Edit: It has come to my attention that "Critical Flicker Frequency" only applies to vision, but the perception of time of animals is measured by this method and i didn't know how to phrase this otherwise, though it's obvious that different species experience the flow of time differently, including some that can tweak it's own according to it's metabolism, and this is what i'm trying to address, i'm sorry if i wrote a confusing question.

In the world i'm developing, other than the genetically modified protagonist that has superhuman control over her own body, this "bullet-time" could also be achieved through by the use of a specific drug, somewhat like Fallout's "Turbo", though i'm not interested in specifying it's composition but rather describe it's effects.

Would accelerating/deccelerating our perception of time dislocate the ear's range of audible frequencies enabling us to hear frequencies under/above the human hearing range?

Or would we hear the same sounds but accelerated/deccelerated, and thus, higher/lower pitched?

  • 3
    $\begingroup$ Please mind which tag you pick. This is not a reality check question. That said, Critical Flicker Frequency is a concept in the psychophysics of vision. What has to do with hearing? $\endgroup$
    – L.Dutch
    Jun 30, 2022 at 17:14
  • $\begingroup$ Then what is the equivalent ""frame rate"" measurement for the other senses? $\endgroup$ Jun 30, 2022 at 17:41
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    $\begingroup$ it's your question, you have to tell us. $\endgroup$
    – L.Dutch
    Jun 30, 2022 at 17:45
  • $\begingroup$ This is not how hearing works, like, at all. (And even for vision, the flicker fusion threshold is not comparable to a frame rate; in particular, it is significantly higher than the image fusion threshold. For example, standard cinema rate of 24 images per second is perfectly good enough to fuse the images into the illusion of smooth motion; but in order to eliminate the perception of flicker, cinematographic projectors are made to show each image twice.) $\endgroup$
    – AlexP
    Jun 30, 2022 at 17:56
  • $\begingroup$ Think what a "perception rate" for hearing would imply. It cannot be between about 16 and about 16,000 hertz -- because that would be audible as a tone, and we know that there are no gaps where it could hide. It is very obviously not below 16 Hz -- we can clearly sounds of shorter duration than that. $\endgroup$
    – AlexP
    Jun 30, 2022 at 19:01

3 Answers 3


Case #1: Our subject is experiencing time faster

The drug speeds up not just the subject's metabolism, but actually speeds up the experience of time for the subject. Having taken the drug at age 20, the next 80 years of the subject's life are lived in the next 80 hours. How would this affect their perception of sound?

They wouldn't hear anything. From the subject's point of view, everyone and everything just stopped moving. Sound would be shifted to frequencies so low that the subject couldn't hear them. They might feel the sound (in the same way we can "feel" the sound from a sub-woofer), but the subject wouldn't hear anything. It would all be outside his/her range of hearing.

Example from existing SciFi: Star Trek TOS: Wink of an Eye

Case #2: Our subject is experiencing normal time, but is capable of perceiving greater detail

The drug doesn't change how the subject experiences time. Our 20-year-old subject will live the next 80 years in the expected 80 years. But our subject is capable of perceiving life around them in much greater detail. The processing power of the brain is increased such that the subject can comprehend the passing of a bullet and describe its passing with the same detail that the undrugged might a passing car or a dog that ran past us.

Ignoring the possibility that the subject's brain might explode... or melt and run out his/her ears... the most likely side-effect of this drug is that they'd become intensely forgetful! So much information would be fed into the subject's head that his/her ability to store the details of living life would be compromised in the same way that most of the details that we experience in an average day are forgotten by the next morning. The subject might have trouble remembering their own name after a couple of hours because it wouldn't be just the bullet they're noticing in hyper-detail, but the rest of life around them.

But how would this affect their perception of sound? I believe in this case they would hear sound in the normal range of frequencies — but they'd notice every little detail: all the background noise, every variation from expected norm (such as every not-quite-right-note sung by a singer), every whir of a fan underneath whatever it is you're trying to listen to. It would be maddening.

