![\"Balancing_Act_01_DK_Box_SM_AMEND\"](\"https:\/\/healthyaging.net\/magazine\/wp-content\/uploads\/2016\/10\/Balancing_Act_01_DK_Box_SM_AMEND-750w.jpg\")
How the brain hears<\/h4>\n
Once signals from the ear reach the brain, complex processing is needed to extract information. Our brains determine what the sound is, where it is coming from, and how we feel about it. The brain is able to focus in on one sound over another, and even tune out unnecessary noises completely.<\/p>\n
Localizing sound<\/h4>\n
We use three main cues to find the location of a sound source\u2014its loudness, its frequency pattern, and the difference in arrival time at each ear. We use frequency pattern to tell if the sound is in front or behind us, because our ear\u2019s shape means that a sound coming from in front has a different pattern of frequencies than the same sound coming from behind.<\/p>\n
Our ears don\u2019t help much in pinning down the height of sound sources, though. Left and right localization is easier\u2014a sound from the left is louder in the left ear than in the right, particularly at high frequencies. It also reaches our left ear a few milliseconds before our right. The diagrams on the right show how the brain uses this information.<\/p>\n
Tuned in<\/h4>\n
Our brains can \u201ctune in\u201d to a single conversation over the babble of noise at a party by grouping sounds into separate streams, based on frequency, timber, or source. It might seem as though you don\u2019t hear any of the other conversations\u2014but you will notice if someone mentions your name. That\u2019s because your ears still send signals from the other conversations to the brain, which will override the filtering if something important comes up elsewhere.<\/p>\n
Why does music make us emotional?<\/h4>\n
Music can cause strong emotional reactions\u2014whether it\u2019s the soundtrack heightening fear in a scary movie, or chills created by a haunting melody. We know there are a wide range of brain areas involved in the emotions elicited, but we don\u2019t know why or how music creates such dramatic feelings in the listener, or why the same song affects people differently.<\/p>\n
Why do we stand still to listen?<\/h4>\n
It is easier to listen carefully when we stop moving altogether. This helps us hear better by stopping sounds that are generated by our own movements.<\/p>\n
Finding the Source<\/h4>\n
Different neurons are activated depending on the delay between a sound first reaching the nearer ear and then reaching the farther ear. This tells us what direction the sound comes from.<\/p>\n
Cone of confusion<\/h4>\n
In a cone-shaped region outside each ear, signals are ambiguous and we find it difficult to localize sounds. Tilting or swiveling our heads can move the sound source out of this confusing region and help us locate the sound.<\/p>\n
Balancing act<\/h4>\n
As well as hearing, our ears are responsible for keeping our balance and telling us how and in which direction we are moving. They do this using a set of organs in the inner ear\u2014one on each side of the head.<\/p>\n
Turning and movement<\/h4>\n
Inside each of our ears, three fluid-filled canals sit at roughly 90 degrees to each other. One responds to motions such as forward rolls, the second to cartwheels, and the third to pirouettes. The relative motion of the fluid tells our brains in what direction we are moving. When spinning repeatedly in the same direction, the fluid builds up momentum. Once that matches the rate of spin, it stops deflecting the hair cells and you no longer feel motion. After you stop, however, the liquid continues, giving the feeling that you are still moving, known as dizziness.<\/p>\n
Why does alcohol make your head spin?<\/h4>\n
Alcohol builds up quickly in the cupulas of the inner ear and makes them float in their\ncanals. When you lie down, the cupulas are disturbed and the brain thinks you are spinning.<\/p>\n
Turning sense organs<\/h4>\n
When you move, the liquid inside the canals moves, too, but because it has inertia, it takes a while to start moving. This movement displaces a gelatinous mass called the cupula, disturbing the hair cells inside it and sending signals to the brain. When the cupula is bent in one direction, the nerves increase their rate of firing. If it is bent in the other direction, firing is inhibited\u2014this tells the brain the direction of the motion.<\/p>\n
Steady gaze<\/h4>\n
Your brain constantly adjusts the tiny movements your muscles make to keep you balanced. Inputs from the eyes and muscles combine with those from your inner ear to determine which way up you are.<\/p>\n
Ballet dancers\u2019 brains adapt to suppress the sensation of dizziness after spinning.<\/p>\n
Correction reflex<\/h4>\n
Our eyes automatically correct for head movements, keeping the image on our retina stationary. Without this reflex, we would be unable to read, as the words would jump about every time our head moved.<\/p>\n
