How Our Hearing Works

How our Hearing Works

Your ears capture sound traveling through the air as vibrations in air pressure. The outer part of your ear (pinna) catches the sound waves first. The structure of your outer ear bounce sounds in different patterns depending on whether they come from behind you, above you or below you.piano_frequency_chart

Your brain learns to recognize these distinctive patterns to alert you, first, where a sound is coming from. Your brain can also determine whether the sound is coming from the left or right depending on which ear it arrives at first. As noted by How Stuff Works:1

Many mammals, such as dogs, have large, movable pinnae that let them focus on sounds from a particular direction. Human pinnae are not so adept at focusing on sound. They lay fairly flat against the head and don’t have the necessary muscles for significant movement.

But you can easily supplement your natural outer ear (pinnae) by cupping your hands behind your ears. By doing this, you create a larger surface area that can capture sound waves better.”

Your Fascinating Eardrum

Once sound waves pass your outer ear, they enter your ear canal and transmit vibrations to your eardrum, a thin piece of skin that sits between the ear canal and your middle ear and is connected to 3 very small bones which transmit the vibrations to the Inner ear.  

Your eardrum vibrates faster from high-pitch sounds while loud sounds move your eardrum back-and-forth a greater distance. But it’s far from simply a passive part of the hearing process.

When your eardrum detects prolonged exposure to loud noises, for instance, a reflex occurs that makes your eardrum more rigid, meaning it essentially dampens the noise to protect your hearing.

Loud, vs high tones

This same reflex kicks in when you’re having a conversation in a noisy room, helping you to hear higher-pitched sounds while making the lower-pitched ones. The reflex also occurs when you speak so that the sound of your own voice doesn’t overtake all the other sounds around you.2

Once sound waves vibrate your eardrum, it moves a group of tiny bones in your middle ear called the malleus, the incus, and the stapes. (2nd photo above, red, blue and yellow bones)

Collectively known as the ossicles, these are the smallest bones in your body, but they have a very important job – amplifying the force from your eardrum so the sound information can be passed on to your inner ear.

Sound in Your Inner Ear

The amplified vibrations from your eardrum travel to the cochlea in your inner ear, which conducts sound through fluid (instead of through air, as it done in your outer ear). It’s here that the sounds are translated into nerve impulses that your brain can recognize and understand as distinct sounds. According to How Stuff Works:3

“The cochlea structure consists of three adjacent tubes separated from each other by sensitive membranes… The stapes moves back and forth, creating pressure waves in the entire cochlea.

The round window membrane separating the cochlea from the middle ear gives the fluid somewhere to go. It moves out when the stapes pushes in and moves in when the stapes pulls out.

The middle membrane, the basilar membrane, is a rigid surface that extends across the length of the cochlea. When the stapes moves in and out, it pushes and pulls on the part of the basilar membrane just below the oval window.

This force starts a wave moving along the surface of the membrane. The wave travels something like ripples along the surface of a pond, moving from the oval window down to the other end of the cochlea.

The basilar membrane has a peculiar structure. It’s made of 20,000 to 30,000 reed-like fibers that extend across the width of the cochlea. Near the oval window, the fibers are short and stiff. As you move toward the other end of the tubes, the fibers get longer and more limber.

This gives the fibers different resonant frequencies… Because of the increasing length and decreasing rigidity of the fibers, higher-frequency waves vibrate the fibers closer to the oval window, and lower frequency waves vibrate the fibers at the other end of the membrane.”

Your Brain Does the Final Interpreting 

When a wave reaches fibers with a resonant frequency, it releases a burst of energy that then moves tiny hair cells found in the organ of corti, a structure that stretches across the length of the cochlea.

The movement from the hair cells sends an electrical impulse through the cochlear nerve, which in turn transmits the information to the cerebral cortex in your brain for interpretation. Yet, even with all that is known about hearing, there is much yet to be discovered. How Stuff Works reported:

“The cochlea only sends raw data – complex patterns of electrical impulses. The brain is like a central computer, taking this input and making some sense of it all. This is an extraordinarily complex operation, and scientists are still a long way from understanding everything about it.

In fact, hearing in general is still very mysterious to us. The basic concepts at work in human and animal ears are fairly simple, but the specific structures are extremely complex. Scientists are making rapid advancements, however, and they discover new hearing elements every year.

It’s astonishing how much is involved in the hearing process, and it’s even more amazing that all these processes take place in such a small area of the body.”

