LIN228H1 Lecture Notes - Lecture 4: Fundamental Frequency, Formant, Spectrogram

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26 Mar 2017
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October 5th, 2016
LIN228 LECTU R E 4: ACOUS TI C PHONE TI CS
A little introduction…
oSpeech sounds can be described based on how they’re made (articulation)
oHow they’re transcribed (transcription; written)
oHow they can travel through the air i.e. transmitted and become heard (acoustic structure, today’s lecture)
This time between when the sound is emitted before it is heard defines the acoustic structure
Acoustics is concerned with sounds in general, whether it’s a bird chirping or a person speaking
Acoustic phonetics studies the acoustics of speech sounds specifically
Why do we care?  Important in the perception and interpretation of speech sounds
oIn the transcription of sounds, we’re also not always sure about how correct we are (especially with narrow
transcription)
oBy studying the acoustics of sounds, we determine information that can shed more light on the character of
sounds
oOther vowels are better described acoustically than when they are described articulatorily  a lot easier to
characterize vowels via acoustics
PROPAGATION OF SOUND
Our analogy:
oThe distance between two people is described as rarefaction
As the people move forward to get their ticket, the distance between them increases; rarefaction
describes this distance
Rarefaction  travels along the line as each person goes up to get the ticket
oCompression describes the lack of distance between two individuals
Similar to rarefaction, it will travel along the line
oWe then return to the condition we were at initially (at time point 1)
We can represent this situation graphically  at time point 2, the crowdedness between 1 and 2 drops due to the two
people being further apart, and at time point 11, the crowdedness spikes due to the two people coming closer
A sound wave is a travelling pressure fluctuation
oPropagates through the medium (air); we can hear the sound because the rarefaction and compression patterns
hit our eardrums
oThe patterns are typically cyclic
A waveform is one method of displaying sound information  two dimensions: amplitude and time
SIMPLE PERIODIC WAVES
AKA Sine waves  symmetrical “S” shape and has two dimensions: time and amplitude
Amplitude: the degree of variation from 0 (neutral); measured in hecto-Pascals or millibars
oThe greater the amplitude = the louder the sound
o0 acts as the threshold of hearing
Intensity: also corresponds with loudness
Frequency: the number of cycles per second; measured in hertz
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