Example from existing SciFi: Star Trek: Insurrection (attribute of the Ba'Ku))

NOTE: Hearing doesn't have a "flicker rate" or anything like it

Have you ever watched an old 16mm movie? When you watch the film pass in front of the light, you'll notice that the film actually stops for a moment. What you're seeing on the screen isn't motion, but the illusion of motion by passing a series of still pictures in front of your eyes fast enough that your brain interprets it as motion.

Modern computer-generated imagery is no different. It's quality is higher, but you're still seeing a series of still images generated so quickly that your eye thinks its seeing motion.

What's funny is that we don't really know how the brain stores visual imagery. This is important! Because we're using video as an example of what might be done with audio — except that we don't know what the brain is really doing, we just now how to fool it into thinking it's seeing motion.

We don't have that problem with audio.

We can't create continuously-moving video that's separate from the refresh rate of a monitor (or film...). But we can create continuously-varying audio. That's why other users have commented that hearing doesn't work that way. Actually, our brain probably stores audio and video in the very same way — but because we can create continuously-varying audio, we don't have to "slice" the audio up into chunks to fool the brain.1

So, no, there's no equivalent of a "flicker frequency" or "frame rate" or any other such thing when it comes to the perception of audio by the brain. But, to be fair, there's no such thing (insofar as I know) for video, either! The problem isn't how the brain perceives video. The problem is that we don't know how to create continuous-motion imagery.

1When we digitize music, we slice it up and then do some funky stuff with electronics to recreate the continuously-variable music. This isn't the same thing as the series of still images on a video screen. The human ear isn't hearing the "digital slices" of audio. It's hearing the recombined data. Just wanted to avoid a question. Thanks for tuning in!

  • $\begingroup$ Yes, that's why i thought that the frequencies you hear might be distorted, like every wave of the frequency counts as a frame, do you get what i mean? $\endgroup$ Jul 1, 2022 at 16:38
  • $\begingroup$ @PauloRaposo Yes, I figured from your comments that you thought it might be that way. $\endgroup$
    – JBH
    Jul 2, 2022 at 2:44

Would accelerating a person's perception of time dislocate the range of audible frequencies or make what they hear sound deccelerated, and thus, lower pitched?

As it often happens... it depends.

If you had the whole organism living in "accelerated time" (e.g. as in Wells' The New Accelerator, or Charles Sheffield's Proteus series, or Between the Strokes of Night), you'd hear lower-pitched sounds and even see red-shifted light.

But that's not exactly how accelerated perception works. Normally, the whole I/O depends on electrochemical phenomenons which you simply cannot "accelerate", or the likely end result is one dead organism. The same secondary effects observed by Wells would apply, in spades, to the whole organism.

What usually happens is that the organism already has a "faster" perception mode available, which it uses at the lowest setting to save energy. A lot of information gets selected, discarded and distilled at each stage, allowing the next ones to perform more efficiently; perhaps the greatest bottleneck is in the brain, which is massively parallelized.

So your "accelerated" perception would be in all likelihood caused by an increased dedicated computational capacity (possibly at the expense of other brain sections). The signals would arrive at the usual speed and with their usual features, but they would be perceived much faster, and their meaning would be immediately available.

So you would both hear the correct sounds - no shift in pitch - and have the sensation of the world having slowed down. Also, your body would feel awkward and bogged in molasses. Your movements would become jerky, because you don't compensate very well (this might improve with practice, though).


Quite simply, all frequencies would become lower by the ratio of the speed-up. Good human hearing (for the young) is about 20-20,000Hz (cycles per second). If your subjective time experience doubles, that range would shift to 40-40,000Hz. You'd hear a lot of strange things on the high end, but wouldn't miss much on the low end. Make it 50X, though, and your range goes to 1,000-1,000,000Hz. It would be hard to understand human speech (even if you had the patience), but you'd be able to hear some AM radio stations directly in the presence of metal.


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