Gravity and acceleration<\/h4>\n
As well as turning motions, our inner ears sense straight-line acceleration\u2014backward and forward, or up and down. We have two organs to sense acceleration\u2014 the utricle is sensitive to horizontal movements while the saccule detects vertical acceleration (such as the movement of an elevator). Both organs sense the direction of gravity relative to the head, such as when the head is tilted or level.<\/p>\n
Gravity sense organs<\/h4>\n
The hair cells in the utricle and saccule are within a gelatinous layer, topped with a structure containing tiny stones. Due to the weight of the structure, gravity moves it when the head is tilted, which in turn deflects the hairs. During acceleration, the stone-filled layer takes longer to start moving because of its greater mass. If there are no other cues, it can be hard to tell the difference between a head tilt and acceleration.<\/p>\n
![\"Hearing_problems\"](\"https:\/\/healthyaging.net\/magazine\/wp-content\/uploads\/2016\/10\/Hearing_problems-750.jpg\")
Hearing problems<\/h4>\n
Deafness and hearing problems are common but often treatable thanks to technological advances. Most people develop some form of hearing loss as they age due to damage to the components of the inner ear.<\/p>\n
Causes of hearing problems<\/h4>\n
Deafness from birth is usually caused by genetic mutations that stop the ear from working properly. The hearing problems shown here can occur as a result of injury or illness throughout life.<\/p>\n
Blocked pathways<\/h4>\n
The ear converts sound waves in the air into nerve signals our brain can interpret. Anything that stops this process from working, such as a physical blockage or damage, can cause hearing problems.<\/p>\n
How loud is too loud?<\/h4>\n
The decibel sound scale is logarithmic, and every 6 dB increase in volume doubles the sound energy. Loud noises can damage hair cells and above a certain level of damage the cells can\u2019t repair themselves and die. If enough hair cells die, you can lose the ability to detect certain frequencies.<\/p>\n
Around age 18, you begin losing the ability to hear very high-pitched noises.<\/p>\n
Why do loud noises make your ears ring?<\/h4>\n
Loud noises vibrate hair cells so violently that the tips can snap off, causing them to send signals to your brain after the noise has finished. The tips can grow back within 24 hours.<\/p>\n
![\"COCHLEA_IMPLANT4\"](\"https:\/\/healthyaging.net\/magazine\/wp-content\/uploads\/2016\/10\/COCHLEA_IMPLANT4-750w.jpg\")
Cochlear implants<\/h4>\n
Normal hearing aids simply amplify sounds and cannot help people with damaged or missing hair cells. Cochlear implants replace the function of the hair cells, converting sound vibrations into nerve signals that the brain learns to interpret. Increased current through the electrodes within the cochlea produces a louder sound, while the position of the activated electrodes determines pitch.<\/p>\n
How they work<\/h4>\n
External microphones detect sounds and send them to the processor. Signals then travel to the internal receiver via the transmitter, before passing as electric current to the electrode array inside the cochlea. Stimulated nerve endings send signals to the brain and sounds are heard.<\/p>\n
The brain has cells that respond only to some frequencies, just like the different parts of the cochlea in the inner ear.<\/p>\n
To learn more about how your body functions, the book, How the Body Works<\/em>, has excellent answers.<\/p>\n Taking some of the mystery out of how our bodies function<\/p>\n","protected":false},"author":3,"featured_media":4538,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[62,64],"tags":[],"class_list":["post-4288","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fall-2016","category-fall-2016-features"],"acf":[],"_links":{"self":[{"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/posts\/4288","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/comments?post=4288"}],"version-history":[{"count":5,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/posts\/4288\/revisions"}],"predecessor-version":[{"id":4545,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/posts\/4288\/revisions\/4545"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/media\/4538"}],"wp:attachment":[{"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/media?parent=4288"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/categories?post=4288"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/healthyaging.net\/magazine\/wp-json\/wp\/v2\/tags?post=4288"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Text and Images reproduced by permission of DK, a division of Penguin Random House from\u202fHow the Body Works<\/em> \u00a92016 by DK. All rights reserved.<\/h5>\n","protected":false},"excerpt":{"rendered":"