Hockenbury Discovering Psychology 5th txtbk

102 CHAPTER 3 Sensation and PerceptionHigh-pitched, loud(high frequency,high amplitude)Low-pitched, soft(low frequency,low amplitude)Complex(high and lowfrequency,high and lowamplitude)(a)Frequency(b)(c)Figure 3.7 Characteristics of SoundWaves The length of a wave, its height,and its complexity determine the loudness,pitch, and timbre that we hear. The soundproduced by (a) would be high-pitchedand loud. The sound produced by (b)would be soft and low. The sound in (c) iscomplex, like the sounds we usually experiencein the natural world.auditionThe technical term for the sense of hearing.loudnessThe intensity (or amplitude) of a soundwave, measured in decibels.amplitudeThe intensity or amount of energy of awave, reflected in the height of the wave;the amplitude of a sound wave determinesa sound’s loudness.decibel(DESS-uh-bell) The unit of measurement forloudness.pitchThe relative highness or lowness of a sound,determined by the frequency of a soundwave.frequencyThe rate of vibration, or the number ofsound waves per second.timbre(TAM-ber) The distinctive quality of a sound,determined by the complexity of the soundwave.outer earThe part of the ear that collects soundwaves; consists of the pinna, the ear canal,and the eardrum.eardrumA tightly stretched membrane at the end ofthe ear canal that vibrates when hit bysound waves.middle earThe part of the ear that amplifies soundwaves; consists of three small bones: thehammer, the anvil, and the stirrup.AmplitudeThe sense of hearing, or audition, is capable of responding to a widerange of sounds, from faint to blaring, simple to complex, harmoniousto discordant. The ability to sense and perceive very subtle differencesin sound is important to physical survival, social interactions, and languagedevelopment. Most of the time, all of us are bathed in sound—so much so that moments of near-silence, like our experience in thedesert, can seem almost eerie.What We HearThe Nature of SoundWhether it’s the ear-splitting screech of metal on metal or the subtlewhir of a grasshopper’s wings, sound waves are the physical stimuli thatproduce our sensory experience of sound. Usually, sound waves areproduced by the rhythmic vibration of air molecules, but sound waves can be transmittedthrough other media, too, such as water. Our perception of sound is directlyrelated to the physical properties of sound waves (see Figure 3.7).One of the first things that we notice about a sound is how loud it is. Loudnessis determined by the intensity, or amplitude, of a sound wave and is measured inunits called decibels. Zero decibels represents the loudness of the softest sound thathumans can hear, or the absolute threshold for hearing. As decibels increase, perceivedloudness increases.Pitch refers to the relative “highness” or “lowness” of a sound. Pitch is determinedby the frequency of a sound wave. Frequency refers to the rate of vibration,or number of waves per second, and is measured in units called hertz.Hertz simply refers to the number of wave peaks per second. The faster the vibration,the higher the frequency, the closer together the waves are—and thehigher the tone produced. If you pluck the high E and the low E strings on aguitar, you’ll notice that the low E vibrates far fewer times per second than doesthe high E.Most of the sounds we experience do not consist of a single frequency but arecomplex, consisting of several sound-wave frequencies. This combination of frequenciesproduces the distinctive quality, or timbre, of a sound, which enables us to distinguisheasily between the same note played on a saxophone and on a piano. Everyhuman voice has its own distinctive timbre, which is why you can immediately identifya friend’s voice on the telephone from just a few words, even if you haven’ttalked to each other for years.How We HearThe Path of SoundThe ear is made up of the outer ear, the middle ear, and the inner ear. Sound wavesare collected in the outer ear, amplified in the middle ear, and transduced, or transformedinto neural messages, in the inner ear (see Figure 3.8).The outer ear includes the pinna, the ear canal, and the eardrum. The pinna isthat oddly shaped flap of skin and cartilage that’s attached to each side of your head.The pinna helps us pinpoint the location of a sound. But the pinna’s primary role isto catch sound waves and funnel them into the ear canal. The sound wave travelsdown the ear canal, then bounces into the eardrum, a tightly stretched membrane.When the sound wave hits the eardrum, the eardrum vibrates, matching the vibrationsof the sound wave in intensity and frequency.The eardrum separates the outer ear from the middle ear. The eardrum’s vibrationis transferred to three tiny bones in the middle ear—the hammer, the anvil,and the stirrup. Each bone sets the next bone in motion. The joint action of thesethree bones almost doubles the amplification of the sound. The innermost bone,