The human ear is the envy of even the most sophisticated acoustic engineer. Without a moment's thought or the slightest pause, you can hear the difference between a violin and a clarinet, you can tell if a sound is coming from your left or your right, and if it's distant or near. And you can discriminate between words as similar ashearandnear,soundandpound.

Nearly everyone experiences trouble hearing from time to time. Common causes include a buildup of earwax or fluid in the ear, ear infections, or the change in air pressure when taking off in an airplane. A mild degree of permanent hearing loss is an inevitable part of the aging process. Unfortunately, major hearing loss that makes communication difficult also becomes more common with increasing age, particularly after age 65.

Testing — 1, 2, 3

How do you know if you need a hearing test? If you answer yes to any of the questions below, talk with your doctor about having your hearing tested:

  • Are you always turning up the volume on your TV or radio?
  • Do you shy away from social situations or meeting new people because you're worried about understanding them?
  • Do you get confused or feel "out of it" at restaurants or dinner parties?
  • Do you ask people to repeat themselves?
  • Do you miss telephone calls — or have trouble hearing on the phone when you do pick up the receiver?
  • Do the people in your world complain that you never listen to them (even when you're really trying)?

You can also ask a friend to test you by whispering a series of words or numbers. After all this, if you think you have a hearing problem, you should have a test.

What does a hearing test involve?

Thorough hearing evaluations start with a medical history and examination of your ears, nose, and throat, followed by a few simple office hearing tests. An audiogram is the next step.

For an audiogram, you sit in a soundproof booth wearing earphones that allow each ear to be tested separately. A series of tones at various frequencies are piped to your ear. An audiologist will ask you to indicate the softest tone you can hear in the low-, mid-, and high-frequency ranges.

People with excellent hearing can generally hear tones as soft as 20 decibels (dB) or less.

If you can't hear sounds softer than 45 to 60 dB, you have moderate hearing loss, and if you don't hear sound until it's ramped up to 76 to 90 dB, you have severe hearing loss.

Hearing tones is nice, but hearing and understanding words is crucial too.

For this reason, the audiologist will also play tape-recorded words at various volumes to find your speech reception threshold, or the lowest dB level at which you can hear and repeat half of the words. Finally, you'll be tested with a series of similar sounding words to evaluate your speech discrimination.

For more on diagnosing and treating hearing loss, buy Hearing Loss, a Special Health Report from Harvard Medical School.