remember this clip from a couple years back?

brainstorm! green needle! green needle! green needle! brainstorm! brain needle!

because these "words" are, in fact, not "words", but merely a low fidelity mishmash of frequencies emanating from a tiny speaker meant to represent "words", our ears cannot parse the sound and look for additional primes to interpret what we're actually hearing. and so when we think the voice is saying 'brainstorm', it becomes so, and when we think it's 'green needle', it also is thus.

same goes for this classic, commonly known as the mcgurk effect.

bah bah bah - vah vah vah - gah gah gah - dah dah dah

by replacing the video synced to the sound it completely changes how the sound is perceived. this change is real - nearly everybody will hear it the exact same way. what we see almost completely overrides what we know we are hearing. and then, just close your eyes, and instantly the sound is parsed correctly. our brains are hardwired to incorporate the additional information from our senses into our perceptions, and can't help but mislead us into hearing something not actually being said.

optical illusions trick our eyes with unnatural patterns, forced perspectives, etc. - tricking the ear is easier. in fact, it often tricks itself. your brain doesn't want to be overloaded by unnecessary audio information, and forces the ear to constantly readjust how it perceives the baseline of the sounds around you, expending less mental energy on the information it deems distracting or inessential. this is why it's helpful to switch monitors often while mixing - your ear adjusts to the frequency curve and response of one set of speakers, switch to another set to get a less biased listen; repeat as needed.

your brain also looks to help you understand the meaning of sounds when they are garbled or unclear, which helps explain the phenomenon of auditory pareidolia, i.e. hearing voices or words that aren't actually there. it's the audio equivalent of something humans have been doing for millennia - seeing faces in inanimate objects.

relatedly, there are tricks you can use in production and mixing that take advantage of the way the ear and brain work together. the idea isn't to fool the listener into hearing things that aren't there necessarily (though this can happen in certain cases, such as very lo-fi music), but rather to grab the attention of the listener by making their ears perk up or relax.

for example, let's say you have a very busy part of a song and you want one individual element to stick out, but simply making it louder doesn't sound right or work for whatever reason. what you can do is automate the part to be significantly louder for just the first second or so when it initially comes in, then turn it way down. this way, the ear grabs and tracks the frequency of the sound in the mix, even when it would have gotten lost and buried under other sounds without the cue.

another very simple tool is using one sound to mask issues with another one. this comes up all the time. i remember working on a song with an acoustic guitar part that had a little flub in the intro, and it was not possible to retrack or edit the part. i snuck a few high frequency atmospheric effects into the mix and immediately the flub was imperceptible to the ear - even if you knew it was there, your ear couldn't help perk up a little from the effect, and it was impossible to hear the error. similarly there was one song i worked on for a band where there was an odd timing issue during a transition and again, no edit was working - we mixed up a pad/string sound to grab + misdirect the ear during the section, the timing problem completely disappeared, and as a bonus we were left with a cool and unique part happening in the song for just a second, which is always a fun thing to do.

it's real important to understand how your ears can be tricked while mixing, and take steps to mitigate that. in the mixing process it can be super easy to overlook things - even big, glaringly obvious errors sometimes! - because we adjust to what we're hearing so quickly, and once our ears become accustomed to a sound profile it's easy to lose perspective on what frequencies should go where. this is why mix engineers utilize multiple sets of monitors, reference tracks, and even spectrum analyzers. sometimes these things are merely helpful; sometimes they're absolutely necessary. the good mix engineer knows when their ears are misleading them and finds ways and tools to continuously refresh their perspective.

there are other ways our brains and ears interact to odd effects (c.f. binaural audio, phantom rings, synthetic speech, etc.) - it's better to know something about what causes these phenomena rather than to be totally taken by surprise when encountering them. remember: thou art mortal. our senses exist to aid and protect us. they don't always give us a 100% accurate interpretation of the stimuli surrounding us.

but don't call it a deficiency or a shortcoming - it's how we work.

just some good things to know.

👻