When we strain to hear, what is strained?
December 17, 2019 8:41 PM   Subscribe

When you thought you heard a faint noise, and you strain to hear it again, are you straining some physical part of your ear, or are you straining your brain to filter the noise and pick out that sound from the background?

(This question has been brought to you by: Cannabis.)
posted by Pastor of Muppets to Science & Nature (14 answers total) 10 users marked this as a favorite
 
I think you are focusing more intently on the noise and filtering out other sounds (straining your brain).
posted by any portmanteau in a storm at 8:46 PM on December 17, 2019 [4 favorites]


Strain, as in "force yourself to make a great effort". Not strain, as in "Purple Kush".
posted by theory at 8:51 PM on December 17, 2019 [4 favorites]


Do you ever have the sensation of your inner ear flexing? I suspect it’s both your brain and you ears!
posted by amanda at 8:54 PM on December 17, 2019 [1 favorite]


I do feel like something is flexing but I don't know if it's my inner ear, my ...skin? as my brain ramps up, or like a muscle that would have twisted a proto-simian ancestor's ear like a cat's.

Oh and no, I know what "strain" means, and not like kush ;)
posted by Pastor of Muppets at 8:59 PM on December 17, 2019


I'd be interested to hear from someone who knows ear stuff well whether there's any specific mechanism analogous in some way to squinting one's eyes (which does meaningfully sharpen focus a bit by reducing incoming peripheral light rays).

But there's also a lot of other little subtle things you might do while straining to hear: change/loosen the set of your jaw, still your body, turn one ear or the other toward the perceived sound, calm your breathing, etc. And focusing your attention as a sheer mental exercise, yeah. All of which feels like a reasonable argument toward a more figurative interpretation of "strain" as a kind of effort of willfulness rather than of muscle.

More generally, a figurative interpretation of "straining to hear" makes sense, even if there is some mechanism of ear canal muscle contraction or whatever at play, if that mechanism isn't commonly known and understood; language by default tends to serve common understanding, and a common shared figurative understanding usually means the meaning in practice is figurative whatever etymological roots or technical/jargon correlations might exist.
posted by cortex at 9:44 PM on December 17, 2019 [6 favorites]


I know that for me a large part of straining to hear is slowing or shutting down other body functions (e.g. breathing) to stop the extra noise.
posted by Tell Me No Lies at 10:36 PM on December 17, 2019 [2 favorites]


This is a great question. And as is often the case with these things, the answer is in most cases probably a little bit of both.

Processing sound within the brain is actually an extremely complex topic, with important details still an active area of research. But there absolutely are significant effects of "top-down control" over low-level auditory processing that can help you detect faint sounds from a noisy background. An often-cited example is the "cocktail party effect," where you can carry on a conversation with someone while other people are speaking in the background and not really hear anything from the background noise, until someone in the background says your name. Voluntary attention is another example, and this can feel effortful in the same way that any focused attention does. Why exactly focused attention feels effortful is still something of an open question, but may have something to do with the energy demands of an active brain.

But in addition to this sort of "mental strain," there are also active mechanisms that can change the acoustic properties of the inner ear to "tune" it for sound detection. Many of these function to filter out noises you generate yourself, which otherwise would be overwhelmingly load compared to the sounds you're trying to hear. The tensor tympani muscle, for example, acts to dampen the eardrum while you chew, reducing the volume much like placing your hand on a drum head dampens it. But your question is about straining to increase your sensitivity to certain sounds. And here too there are mechanisms for tuning the sensitivity of the inner ear, by altering the electromechanical properties of the hair cells in the cochlea. This is pretty complex and not my area of expertise at all, but there's a full-text review paper from a few years ago describing what was then the state of knowledge on the subject. But basically, your ear can become more or less sensitive to specific frequencies of sound using this mechanism, providing an active and dynamic acoustic filter.
posted by biogeo at 11:17 PM on December 17, 2019 [24 favorites]


What an interesting question!

I am convinced after trying it out for a while, that when I strain to hear, the muscles in my ear are doing something out of the ordinary — the sensation has a family resemblance to the feelings I get when I rumble my ears as I yawn or am getting ready to sleep.

The smallest skeletal (aka 'voluntary') muscle in the body, the stapedius muscle, diminishes the loudness of sound by pulling the smallest bone in the body out of the chain of sound transmission in the ear; Bell's palsy can paralyze this muscle by blocking nerve impulses to it, and people with Bell's often report that ordinary sound is painfully loud on the affected side, so perhaps it's not too much to guess that the stapedius is usually under some tension, and that when you want to hear as well as possible, you relax the stapedius muscle as thoroughly as possible — as well as maybe doing something with the tensor tympani muscle, but I don't know what action would render hearing most acute there.
posted by jamjam at 11:22 PM on December 17, 2019 [2 favorites]


Folklore has it that people unconsciously or consciously open their mouths slightly, swallow, or yawn to attend better to sound. This would equalize pressure inside and outside the ear via the Eustachian tube. Sci Am article.
posted by gregoreo at 12:35 AM on December 18, 2019


Great question! I sing in a choir, and I've noticed there's a specific thing I do when I'm straining to hear either a note from the piano or my own voice among the others. I look up and to the side, and tilt my head, jutting my chin forward. It helps! Just an anecdote, and would love to hear an explanation!
posted by kinsey at 3:22 AM on December 18, 2019


This is an awesome question. Pretty sure this is not the answer, but I know when I strain to hear something, I inadvertently tighten whatever muscle it is between my eyes just above my nose.
posted by Mchelly at 7:49 AM on December 18, 2019


I'm an audiologist and I primarily study perception of noisy places by people with hearing loss.

