BBN ANG 141 Foundations of phonology Phonetics 3: Acoustic phonetics 1 Zoltán Kiss Dept. of English Linguistics, ELTE z. kiss (elte/delg) intro phono 3/acoustics 1 / 49
Introduction z. kiss (elte/delg) intro phono 3/acoustics 2 / 49
Introduction z. kiss (elte/delg) intro phono 3/acoustics 3 / 49
Introduction z. kiss (elte/delg) intro phono 3/acoustics 4 / 49
Introduction contrast beer bear z. kiss (elte/delg) intro phono 3/acoustics 5 / 49
Introduction contrast: how?? what makes the contrast possible? z. kiss (elte/delg) intro phono 3/acoustics 6 / 49
Introduction some basic terms z. kiss (elte/delg) intro phono 3/acoustics 7 / 49
Introduction acoustic cues z. kiss (elte/delg) intro phono 3/acoustics 8 / 49
sound waves acoustics definition and etymology acoustics is a branch of physics and is the study of sound (which is characterized as mechanical waves in gases, liquids, and solids) acoustic is derived from the Greek wordćkoustóc able to be heard it is concerned with the production, control, transmission, reception, and e=ects of sound it aims at describing and quantifying the properties of sounds with the help of various wave-related models acoustic phonetics deals with the acoustic properties and quantification of speech sounds z. kiss (elte/delg) intro phono 3/acoustics 9 / 49
sound waves what is sound? whenever there is a sound, there is: sound transmission sound source transmission through a medium (e.g., air, water) potential receiver/interpreter the definition of sound Sound is a potentially audible disturbance of a medium produced by a vibrating source. z. kiss (elte/delg) intro phono 3/acoustics 10 / 49
sound waves how to measure sounds? two problems: sound is invisible most sounds are fairly complex the task: make sound visible for analysis deal with the simplest sounds first z. kiss (elte/delg) intro phono 3/acoustics 11 / 49
sound waves the simplest sounds: pure tones the tuning fork emits pure tone z. kiss (elte/delg) intro phono 3/acoustics 12 / 49
sound waves the sound of the tuning fork z. kiss (elte/delg) intro phono 3/acoustics 13 / 49
sound waves simple periodic motion (SPM) the SPM of the tuning fork the tines of the tuning fork vibrate in simple periodic motion the tines move back and forth one fixed number of times per second (no matter how hard the fork is struck) periodic motion: the pattern repeats itself until it damps out z. kiss (elte/delg) intro phono 3/acoustics 14 / 49
sound waves simple periodic motion (SPM) the SPM of the tuning fork a complete movement: starting/rest position > maximum displacement > back over starting position > maximum displacement > back to starting position = a cycle (c) frequency (F): the number of completed cycles per second (s) (Hertz (Hz) or cps) the tines complete 440 cycles per second, frequency of the tuning fork = 440 Hz z. kiss (elte/delg) intro phono 3/acoustics 15 / 49
sound waves more simple periodic motion (SPM): the swing & the pendulum of the grandfather clock z. kiss (elte/delg) intro phono 3/acoustics 16 / 49
sound waves graphing SPM Let s try to record SPM in a graph! (demo) z. kiss (elte/delg) intro phono 3/acoustics 17 / 49
sound waves graphing SPM: sound wave/waveform z. kiss (elte/delg) intro phono 3/acoustics 18 / 49
sound waves graphing SPM: sinus waveform z. kiss (elte/delg) intro phono 3/acoustics 19 / 49
sound waves graphing SPM: sinus waveform z. kiss (elte/delg) intro phono 3/acoustics 20 / 49
sound waves 2 definitions waveform A graphical display of how amplitude varies over time. simple harmonic motion (SHM) A motion whose waveform is a sinus wave. the SPM of the tuning fork is a simple harmonic motion z. kiss (elte/delg) intro phono 3/acoustics 21 / 49
sound waves waveform properties 2 independent properties: 1. TIME, expressed as period (T) = time for a cycle to complete (expressed in seconds) in the graph T = 0.01 s OR frequency (Hz) = number of cycles in a second in the graph frequency =??? Hz 2. (PEAK) AMPLITUDE: the distance from the zero crossing z. kiss (elte/delg) intro phono 3/acoustics 22 / 49
sound waves the sound of the tuning fork z. kiss (elte/delg) intro phono 3/acoustics 23 / 49
sound waves the propagation of sound: pressure wave movement z. kiss (elte/delg) intro phono 3/acoustics 24 / 49
sound waves sound propagation (of the pure tone): summary SHM of sound source SHM of air particle set in motion by source air particle moves in sympathy with the SHM of source individual particle has limited motion areas of air compression and rarefaction /re@ri"fæksn/ are created compression and rarefaction areas move in time away from source, transmitting the SHM of source (pressure wave movement) listener senses same SHM as that of the source: sound has been propagated z. kiss (elte/delg) intro phono 3/acoustics 25 / 49
sound waves representations of sound propagation: waveform z. kiss (elte/delg) intro phono 3/acoustics 26 / 49
sound waves graphing SHM of air particles: waveform z. kiss (elte/delg) intro phono 3/acoustics 27 / 49
sound waves pressure-based graph variations in air pressure with respect to an equilibrium /i:kwi"libri@m/ z. kiss (elte/delg) intro phono 3/acoustics 28 / 49
