Chapter Seven
The Auditory System: Music and Speech Perception
Chapter Outline
Two very common auditory tasks are the perception of music and the perception of
speech, and this chapter focuses on how the auditory system processes these sensory
signals. The chapter begins with music perception. You will learn about musical pitch,
musical scales, and timbre (or tonal quality). Aspects of music perception, such as
monophonic (single) and polyphonic (multiple) tones, will be discussed, as will tonal
sequences, which include melody, tempo, and rhythm. Gestalt theory, as an account for
the global perception of melody, will also be explained. You will then learn about the
brain areas implicated in the processing of music.
The focus of the chapter then shifts to speech perception. Humans have a
remarkable ability to perceive speech sounds given that the signal is simply a stream of
sound. To highlight this, listen to a language you do not understand. You will probably
perceive it as a continuous string of noise, and yet with our native language we can
effortlessly pick out individual words from the speech signal. To aid in your
understanding of this process, the section begins with an overview of the anatomical
structures responsible for producing speech. The basic sounds of speech, called
phonemes, which can be combined to produce words, are then discussed. Sound
spectrograms are used to examine the characteristics of a stream of speech as sound
frequency and the associated intensity unfold over time.
The comprehension of speech is then addressed. This begins with an overview of
features that define a language and an outline of the field of psycholinguistics. Next, the
perception of vowel and consonant speech sounds is considered. We classify speech
sounds in a broad manner and this is known as categorical perception. Three major
issues for speech perception are then discussed. These issues are: the segmentation
problem, which relates to how we identify individual words in a speech stream; the
variation problem, which suggests that even when there is variability in the speech
signal, such as with accents and general differences between people in pronunciation,
we are still able to discern meaning from the signal; and the coarticulation problem,
which occurs when a particular speech segment (e.g., a phoneme or word) influences
the sound of neighbouring speech segments in the speech stream, yet we still perceive
the intended segment correctly. We also have a great ability to fill in missing phonemic
segments, for example, if a cough obscures part of a word you will likely still perceive
the intended word correctly, and this is an example of the phonemic restoration effect.
The chapter concludes with an overview of language processing in the brain and a
discussion of Wernike’s aphasia and Broca’s aphasia, two conditions that result from
damage to separate areas in the left hemisphere that affect language. 2
Learning Objectives
This chapter will help you
contrast how music differs from isolated tones in how the fundamental frequency
and harmonics activate the basilar membrane of the cochlea. They will also
become familiar with timbre as the measure of quality of musical sound. If you
are familiar with musical theory, you will be able to relate the concepts of the
musical octave and representing pitch to your own experiences.
think critically about suggestions by evolutionary psychologists that music
evolved because of its adaptive purposes
describe tonal superpositions and explain the difference between a consonant or
dissonant superposition. Likewise, you should understand what a tonal sequence
is and, from a musician’s perspective, how these sequences relate to melody,
tempo, and rhythm. You should also be able to explain the perception of tonal
sequences using the principles of Gestalt theory.
identify the cortical areas involved in the perception of pitch and describe how
pitch perception is affected when these areas are damaged by injury or stroke.
understand that language in humans is a universal ability and, although there is
great variation across cultures, all language share common characteristics.
identify the structures involved in the production of speech as well as their
functions. You should also be familiar with the basic speech sounds (phonemes)
and how they are classified according to their place of articulation and manner of
constriction.
describe the acoustic properties of speech including the waveform, frequency
characteristic and the spectrograph. When looking at a spectrograph, you should
be able to identify the formants and describe how these acoustic cues allow us to
isolate and recognize speech sounds in speech perception. 3
discuss the categorical nature of speech that varies according to changes in
voice onset time. You should also understand the concept of co-articulation and
how this aids in the perception of consonant sounds while still presenting
challenges.
describe the process and results of the phonemic restoration effect and the
McGurk Effect as well as what these phenomena tell us about speech
perception.
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