Saylor URL: http://www.saylor.org/books Saylor.org
[13] Sekuler, R., & Blake, R., (2006). Perception (5th ed.). New York, NY: McGraw-Hill.
4.3 Hearing
LEARNING OBJECTIVES
- Draw a picture of the ear and label its key structures and functions, and describe the role they play in hearing.
- Describe the process of transduction in hearing.
Like vision and all the other senses, hearing begins with transduction. Sound waves that are
collected by our ears are converted into neural impulses, which are sent to the brain where they
are integrated with past experience and interpreted as the sounds we experience. The human ear
is sensitive to a wide range of sounds, ranging from the faint tick of a clock in a nearby room to
the roar of a rock band at a nightclub, and we have the ability to detect very small variations in
sound. But the ear is particularly sensitive to sounds in the same frequency as the human voice.
A mother can pick out her child’s voice from a host of others, and when we pick up the phone
we quickly recognize a familiar voice. In a fraction of a second, our auditory system receives the
sound waves, transmits them to the auditory cortex, compares them to stored knowledge of other
voices, and identifies the identity of the caller.
The Ear
Just as the eye detects light waves, the ear detects sound waves. Vibrating objects (such as the
human vocal chords or guitar strings) cause air molecules to bump into each other and produce
sound waves, which travel from their source as peaks and valleys much like the ripples that
expand outward when a stone is tossed into a pond. Unlike light waves, which can travel in a
vacuum, sound waves are carried within mediums such as air, water, or metal, and it is the
changes in pressure associated with these mediums that the ear detects.
As with light waves, we detect both the wavelength and the amplitude of sound waves.
The wavelength of the sound wave (known as f requency) is measured in terms of the number of
waves that arrive per second and determines our perception of pitch, the perceived frequency of a
sound. Longer sound waves have lower frequency and produce a lower pitch, whereas shorter
waves have higher frequency and a higher pitch.