Chapter 14: Speech Perception Flashcards
What are some common problems with automatic speech recognition?
It is no where close to human speech recognition abilities. It gets easily confused by unfamiliar phrases, background noise, and varying pronunciations.
What is an acoustic signal?
The acoustic signal is caused by air pushed up from the lungs into the vocal tract and through the vocal cords. It is altered by articulators including: the tongue, lips, teeth, jaw, and soft palate.
What are Formants?
Formants are frequencies at which peaks of pressure arise from different speech sounds. The first format has the lowest frequency, second has the next highest etc.
Formant transitions are rapid shifts in frequency preceding or following formants. These are often associated with constant sounds that are produced by restricting and narrowing the vocal tract.
What is a phoneme?
Phonemes are the smallest unit of speech that can change the meaning of a word. In english there are 47 phonemes but that number varies across languages (e.g. Hawaiian only has 11 while some African dialects have 60).
What is the variability problem in speech perception?
The variability problem is that there is no simple relationship between a particular phoneme and an acoustic signal, the acoustic signal for a phoneme is very variable. This challenges the idea that speech is just a matter of perceiving a series of discrete sounds strung together.
This variability comes from multiple sources
- Coarticulation is the overlap between articulation of neighbouring phonemes where an acoustic signal for one phoneme is dependent on the phonemes said before and after it.
- Other sources: differences in pitch, speed, accent, pronunciation.
What is the motor theory of speech perception?
The motor theory of speech perception proposes that we understand speech because we know how to produce the sound itself. Essentially, hearing a sound triggers the motor processes associated with producing that sound.
This theory claims that speech perception is special from other forms of auditory perception and uses phonetic boundaries to differentiate sounds
What are phonetic boundaries and how do they relate to perceptual constancy?
Phonetic boundaries are the voice onset time where perception changes from one category (phoneme) to another. E.g. the Voice Onset time where perception changes from perceiving Ba to Pa.
Perceptual constancy is the idea that stimuli on the same side of the phonetic boundary are perceived as being the same.
What are 5 different sources of information we use for speech perception?
- Motor Processes: the same brain region can respond to both the perception and production of speech.
- Face and lip movements: speech perception is multi-modal in that we use visual, auditory, and even tactile sources of info
- Knowledge of language: we use what we know about language to help us perceive speech.
- Meaning and context: we use the context of the speech and our knowledge of general meaning to perceive speech. For example, if someone were telling us about their garden and we were having trouble hearing them we could use meaning and context to know that they said they planted lots of “carrots” not lots of “hairnets”
- Transitional Probabilities: the chances that one sound will follow another. This changes depending on the language and is formed through statistical learning.
What is the McGurk effect?
The McGurk effect is when we hear a sound based on lip movement even when it doesn’t match the actual audio. E.g. hearing fa fa fa when the audio is actually saying ba ba ba.
What is phonemic restoration?
When we fill in missing and or disrupted phonemes based on what is expected to be there.
What is Speech Segmentation?
It is our ability to perceive breaks and gaps in speech due to our familiarity with language rules. (our ability to know where one word ended and another began) If we listen to an unfamiliar language, we are not able to do this.
How do we perceive speech in difficult audio circumstances?
We rely heavily on top-down processing. The longer we spend in the adverse conditions, the better we get at understanding speech.
What are the functions of Broca’s and Wernicke’s areas and what occurs if these areas are damaged?
Broca’s Area: responsible for prodcuing speech. When damage to this area occurs, Broca’s aphasia develops and the person has difficulty producing speech and particular trouble connecting words.
Wernicke’s Area: responsible for speech comprehension. When damage to this area occurs, Wernicke’s aphasia develops and the person has difficulty comprehending speech or producing meaningful speech.
What is the voice area and where is it?
The voice area is found in the temporal sulcus. cells in this area are stimulated by human voices.
What is the dual stream model of speech perception?
This model suggests that the ventral stream supports speech comprehension and the dorsal stream supports the linking of acoustic signals to the movements used to produce speech.
It suggests that some cells are specialized for single phonemes and some for phonetic features like the manner and place of articulation.