Why It’s Important to Protect Your Ears from Excessive Noise

Your ears are designed to take in sounds, and the eardrum even has some built-in protections against excessively loud prolonged noises. However, exposure to excessive noise can still be damaging to your health and hearing. In the US it’s estimated that 100 million people are exposed to unhealthy levels of noise, typically from automobile and aircraft traffic (although everything from leaf blowers and lawnmowers to loud music can also contribute).

Noise pollution may increase your risk of hearing loss, but it goes much further than that. Stress, sleep disturbances, diminished productivity, and even heart disease can also result.

loss chart 2

One of the key ways excessive noise harms your heart is by elevating stress hormones such as cortisol, adrenaline, and noradrenaline, which, over time, can lead to high blood pressure, stroke, and heart failure.

One review of research showed that “arousal associated with nighttime noise exposure increased blood and saliva concentrations of these hormones even during sleep.” And according to research published in Environmental Health Perspectives, long-term exposure to traffic noise may account for approximately 3 percent of coronary heart disease deaths (or about 210,000 deaths) in Europe each year.

Research also suggests long-term exposure to noise pollution may have an affect on cognitive development in children and cognitive and psychological functions in adults, although more research is needed in this area.8 One study of traffic wardens in Pakistan found significant physio-psychological effects due to traffic noise pollution, including:

Aggravated depression: 58% Stress: 65% Public conflict: 71%
Irritation and annoyance: 54% Behavioral affects: 59% Speech interference: 56%.
Hypertension: 87% Muscle tension: 64% Exhaustion: 48%
Low performance levels: 55% Concentration loss: 93% Hearing impairment: 69%
Headache: 74% Cardiovascular issue: 71%  

What’s the Best Way to Protect Your Hearing?

Minimizing your exposure to excessive noise is important. If you live in a very noisy area, such as near a highway or airport, you may want to consider moving. If that is not an option, consider adding acoustical tile to your ceiling and walls to buffer the noise. Double-paneled windows and insulation can also help. At the very least, you can sound-treat your home by adding heavy curtains to your windows, rugs to your floors, and sealing air leaks. If noise is only an issue occasionally, sound-blocking headphones can eliminate such disturbances.

If noise is an issue during the night, you may want to consider adding pink noise to your bedroom. Pink noise is steady with a consistent frequency, like the sound of wind or constant rain. Research shows that steady pink noise can help slow down and regulate your brainwaves for more stable sleep and improved sleep quality.  While pink noise CDs are available, you can also simply turn on a fan in your bedroom to block out noise disturbances and instead take advantage of this beneficial type of pink noise.

If you work in a noisy environment, be sure you are wearing ear protection at all times, and leave the site as often as possible, such as during breaks and lunch. Also be cognizant of noise exposures during your leisure time, such as that from motorcycles, lawnmowers, leaf blowers, and even loud music and television. Wear ear protection when using your lawnmower, for instance, and try to make less noise when you can, not only for your own sake but also for the sake of those around you.

If You’re Having Trouble Hearing, It Could Be Due to a Buildup of THIS…

Partial loss of hearing, a sensation your ears are plugged, or a feeling of fullness in your ears can all be indicative of an excess of earwax buildup that needs attention. To be clear, earwax is a substance that’s meant to be in your ears. It aids in your ears’ self-cleaning process, providing protection, lubrication, and antibacterial properties.

In most cases, your ear canals should not have to be cleaned out (with a cotton swab or otherwise), as they’re a self-cleaning part of your body. Excess earwax should move out of your ear canal automatically, as cells there actually migrate naturally. The removal of earwax is also helped along by movements of your jaw (talking, chewing, etc.), and once it reaches your outer ear it will simply fall out or be removed when you shower or bathe.

Using a cotton swab to clean your ears can actually push earwax deep into your ear where it doesn’t belong, blocking your ear canal, and leading to hearing loss. But, if you have the symptoms mentioned above, earwax buildup could be to blame. In one study, when impacted earwax was removed in the elderly, hearing improved significantly, as did the participants’ cognitive function (which was being affected by their lessened hearing).  An ear, nose, and throat (ENT) doctor, or otolaryngologist, can remove earwax using a special suction, miniature instruments and a microscope.

If your eardrum is perforated, manual removal by a physician is recommended, however in most other cases you can clear earwax blockages at home.

The simplest way to do this is to first soften the wax by placing a few drops of olive oil, coconut oil, or water in your ear. Then, pour a capful of 3 percent hydrogen peroxide in each ear to flush the wax out. It’s worth noting that using plain sterile water, or a sterile saline solution, to soften earwax works just as well as oil or over-the-counter ear drops. You will also want to be sure to increase your intake of omega-3 fats, as frequent excess buildup of earwax can oftentimes be traced back to an omega-3 deficiency Sources and Reference

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