PY2507.1 ~ {Communication by sound} 2.0
broad band sounds
refer to noises or signals that contain a wide range of frequencies, as opposed to narrowband sounds that are confined to a specific range [including speech]
freq spectrum of a sound
the distribution of the different freqs that make up that sound + shows how much energy is present at each freq within the sound [graph where x-axis = freq (in Hz), y-axis = amplitude or intensity of each freq
what is a potential way of distinguishing one spoken vowel from another
having hearing system that is capable of reprresenting these diff peaks in spectrum + how they move to diff positions when diff vowels are heard
logarithmic frequency scale
a sound that goes from 100 Hz - 200 Hz is seen as having a similar "pitch" change as one that goes from 1,000 Hz - 2,000 Hz, even though the freq diff is much larger in the second case [each successive interval represents a multiplication of the previous frequency rather than a simple addition]
why is logarithmic freq scale useful
allows you to represent a wide range of frequencies more compactly, which is especially useful when dealing with sounds that cover many orders of magnitude (like 20 Hz to 20,000 Hz in human hearing)
which part of ear responds to what
basal end - high freq
apical end - low freq
excitation level
measure of neural activity [firing of neurons]
excitation pattern
plot of excitation level against distancealong the basilar membrane - the auditory spectrum of sound [how its freq content is represented in the ear's neural response]
how does cochlea act
as freq analyser by converting sound waves [vibrations in ear] into electrical signals that the brain can interpret
what is language
a system based on symbols based on rules for organizing those symbols + system of communication that allows individuals to express thoughts, ideas, emotions, and information to others
symbol
represents or stands for something else, in language they are used to convey meaning ideas or concepts that are understood through shared agreements or associations
how many words do we typically use
95% of time we use a lexicon [word store] of 5 - 10k words [but we know hundreds of thousands]
phoneme
basic units of language - smallest unit of language that can differentiate one word from another
how many phonemes in english
40 which form 2 classes [vowels + consonants] which is more open vs closed configurations
phones
each phoneme may be represented in speech by one or more speech sounds = phone
free variation
an instant where a particular phoneme can be represented by more than one speech sounds and its the speakers disgression as to which one they use
allophone
diff realizations or pronunciations of the same phoneme that occur in different contexts but do not change the meaning of the word + often a result of the influence of surrounding sounds, stress, or the position of the sound within a word
pin vs spin
p sound in pin is aspirated [pronounced with a small burst of air] whereas p in spin is unaspirated [both are allophones of the same phoneme p but occur in diff positions in the word]
allophone occuring in free variation
can be used interchangeably in certain contexts without changing meaning of the word [butter can be pronounced as budder - allophones of the same phoneme]
bio function of vocal organs
is not speaking its actually chewing + breathing + swallowing these organs have been modified over the course of human evolution to produce speech sounds
breathing
is controlled by the muscles of the rib cage + the diaphragm + abdominal muscles - so all around lungs [we normally breathe once per 5 seconds with equal periods of inhaling and exhaling]
breathing cycle in relation to speech
when we speak we change the rate + pattern of our breathing accordingly, given that we only talk when exhaling we can adjust the bc to devote as little as 15% of the time to inhaling
flow of air
comes from the lungs then through trachea [wind pipe] then through the larynx [voice box] then goes up into upper sections [vocal tract = everything above larynx]
2 outlets of air
[main one] through the mouth cavity and out through mouth + soft palet [velum] can either stay low which allows airflow through nasal cavity or can be raised to shut it off
most cases when talk we shut off the nasal cavity [unless we say nasal words]
larynx
constructed of a stack of cartilage rings + acts as a valve between the lungs and mouth - it automatically moves up under the epiglottis + closes during swallowing to prevent food entering the trachea
thyroid cartilage
enlarges in adult men forming adams apple + largest one at the front
valave action of larynx
depends on the arytenoid cartilages [back + moveable] and the vocal cords which are also critical for speech production
vocal cords
2 folds of ligament inside the larynx that extend from thyroid cartilage[front] to arytenoid cartilages [back]
glottis
space between the vocal cords [v-shaped when open] - when shut airflow is shut off - swallowing + talking [but not shut tightly]
phonation
aka voicing - when we speak the vocal cords close + pressure builds up until a brief pulse of air is released [process is repeated many times a second] - voive pitch corresponds to rate of vibration
glottal source
sound produced by phonation + buzz like sound has a very distinct spectrum, freq components ar eequally spaced the higher ones are said to be harmonic as the lowest one - depict the pitch of the voice and higher ones are exact multiples of it + so 2nd one twice freq of the first as so on
voice pitch
corresponds to rate of vibration + depends on length & tension of vc & pressure from lungs - all these factors can be controlled within limits by the speaker + depends on 3 factors how long the vc are how much tension is on them + how much pressure is coming from the lungs
normal pitch range for speech
from about 60Hz [deep male voice] to 350Hz [infants voice] + the more pulses per second they are the higher the pitch of the voice
vocal tract
extends from the glottis to the lips [basically everything above the larynx] + about 17.5 cm long [for men] like 14cm for women
mouth cavity
most important part of the vocal tract - its size + shape can be varied extensively by adjusting positions of the tongue lips + jaw
velum
aka soft palate - usually raised when speaking to close off the nasal cavity [except when articulating nasal consonants]
artculation
the process of producing speech sounds
neutral [Schwa] vowel
'uh' - is produced when the tongue is in the centre of the mouth [widt area of vocal tract is approx constant for thos vowel
main factor influencing shape of vt
position of the tongue - this is defined as the location in the mouth of the highest part of the main body of the tongue
lip position
affects both shape + length of the vocal tract [lip rounding extends the vt as well as changing its shape] lip reading can also provide visual info about articulation
lip positions for english words
front - spread [ee]
low back - unrounded [a]
high back - rounded [u] - applies to sone consonants like [sh/w]
vowel chart
diagram that visually represents the sounds of vowels in a language typically showing how they are produced in terms of their articulation in the mouth
how are vowels classified
2 main ways - height [vertical position of the tongue] + backness [horizontal position] + rounding [whether the lips are rounded or not]