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Acoustics Gk.akoustos “heard, audible" akouein “to hear”

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PIE *(s)keu- “notice, observe” skeu- keu- Gk akouein "to hear” akoustos "heard, audible" WG *skauwojanan OE sceawian “watch” Lat cavere “watch out” cautio “caution” Germanic *hausjan heyra OE hieran hear showskoða

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3 domains of phonetics articulatory phonetics acoustic phonetics auditory phonetics

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3 domains of phonetics articulation acoustics audition ))))))))))))))))))) ))))))))))))))))

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Acoustics and sentence stress We have seen that sentence stress consists of the prosodic features: pitch, length and loudness (Cruttenden 1986:2) to which we added vowel quality in Phonetics 1. In this slide show we'll consider only pitch and loudness

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Pitch and Loudness Pitch is determined by frequency - the speed of vibration of the vocal chords Loudness is determined by amplitude - the extent or breadth of vibration of the vocal chords

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“ah ah ah ah”

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“ah ah ah ah” Hz = Herz = cps = cycles per second

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Sentence stresses Sentence stresses are characterised by increased loudness changes of pitch

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Frequency The pitch of a speech sound is determined by the frequency of vocal-chord vibration. Frequency is usually measured in cycles per second (c.p.s) which are also called Hertz (Hz). Womens' voices can go up to 400 Hz; children's voices even higher. Average male voices range between 80 and 200 Hz

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Waves In most languages, the term 'wave' originally refers to the surface movements of water (bølge, Welle, onde, volná, tonn, aalto, to give some European examples).

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Waves Waves on water are a true example of natural waveforms, but it was not until the advent of electronic technology that we discovered that a large number of waveforms occur in the physical world.

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Waves Many are on too small a scale to be experienced as waves (sound- and light-waves) while others are too large (earthquakes, weather & climactic patterns, tidal movements, seasonal patterns, planetary movements). It is in fact possible to analyse a variety of natural and human processes as wave patterns: heartbeats, brain activity, population studies, the market, influenza epidemics, traffic flows (whether or not this always produces a useful analysis is another question.)

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Transverse and longitudinal waves þverbylgjur og lengdarbylgjur transverse: displacement across the direction of propogation longitudinal: displacement along the direction of propogation

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Transverse waves to-and-fro movement (or oscillation) across the direction of propogation, either from side to side or up and down Sea waves are transverse waves: the surface of the sea moves up and down as the waves travel over it

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Transverse waves If we use the data from this device to plot a graph showing the height of the sea above this stationary point on the sea-bed, we will get a picture in time which looks exactly the same as the spacial movement of the waves.

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Longitudinal waves to-and-fro movement in the same direction as the direction of the wave. compression & rarifaction (þétting og þan) travel along the line of the wave-motion see the animation at ttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/eds.gifttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/eds.gif in

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Longitudinal waves ttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/eds.gifttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/eds.gif %

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Longitudinal waves A graph of pressure changes at any one place plotted on a time axis looks like a transverse wave pattern

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Longitudinal waves Sound waves in air are longitudinal waves, but they can be represented in this way as transverse waves x= eardrum / microphone

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Sine waves Latin sinus 'a curve' regular frequencies simple harmonic motion –pendulum –tuning fork.

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Sine waves Pure tones. When a soundwave is a pure sine- wave, we hear it as a pure tone. Soundwave of pure middle A, which is 440 Hz.

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Sine waves Some fairly pure examples: my tuning-fork (pitchfork?) Praat – PK 27 Sep 2009

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Sine waves Some fairly pure examples: whistling Praat – PK 27 Sep 2009

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Complex waves Adding 2 sine equal waves:

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Complex waves Adding: various frequencies

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Recorded in SoundEdit between

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Recorded in Praat 27 Sep 2009

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Reasons for difference: phasing (I think) Impossible to read the formants from the waveform. This problem is is overcome by Fourier analysis -- which finds the same formants although the the phasing is different. This comes a few slides down

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periodic and aperiodic: complex soundwaves periodicity not as regular as pure tones, since each 'period' is slightly different from the previous one Human speech-sounds are not pure, but dynamic sounds: their frequency is continually changing, and so is the shape of the sound-wave.

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“shoe”

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“fish”

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Fourier analysis In December 1807, the French physicist and mathematician Jean Baptiste Joseph Fourier ( ) read a memoir on "the propagation of heat in solids" at the French Institute. David A Keston /~davidk/fourier.htm

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Fourier analysis The mathematics behind this method of analysis are what are known today as the Fourier Series, a branch of calculus which can be used to calculate the pure sine wave components of a complex wave. The idea is that complex periodic waves can be broken down into a (sometimes very large) number of pure waves which when added together produce the complex wave.

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Fourier analysis In linguistic acoustics, we find that different vowels have their own typical arrangements of components, which we call formants.

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Fourier analysis The basic or fundamental frequency - usually referred to as F0, is the frequency of the greatest period, the complete repetitive cycle. This is the frequency we hear as pitch when we are working with intonation.

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How Praat computes pitch (make a video)

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Complex waves Adding 2 sine equal waves:

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Adding waves with close frequencies

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Adding 2 waves, varying the phasing of the second wave

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Varying the phasing of identical waves Adding two waves phased alike

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Varying the phasing of identical waves Phasing of second wave 140°

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Varying the phasing of identical waves Phasing of second wave 170°

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Varying the phasing of identical waves phasing of 2nd wave 180°

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3 domains of phonetics articulation acoustics audition ))))))))))))))))))) ))))))))))))))))

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