Deafening Trivia Quiz

Answer: Hair cells

Hair cells reside in a part of the cochlea called the organ of Corti and are mechanosensory cells that convert physical stimuli into electrical stimuli. The cochlea is a fluid filled organ and the frequency and amplitude of the sound wave determine which hair cell is activated.

In mammals, there are actually two types of hair cells. There is a more abundant outer hair cell that amplifies the sound and a more sensitive inner hair cell that actually triggers the action potential to the auditory nerve. Hair cells are tiny and unfortunately do not regrow in humans, so as they get damaged the loss in hearing is permanent.

Answer: A sensitive human ear cannot hear below 10 dB

Some humans can actually hear a little below 0 dB! The decibel scale is a bit unusual as it is a ratio rather than a unitary measurement of force. When the decibel scale was first developed, one decibel was the smallest increase in sound that is detectable by the human ear. Also when Alexander Graham Bell and other scientists started measuring sound, they decided to set 0 dB to be approximately the lowest level of sound a healthy human ear could detect based on experiments at the time. The range of sound waves that a human can hear is huge and one of the reasons why the decibel scale is logarithmic. With the base 10 logarithmic scale, a change of 3 decibels is approximately double the force in the sound wave.

You may also be wondering why it is a decibel and not just a bel. The original unit of a bel was a measurement of how much power was lost over 1 mile of a telephone or telegraph cable. The human ear however, can differentiate about 1 tenth of a bel which made the decibel more useful. To add to the confusion, there are several different decibel scales and even one to measure light since human sensitivity to light is also on a logarithmic scale.

Answer: The pitch of the sound

The pitch of a sound does not cause hearing loss. However, it is common for a person with hearing loss to struggle to hear higher pitched sounds. This is because the hair cells which are responsible for detecting higher pitched sounds are in a position where they can more easily get damaged by forceful sound waves. So the sound factors that can contribute to hearing loss are related to how powerful (loud) the sound wave is when it reaches the ear. Since the strength of the sound wave decreases over distance, being closer to the source of a sound would result in that sound being louder.

The second factor is the amount of time the ear is exposed to the sound. Prolonged exposure to a loud enough sound can lead to irreversible damage. The full consequence of the damage does not always appear until many years later. So, unfortunately, a person may not always realize the harm that is being caused by excessive sound exposure.

Answer: About 7 seconds

As scary as it sounds, it only takes about 7 seconds to cause hearing damage to the ears at a typical rock concert played at 120 dB! To make matters worse, the damage does not appear right away and often can take years to become evident. And, as you guessed, the damage is permanent. Various forms of hearing protection can be used to reduce the amount of loudness that reaches the sensitive ears but, of course, these protective measures also muffle the sound quality which makes them unpopular. Loud music can sound amazing, but it comes at a high cost.

Answer: Continuing to hear a sound for a brief moment even after the source has stopped

For a brief time after a sound stops the inner ear experiences a short after-vibration which is normal and can occur at a safe sound level. Understanding just when a sound becomes damaging can be rather tricky. Here's a tip: when a sound gets up to about 85 dB, someone is sitting next to you would have to raise their voice so you could hear them over the 85 dB sound.

The average human voice is usually measured at about 60 dB. Other clear signs that the ears have been damaged by a sound include hearing muffled speech and experiencing ringing in the ears after a loud sound stops.

While these effects will often go away within a few hours to days, this does not mean the ears are back to normal. Tinnitus (ringing in the ears) can be permanent and often becomes most noticeable when in the quietest setting.

Answer: False

Unfortunately, the total reduction in sound is not that easy to calculate. One challenge is the frequency of the sound can be a factor in the canceling effects of the earplugs. Most earplugs more easily cancel out higher frequency sounds than lower frequency sounds making them less effective at those lower frequencies.

In order to rate the safety of an earplug for all ranges of sounds, a little math has to be applied to the NRR rating. The formula that is typically used is to take the NRR and subtract 7 and then divide by 2. So if an earplug offers an NRR of 30, you would subtract 7 to get 23 and then divide by 2 to end up with an 11.5 dB reduction.

Therefore, earplugs with an NRR rating of 30 would reduce a 110 dB sound to about 98.5 dB for all frequencies of sounds.

The higher frequency sounds would be reduced more which is why the higher frequencies sounds are more muffled. One other factor when considering hearing protection is it must be used correctly to provide the stated benefits.

It is important to follow the directions provided by the manufacturer to gain the best protection.

Answer: Ruptured eardrum

While not too common, ear infections can get bad enough that the eardrum ruptures, possibly resulting in a bloody, watery discharge. While ear infections often cause pain and are treated with antibiotics before they get bad enough to rupture the eardrum, it is possible for there not to be much pain until the infection is well advanced. Usually, the prognosis is good since the eardrum can heal minor ruptures on its own within a few weeks. Occasionally, the doctor will need to put a special small paper patch on the eardrum to help it heal.

When a person has frequent chronic ear infections the doctor may recommend putting in ear tubes to reduce the frequency of infection.

Answer: Sound therapy to retrain the ear

Hyperacusis can happen after a head injury, post traumatic stress, or Lyme disease to name a few. While normal sounds are louder and can be painful, the sufferer does not have increased hearing. Rather, hyperacusis is the brain's interpretation of sound being too loud.

A common treatment for patients with hyperacusis is reconditioning sound therapy. The goal is to retrain the brain to tolerate the sounds and eventually not be as bothered by them. While patients with hyperacusis may wear ear protection to make everyday life more bearable, the ear protection can actually make the condition worse and make the ears even more sensitive to sounds. Tinnitus is often common in patients with hyperacusis. Psychotherapy can also sometimes be of benefit to a sufferer.

Answer: A translator

A translator is not a part of a basic hearing aid. People who benefit from a hearing aid often lose the ability to hear quieter sounds due to hair cell loss. When a sound is loud enough they can hear it as the remaining hair cells do still work. So hearing aids simply make many sounds louder.

A standard hearing aid goes into the ear where the microphone picks up sounds from the environment. The aid then amplifies targeted ranges of sounds specific to the user's needs. Hearing aids do require that some of the hair cells can still function in order for the wearer to understand what they are hearing.

Unfortunately, many people who could benefit from a hearing aid do not wear them. For one, they can be very expensive. Others might not wear them because they can be uncomfortable or they may feel embarrassed to have others see them wearing one.

Answer: False

Cochlear implants bypass the damaged hair cells and directly stimulate the auditory nerves. Unfortunately, it takes time for the brain to learn how to interpret the signals provided by the implant and normal hearing is never completely restored. Cochlear implants are designed to help the wearer hear warning signs from their environment and be able to recognize speech, but it does take practice. So while a cochlear implant is an amazing tool for someone who is deaf or extremely hard of hearing, a hearing aid is still the best option for someone whose ears are still able to hear. Maybe one day cochlear implants will be good enough to help the brain recognize sound like a healthy ear.