How Brain Waves Surf Sound Waves to Process Speech(nautil.us)
nautil.us
How Brain Waves Surf Sound Waves to Process Speech
http://nautil.us/blog/how-brain-waves-surf-sound-waves-to-process-speech
10 comments
I'm baffled by the video of a sound that can be heard as either "green needle" or "brainstorm," depending on which word one imagines while listening to it. They don't even have the same number of syllables. I'd like to know what's going on in the brain to create this auditory illusion. https://www.youtube.com/watch?v=5pRY3wlKwm8
First I heard brainstorm, then green needle and then brain needle, ha ha! Yeah that was weird!
Found a related video that talks a bit about this sort of thing: https://www.youtube.com/watch?v=yDiXQl7grPQ
Also related is this one that I remember seeing on HN or Reddit a while back: https://soundcloud.com/whyy-the-pulse/an-audio-illusion. There is an article about that one as well at https://gizmodo.com/this-audio-illusion-will-make-you-never-... but I never bothered to read the article because I think the audio recording is sufficiently interesting in its own right.
Found a related video that talks a bit about this sort of thing: https://www.youtube.com/watch?v=yDiXQl7grPQ
Also related is this one that I remember seeing on HN or Reddit a while back: https://soundcloud.com/whyy-the-pulse/an-audio-illusion. There is an article about that one as well at https://gizmodo.com/this-audio-illusion-will-make-you-never-... but I never bothered to read the article because I think the audio recording is sufficiently interesting in its own right.
I tried to skipping immediately to the sound (0:02) that said the words and found that I couldn't hear "brainstorm" no matter how hard I tried, it seems like the whole noise needs to be heard to effectively reset and let the user hear the other word.
I wonder if the results would be different if the study subjects were people who often listen to podcasts or audiobooks in faster speed settings.
That's an interesting hypothesis. I listen to audiobooks at 2 or 3 times speed, depending on the clarity of the readers voice. When I first heard the "green needle" vs. "brainstorm" audio, I heard "brainstorm" once but then the pitch of the audio seem to shift up and I could only hear "green needle" after that. The change in audio quality was similar to what I've experienced when listening to a book at 1X speed and then shifting it up to 2X or 3X. I haven't been able to reproduce this though. Now the recording always sounds like "green needle" to me.
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Interesting. I'd like to hear more about this "entrainment" concept mentioned. How does the brain know what the "envelope" is? Sounds like magic.
It's the peaks in the spectral domain. The cochlea is lined with little hairs that are tuned to different frequency bands. When they're stimulated by sound waves, the nerves they're attached to create tiny electrical impulses which propagate into the larger networks of neurons that make up the auditory cortex.
When a neurophysiologist uses the term "entrainment" it usually means that they either observe neuronal firing rates or spectral content of energy over populations that is somehow directly influenced by properties of the auditory or visual stimulus. In cases like this, it's like "we played an x hertz tone and shortly after stimulus onset we saw energy at x hz appear in a population of neurons"
When a neurophysiologist uses the term "entrainment" it usually means that they either observe neuronal firing rates or spectral content of energy over populations that is somehow directly influenced by properties of the auditory or visual stimulus. In cases like this, it's like "we played an x hertz tone and shortly after stimulus onset we saw energy at x hz appear in a population of neurons"
Perfect explanation, thank you.
Interesting enough :P