Needless to say, establishing the cause of hearing loss can be complex. Further complicating the situation is the fact that few individuals are aware that their hearing is diminishing. Many first notice the problem when family members warn that the TV is turned up too loudly, or when someone at the office points out that the phone is ringing. It is not at all unusual for others to first draw attention to hearing problems. It seldom occurs suddenly.
Deterioration proceeds unconsciously, little by little.
As sound occurs in wave motions, it is measured in frequencies, or the number of vibrations per second. The hearing capacity is usually expressed as hearing level. A hearing level of 0 dB is equivalent to a sound pressure level of 4 dB. Figure 1 shows relative levels of sound pressure when the frequency for each sound is 1,000 Hz. The greater the number value, the louder the sound. Usually, healthy ears can recognize from 4 to 130 dB in sound pressure level.