CH 03: Speech Perception

What is meant by lower-order processing → higher-order processing in sound perception?

Lower-order processing involves detecting basic physical properties of sound (frequency, amplitude), while higher-order processing involves interpreting these signals as meaningful sounds (speech, language) in the brain.

What is the difference between frequency and pitch?

Frequency is an objective physical measure of sound waves (Hz), while pitch is the subjective perceptual experience created by the brain from frequency information.

How does amplitude relate to loudness?

Amplitude is the physical intensity of sound waves; greater amplitude leads to the perception that a sound is louder.

What is a complex sound?

A sound composed of multiple pure tone components called harmonics.

What is the fundamental frequency, and what role does it play?

It is the lowest frequency in a complex sound and determines the perceived pitch of the sound.

What are harmonics and how are they related to the fundamental frequency?

Harmonics are higher-frequency components that are integer multiples of the fundamental frequency (e.g., 200, 400, 600 Hz).

Why do we perceive a complex sound as a single sound rather than multiple frequencies?

The auditory system integrates the harmonics into one perceptual experience.

What is timbre?

The quality or identity of a sound that allows us to distinguish sounds with the same pitch and loudness.

Why do a flute and a violin sound different when playing the same note?

They differ in the relative amplitudes of their harmonics, producing different timbres.

What is the function of the pinna?

It collects incoming sound waves.

What happens at the tympanic membrane?

It vibrates in response to sound waves.

Name the three ossicles and their role.

Hammer, anvil, and stirrup; they transmit and amplify vibrations from the tympanic membrane to the cochlea.

Why must the ossicles be made of bone?

To transfer sound efficiently from air into fluid within the cochlea.

How is the cochlea physically tuned for frequency?

Different locations respond best to different frequencies.

Which part of the cochlea responds to high-frequency sounds?

The base (up to ~20,000 Hz).

Which part responds to low-frequency sounds?

The apex.

What is the role of the basilar membrane?

It moves in response to sound frequency and activates sound receptors.

What is the resonant frequency range of human speech?

Approximately 100–300 Hz.

What is a tonotopic map?

A spatial representation of sound frequencies from the cochlea recreated in the auditory cortex.

Why is tonotopic mapping important?

It allows conscious identification and accurate perception of sounds.

How do auditory signals from each ear project to the brain?

Signals from each ear travel to both left and right auditory cortices.

What is the right ear advantage for speech?

Speech sounds entering the right ear project more directly to the left hemisphere, which specializes in language.

What are the stages of the speech stream?

Sound → Sensory processing → Language processing.

What is a phoneme?

The smallest unit of sound that can change meaning in a language.

How many phonemes are there in English?

Approximately 40.

Why can limited phonemes create unlimited meanings?

Because phonemes can be combined in countless ways.

What is coarticulation?

The phenomenon where phonemes are pronounced differently depending on surrounding phonemes.

Why does coarticulation occur?

Speech sounds are produced in relation to one another, not in isolation.

What is categorical perception in speech?

The tendency to perceive speech sounds as belonging to discrete categories rather than as continuous variations.

Why is there “no middle ground” between phonemes like /ba/ and /pa/?

Once acoustic input crosses a boundary, it is categorized as a different phoneme.

What is the Ganong effect?

The influence of lexical knowledge on phoneme perception.

Why would people hear “task” instead of “dask”?

Because “task” is a real word and “dask” is not, so perception is biased toward meaningful words.

What is phonemic restoration?

The perceptual filling-in of missing speech sounds using context.

Why do people report hearing a sound that was replaced by a cough?

The brain restores the missing phoneme based on sentence logic.

Why are grammatical sentences easier to shadow than anomalous ones?

Because meaningful syntax allows prediction of upcoming words.

Why are ungrammatical sentences nearly impossible to shadow?

They violate syntax and lack predictable structure.

How do researchers know fetuses recognize familiar speech?

Changes in heart rate when hearing familiar vs. unfamiliar nursery rhymes.

What is the high-amplitude sucking technique?

Infants suck harder when hearing familiar sounds.

What does infant-directed speech accomplish?

It maintains infants’ attention and enhances learning.

What is prosodic bootstrapping?

Using rhythm and stress patterns to infer word boundaries.

What is the trochaic structure of English?

Stress is placed on the first syllable of most words.

How do tone languages differ from stress-based languages?

Word meaning changes based on tone rather than stress.

What is statistical learning in infants?

Learning language patterns based on transitional probabilities between sounds.

How do researchers test statistical learning in babies?

Using visual fixation tasks to measure attention to novel sound sequences.

What is perceptual narrowing?

By around 1 year of age, infants become specialized in perceiving sounds from their native language.

What does motor theory propose about speech perception?

We perceive speech by inferring the motor movements required to produce it.

What neural evidence supports motor theory?

Activation of motor areas during passive speech listening and effects of rTMS.

Why does infant phoneme discrimination challenge motor theory?

Infants can discriminate phonemes they cannot yet produce.

Why do nonhuman animal studies challenge motor theory?

Animals like chinchillas can discriminate speech sounds without speech motor systems.

How does the general auditory framework differ from motor theory?

It treats speech as one of many sounds learned through experience, not a special motor-based signal.