The sense of hearing and the ear is an elegantly complex mechanism allowing humans to perceive waves of pressure in the air as intelligible sounds. The intricate workings of this sense organ are delicately sensitive yet durable. With aging, most adults experience some loss of hearing or other related issues for a variety of reasons. Understanding the causes of hearing loss varies from simple to quite complex. Exposure to extremely loud working conditions without proper hearing protection is a commonsense cause. On the other hand, understanding pulsatile tinnitus requires a more comprehensive familiarity with the anatomy of the human ear.
Sources of sound vary dramatically from the sweet high notes on a violin to the loud crashing of ice calving off a glacier. The sounds themselves are all transmitted in the same way. A sound is transferred through distance as waves of varying pressure in a medium such as air. A bow is drawn across a violin string causing the string to vibrate. The body of the violin is designed to amplify those vibrations in the air around it. As these waves travel over an unobstructed distance, they retain their shape well, but lose a small amount of energy as they dissipate.
Hearing a sound is a process of decoding the sound waves and converting their mechanical energy into electrochemical nerve impulses. Accomplishing this task is the main function of the ear.
The Eardrum or Tympanic Membrane
The first thing a sound wave encounters within an ear is the eardrum. This is a membrane that covers an approximate area of 63 square millimeters. It is a thin piece of tissue that is taut and roughly oval. As the name implies, not too dissimilar from a drumhead.
The Middle Ear
The eardrum or tympanic membrane separates the outer from the middle ear. The middle ear consists of three tiny bones known as the malleus, incus and stapes or, more commonly, the hammer, anvil and stirrup respectively. Attached to the inside of the eardrum is the malleus or the handle portion of the “hammer”. Sound waves cause the eardrum to vibrate and these vibrations are transmitted mechanically to the three bones of the middle ear.
The Inner Ear
Three sense organs exist within the inner ear. Only one of these is concerned with the sense of hearing. The other two are the organs of balance and equilibrium. The hearing mechanism is known as the cochlea, a spiral snail shell-shaped organ. Although not fully understood even today, inside the cochlea, two subdivisions or channels are separated by a membrane. Within these channels, flooded with different fluids are specialized cells and hair-like neurons with unique characteristics that allow them to generate electrochemical impulses in proportion to the physical sound wave energy imparted.
Pulsatile tinnitus is caused by the arteries and veins near these sensitive organs. A common symptom is hearing a steady rhythmic pulsing sound that is synchronous with the heartbeat. This is a form of objective tinnitus meaning a doctor can also hear the sound when listening with a stethoscope. The condition may be indicative of other underlying health concerns such as high blood pressure or problems with arteries and veins. Other symptoms may affect equilibrium and even vision. Consultation with a physician specializing in hearing conditions is recommended to identify and determine an appropriate course of treatment.