasts for the fraction of a second that the sudden noise does. Right after that my heart starts beating faster for a few seconds, I guess it’s normal given the unexpected nature of a loud noise that engages our adrenaline levels in case of any imminent danger…