Biogeo above has some of the right ideas, but I disagree on a couple points.

There is a difference between straining to detect a soft noise in quiet and straining to discriminate sounds in the presence of other sounds. The prior is driven almost entirely by listening effort, which is a sort of poorly understood construct of how hard to have to listen to make something out no matter what the conditions. It's similar to "cognitive load" in human factors engineering or general executive function load in neuropsych. There's a lot of debate as to what it actually *is* and how we ought to measure it.

Focusing on one sound in the presence of others is a more complicated story.

Indeed, focusing your attention on a sound amidst competing noises is (in audiology) called the cocktail party effect, originally coined way back in the day by Cherry. But it has come to be known as the general phenomenon where you can focus your attention on a single sound in the presence of background sounds.

How we are able to do this is one of the most complicated topics in hearing science, and in fact entire conferences and textbooks are dedicated to it. And we also don't fully understand how.

The actual ability to focus in on the sound is almost certainly driven primarily by top-down processes, primarily auditory attention. BUT, a whole slew of executive functions contribute to how well we can do this, like working memory, processing speed, inhibitory control. Basically, the better cognitive function you have generally, that is, the better able you are to focus and store short term information, the better you are at doing this.

But, there are a lot of environmental factors as well. They type of noise matters, whether you are getting the same background noise to each ear matters. For example, we are better able to do this when the background noise is presented to both ears equally but the signal of interest only to one ear, as opposed to noise to one ear and signal to one ear, or both in the same ear. Further, what type of noise matters. For example, most people are better able to do this when the noise is talker babble noise rather than a broadband white-type noise, because of an ability to listen in small gaps in the noise. So no matter how much we focus, we are limited by the type and orientation of the noise and signal.

Then, there are a bunch of other psychological aspects that play into how well we can do this. For example, how well we know the talker contributes to how well we can focus in one what they are saying amidst background noise. Mood, fatigue, semantic and linguistic content also all play a role. There's also a large body of literature examining whether this ability can be learned; for example, musicians sometimes demonstrate improved abilities to do this.

Finally, of course bottom-up processing matters as well, but much of this is out of our active cognitive control. To be sure, healthy outer hair cells, as found in a person with healthy, normal hearing, contribute extensively to our ability to do this, but not so much in terms of making the signal audible. It is true that outer hair cells have active processes that contribute to low hearing thresholds by "amplifying" the level of very quiet sounds, but in the case of hearing speech in noise, the much bigger contributors are outer hair cells providing: 1) very high frequency audibility not usually necessary for good speech perception in quiet; 2) very good temporal resolution necessary to perceive very fast elements of speech and listen in the noise dips; 3) good spectral resolution, so that many frequencies of the signal are filtered by the ear and provide the brain robust and redundant information.

These bottom-up processes are not typically considered to be under cognitive control. That said, there is some top-down manipulation of them, as outer hair cells are active. Again, this activation is probably not high-level in the sense that when we strain to hear we are consciously manipulating this process. It is more likely that this activation is coming from lower-level auditory centers in the brainstem and mid-brain. This is still a very active area of auditory research.

The tensor tympani muscle and the auditory reflex more generally have probably nothing to do with this. First, because it is a true reflex, although some individuals are able to flex it on consciously. The purpose of this reflex is unknown. It may be vestigial. It can reduce transmission of loud sounds to the ear by a few dB, but it decays really quickly and is not really a protective mechanism for all intents and purposes, at least anymore. Certainly it does nothing for speech in noise perception, for physics reasons I won't go into here.

There is some thought that a different reflex, the medial olivocochlear reflex, which projects from the superior olivary complex to the auditory nerve, might play a role in mediating the active outer hair cell mechanism during speech in noise perception, and which is low-level but still, to a certain degree, top-down, though not conscious. Again, this is an emerging topic.

There is an immense literature on this topic. This book is a good technical introduction.

tl;dr: this is an incredibly complex topic, one in which we both know a ton and we don't know much about, and one that has fascinated and continues to fascinate many stoned and sober scientists alike.
posted by Lutoslawski at 10:00 AM on December 18, 2019 [20 favorites]


> tilt my head

I'll just note that tilting and turning your head, even slightly, is one way to help with locating sounds in space.

Your auditory system uses a variety of cues to determine where the sounds are located in space, and in some cases they are ambiguous. For example, loudness difference and phase difference can't differentiate among sounds, say, directly in front of you and directly in back.

But move your head 3 or 4 degrees and you can.

So turning or tilting your head a bit is a little like the auditory equivalent of looking around.
posted by flug at 11:02 AM on December 18, 2019


I think my link to that book above doesn’t work because I was on campus and it links to a log in page. The book is “The Auditory System at the Cocktail Party”, from Springer.

coincidentally, as this is often called the cocktail party problem, I typically host a Speech in Noise themed party every year called the Cocktail Party Solution and you are all invited if you find yourself in Iowa
posted by Lutoslawski at 12:33 PM on December 18, 2019 [4 favorites]


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