How We Hear

Sources of Sound
When we “hear” sound, our ears are picking up air movement from either a vibrating object (like a violin string) or a rushing stream of air (like a flute or human voice). Sounds are able to reach our ears because it travels along a medium that “carries” vibrations. The medium that we are most familiar with is air. Sound vibrations can also travel through other mediums as well, such as water or steel.

Why is Noise, Noise?
Noise is an unwanted sound that creates a disturbance in the frequency range of interest. For example, if you are engaged in conversation (your frequency range of interest) and a train whistle blows, the whistle interferes with your conversation and is therefore considered noise.

One of the most common disturbances for hearing instrument users is the presence of background noise in restaurants, cars, and in the workplace.

Why Are Loud Sounds, Loud?
Loudness is an impression we get about a sound’s strength through changes in pressure that we feel in our ears. The stronger the pressure, the louder we perceive the sound to be. When we talk about loudness, we use the term decibel (dB).

Sensitivity of the Ear
The range of normal human hearing is so sensitive we can detect the whisper of a dry leaf in a tree overhead (20 dB), yet so flexible that we can tolerate the sound of a jet plane taking off (80 dB). At any age and for many different reasons our hearing sensitivity can begin to change, making communication increasingly difficult. Sounds in the environment, especially speech sounds that were once perceived as loud enough to hear easily, may no longer be perceived as sufficiently loud to allow for easy communication.