These ghost sounds can be distracting and annoying. In fact, bent or broken hair cells will be leaking an electrical signal that the brain will misread as sound. It can appear to come from one ear or both. Tinnitus can occur continuously or just now and again. Called tinnitus (TIN-ih-tus), these are ringing, buzzing, clicking, hissing or roaring sounds. Sometimes, before that selective hearing loss starts to occur, people will develop ghost sounds. Some words or high-pitched speakers may be hard to interpret. CDC/ National Institute for Occupational Safety and HealthĪs hair cells that are sensitive to high-pitch die off, people may have a hard time understanding their environment. Sounds in the 4000 to 6000 hertz range now must be many decibels louder for that person to hear. And by 55, that carpenter (red line at right) can be seriously compromised. The data shown on this graph illustrate how noise pollution associated with tools can reduce the hearing of a 25-year old carpenter (upper dotted line) to that typical of a healthy person twice his age (lower dotted line). Hearing tends to fall off somewhat with age. A single gunshot near unprotected ears can cause permanent damage. But if the sounds are loud enough - and especially if they come without warning - they might do real damage. This can cause a temporary deafness, or perhaps only an inability to hear high-pitched sounds. The damage noise can causeĪs hair cells in the tiny cochlea become bombarded by loud sounds, they can become damaged and fail to work. For very short percussive sounds - thunder, a gunshot or a firecracker - the sound may enter and do its damage before the ear has had time to turn on this semi-protective reflex. Moreover, it takes a few hundredths of a second for the brain to realize this reflex is needed before it goes into effect. The problem is, it can’t prevent all sound from entering. This action is known as the acoustic reflex. Just as the eyelid tends to close in bright light, to shield the eye, muscles in the ear can try to shut off the entryway to shield inner tissues from overly loud sounds. So an early sign of noise-induced hearing loss can be an inability to hear high-pitched sounds. Hair cells that respond to high-pitched sounds tend to die off first. So, as hair cells die off, people lose their ability to detect sounds. Loud sounds can damage them - or kill them altogether. Their movements send messages to the brain that will register the sound of various pitches. They contain bundles of tiny hair-like strands that wave back and forth in response to sounds. Ossicles - the three tiniest bones in the body - transmit sounds to a fluid-filled snail-shaped structure. It collects sound and funnels it through a series of structures to the inner ear. The outer ear is shaped a bit like a horn. That’s the decibel levels, or what we think of as how loud sounds are. But in terms of health, the more important feature is its energy. This tends to be high, like a bird’s tweet, low like a tuba or somewhere in between. Sounds cause these hairs to vibrate, sending out impulses that the brain will recognize as sound. These aspects of the wave cause whatever a sound hits to vibrate.Īn electron micrograph shows one of the ear’s tiny hair-like bundles within a hair cell. The stretching back out of the wave pulls on the tissue. The compression exerts a push on things, such as ear tissue. Sound travels through the air in waves that compress, stretch and then repeat. The deck of a Navy carrier can hit 140 decibels as a jet takes off. A music club or jet takeoff from a distance of 610 meters (2,000 feet) can bombard the ears at 120 decibels. Passing trains and thunder may register 100 decibels. Moderate urban traffic can run 70 decibels. That is 10 billion times as intense (as measured in acoustic energy carried by sound waves) as just 1 decibel. And televisions, stereo equipment and headsets may expose a teen’s ears to sounds exceeding 100 decibels. A vacuum cleaner may let out an 80-decibel roar. When garbage disposals, mixers, blenders or dishwashers get going, noise levels can reach 80 or 90 decibels. Yet today, few people live in such quiet surroundings. With people whispering or shuffling through pages of a book, even a library may run 35 decibels. Outdoor traffic and bird calls can sometimes raise the sound level in bedrooms to 40 decibels. The human ear evolved to detect 10 decibel whispers and rustles in a quiet woodland - something that might warn of dangers. But sound levels can be so high that without protection, the music might damage a band’s fans. Earplugs may seem counterproductive when going to a concert.
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