sound waves pressure-based grap: sinuosoid waveform variations in air pressure with respect to an equilibrium /i:kwi"libri@m/ z. kiss (elte/delg) intro phono 3/acoustics 29 / 49
sound waves the sound of the tuning fork z. kiss (elte/delg) intro phono 3/acoustics 30 / 49
frequency change in frequency subjective sensation of pitch z. kiss (elte/delg) intro phono 3/acoustics 31 / 49
frequency some important facts about frequency when a sound is twice the frequency of another sound, it is an octave higher frequency range of human hearing: 20 Hz 20,000 Hz speech sound analysis usually involves the range between 100 Hz 10,000 Hz z. kiss (elte/delg) intro phono 3/acoustics 32 / 49
frequency change in amplitude subjective sensation of loudness/intensity z. kiss (elte/delg) intro phono 3/acoustics 33 / 49
amplitude the decibel: a measure of relative intensity why the decibel scale? air pressure amplitude is measured in pascals (Pa) the pascal scale is a linear scale: each increment is equal to the next the sensation of sound loudness/intensity is related to amplitude; however, it is not linear but logarithmic, that is, it is constructed with increments with increasingly larger numerical di=erences the decibel (db) scale (or sound pressure level (SPL) scale ) is a logarithmic scale of the amplitude of air pressure variations the db scale has intervals that are roughly equal to perceived loudness z. kiss (elte/delg) intro phono 3/acoustics 34 / 49
amplitude 0 db = 20 µpa (the threshold of hearing; the buzz of a mosquito around 3 meters away) z. kiss (elte/delg) intro phono 3/acoustics 35 / 49
amplitude 80 db ( 100000 µpa) (average street tra;c) z. kiss (elte/delg) intro phono 3/acoustics 36 / 49
amplitude 140 db (= 100,000,000µPa) (threshold of pain; jet engine at 25m distance) z. kiss (elte/delg) intro phono 3/acoustics 37 / 49
synthesis? what about complex sounds?! (speech sounds are nothing like pure tones!) z. kiss (elte/delg) intro phono 3/acoustics 38 / 49
synthesis how can we characterize complex waves? Jean Baptiste Joseph Fourier (1768 1830) key idea: if we can reduce a complex periodic waveform into a combination of sine waves then we can describe it using information about the frequency and amplitude of each component sine wave z. kiss (elte/delg) intro phono 3/acoustics 39 / 49
synthesis to build a complex wave is like a recipe, e.g., take 1 100 Hz/30 db sinus wave, then add 1 200 Hz/10 db sinus wave, and also add 1 300 Hz/20 db sinus wave This addition of two or more di=erent sine waves to create a complex periodic wave is called synthesis. z. kiss (elte/delg) intro phono 3/acoustics 40 / 49
synthesis waveform of a complex tone derives from 2 or more pure tones of di=erent frequency and/or amplitude z. kiss (elte/delg) intro phono 3/acoustics 41 / 49
synthesis three important consequences of synthesis the amplitudes of the complex wave depends on the addition of the amplitudes of the component waves the sine wave with the smallest frequency will define the main/basic repetition frequency of the complex wave: fundamental frequency f 0 the other sine wave frequencies present in the complex wave are called harmonics (H) (or: overtones); harmonics and f 0 harmonics are integer (whole number) multiples of the f 0 (this is because each sine wave component must complete a whole number of cycles within one period of the complex) z. kiss (elte/delg) intro phono 3/acoustics 42 / 49
harmonic analysis Our example complex wave has this harmonic series (also called Fourier series): Harmonic Frequency Amplitude H1 (= f 0 ) 100 (100 1) Hz 30 db H2 200 (100 2) Hz 10 db H3 300 (100 3) Hz 20 db harmonic analysis the reverse of synthesis, finding (characterizing) the component sine wave harmonics of the complex wave z. kiss (elte/delg) intro phono 3/acoustics 43 / 49
harmonic analysis Fourier s theorem (1822) All complex periodic waveforms can be analysed into a sum of sinusoidal component waveforms (harmonics). The mathematical algorithm of this process of harmonic analysis is called Fourier analysis or Fourier transformation. z. kiss (elte/delg) intro phono 3/acoustics 44 / 49
harmonic analysis? how can we graphically represent harmonic analysis? z. kiss (elte/delg) intro phono 3/acoustics 45 / 49
harmonic analysis spectrum graphs the (power/amplitude/line/sound) spectrum (plural: spectra): is a plot of the results of harmonic analysis frequency of harmonic: horizontal axis amplitude of harmonic: vertical axis time and phase: not shown (Fourier analysis is taken at a particular instant of time) z. kiss (elte/delg) intro phono 3/acoustics 46 / 49
harmonic analysis harmonic series of D harmonic freq. ampl. first (=f 0) 100 Hz (100 1) 30 db second 200 Hz (100 2) 10 db third 300 Hz (100 3) 20 db z. kiss (elte/delg) intro phono 3/acoustics 47 / 49
harmonic analysis loudness, pitch, quality: a summary all these components are independent of each other: sound loudness depends on amplitude sound pitch depends on f 0 sound quality/timbre depends on the spectrum (harmonic series) z. kiss (elte/delg) intro phono 3/acoustics 48 / 49
harmonic analysis contrast: depends on the spectrum beer bear z. kiss (elte/delg) intro phono 3/acoustics 49 / 49