Physics of Sound and Music I week 9 pitch and timbre Pitch ( perde, aralık) timbre (tını, ses rengi) if we start with a pure tone, there is a correspondence between the frequency of the sound and our perception of the frequency (pitch). the pitch depends on the loudness level on the spectrum (timbre) of the frequencies in the sound on the duration on the attack ( the start of the sound) pitch attributes of the auditory sensation which in turn maps onto a musical scale subjection two people listening to the same sound may assign a different position on the pitch or musical scale Physics of Sound and Music I week 9 pitch and timbre Pitch ( perde, aralık) timbre (tını, ses rengi) e.g. the sound pitch in the right ear can be different from the sensation produced in the left ear (binaural diplacusis - çift işitme) basic unit of pitch - OCTAVE the notes just an octave apart are on the frequency ration of 2:1 discussed by Pythagorus in 5th century BC. Standard Frequency Ratios Ratio Name 1:1 Unison 1:2 Octave 1:3 Twelfth 2:3 Fifth 3:4 Fourth 4:5 Major Third 3:5 Major Sixth Physics of Sound and Music I week 9 pitch and timbre the correspondence of the physical frequency and the perceived pitch. the frequency is given in units of Hz, while the perceived pitch is in units of mels at f = 1000Hz, the critical bandwidth along the basilar membrave is 160Hz this corresponds to 100mels Physics of Sound and Music I week 9 pitch and timbre experiment on OCTAVE let f = 4000Hz listen and memorize this patch reduce the pitch; ask the person to step when the pitch is 1/2 of 4000Hz or 2000Hz typical result: person chooses a pitch about.... PD exercise Physics of Sound and Music I week 9 pitch and timbre experiment on OCTAVE let f = 4000Hz listen and memorize this patch reduce the pitch; ask the person to step when the pitch is 1/2 of 4000Hz or 2000Hz typical result: person chooses a pitch about 1000Hz? Physics of Sound and Music I week 9 pitch and timbre Pitch Discrimination ( perde ayırtetme) ability to distinguish between two notes defined as jnd = just noticeable difference jnd is frequency dependent sound level dependent duration of tone dependent suddenness of frequency change dependent The difference limen is that difference or change in the stimulus that is at the threshold of detectability we plot the jnd and critical bandwidth vs frequency CB is related to the physical stimulation along the basilar membrane in the inner ear between frequencies f= 1000HZ and f = 4000Hz the jnd is jnd ≈ 0.5% f = 0.005 f Physics of Sound and Music I week 9 pitch and timbre Pitch Discrimination ( perde ayırtetme) ex. f = 1KHz jnd = ? jnd = 0.005xf = 0.005 x 1000 = 5Hz for hearing we are sensitive to 10 OCTAVES, which is equivalent to 5000 jnd Physics of Sound and Music I week 9 pitch and timbre Pitch Perception and Sound level how we perceive different frequency pure tones as we change the sound level - lower frequencies (f =200) the perception of the pitch decreases as we increase the sound level, The sound level form 40dB to 90dB - higher frequencies ( f 4000Hz - 6000Hz) the perception of the pitch increases as we increase the sound level Physics of Sound and Music I week 9 pitch and timbre Pitch Perception and Sound level how we perceive different frequency pure tones as we change the sound level - middle frequencies (f ≈ 1000Hz) show little change in perception as we increase the sound level this is somehow small effect and most of the people can not really experience this phenomenon the change is 1% of the frequency for C4 = middle C = 262 Hz pitch change is ≈ 2.6 Hz which in many case it is the jnd unit cent previously we talked about an octave which is a frequency ratio of 2:1 if we break up the octave into 12 equal intervals = > the resulting frequency ratio for a single note (called semitone) is 1/12 of an octave which is about 1.059% between notes we further breakdown the semitone interval into 100 equal parts = cent Physics of Sound and Music I week 9 pitch and timbre Pitch and Duration how long does a tone need to be heard in order for a person to perceive it as an identifiable pitch? about 2 - 5 full cycles of the sound depends on the frequency and the wavelength if f = 50Hz period T = 1/ f = 1/ 50 = 0.02s = 20ms Time required ≈ 2 times the duration = 40ms experimentally minimum time required to create musically perceptible sound is 3ms if the time is less then 3 ms, the we hear series of clicks, the transition of the clicks to a tone depends on the sound level Physics of Sound and Music I week 9 pitch and timbre Pitch of Complex tones - Virtual Pitch if a particular instrument played a tone in which the following frequencies are present 600Hz, 800 Hz, 1000Hz, 1200Hz we would perceive the pitch= ? demo --” Missing Fundamental” we percieve the pitch of this complex tone to be f₁ = 200Hz, the lowest common factor of in the complex tone, of 600Hz, 800 Hz, 1000Hz, 1200Hz PD exercise Physics of Sound and Music I week 9 pitch and timbre Pitch of Complex tones - Virtual Pitch in this case we play f₃, f₄, f₅, f₆ we hear only the fundamental f₁ = 200Hz This has been found experimentally that it is the best to have forth and fifth harmonics present to hear the missing fundamental our brain supplies the missing fundamental. This is no or very little power in the fundamental but we repeat hearing the fundamental Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch Place vs Periodicity we have discussed the the place theory previously, Signals from the basilar membrane (place theory) travel to the brain and are interpreted as a specific pitch the ear performs both frequency and time analysis; the brain does extensive computations in order to determine the pitch vibrations of different frequencies excite different areas along the basilar membrane => the place theory cochlea converts vibrations in time to vibrations in space along basilar membrane Helmholtz regarded basilar membrane as a frequency analyzer, different parts are tuned to different frequencies e.g. high frequency excite oval window, low frequency at far end Békésy experimented with the same result as well Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch Place vs Periodicity problems with the theory - fine frequency determination to respond to changes in frequency = > damping (sönük) damping decreases selectivity - can not distinguish small changes in frequency complex tone sound heard or perceived as one pitch rather than many Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch Place vs Periodicity Periodicity theory ear perform time analyses time distributes on auditory nerve to brain decoded by central nerves system 1930 Schauten experiment missing fundamental experiment 600Hz, 800 Hz, 1000Hz, 1200Hz = f fundamental is 200Hz if we play complex tone frequencies together with 206Hz tone, 206 should beat with 200Hz, but it doesnt, because processing happens inside the brain, this is where the interpretation takes place Schauten pitch shift phenomena is due to the synchronous firing of auditory nerve Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch Place vs Periodicity Periodicity theory Repetition pitch changes with time delay T = time delay = L / v L= distance v = velocity perceived pitch = f = 1/ T = v / L 1-7ms to distinguish blind persons make use of this phenomenon to locate abstractions by interaction of direct + reflected sounds repetition pitch is due to interference between noise and its delayed repetition Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch The ability to recognize and define pitch of a tone without a reference compare with color perception ability to recognize green without a comparison spectrum %98 of people can do this task %2 color blind can not do this task 1 in 10000 people have absolute pitch absolute pitch vs relative pitch we can tell if one tone is higher or lower than another ex 1000Hz -- go up one octave --- 2000hz actually it can be 2046 or 2035 Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch absolute pitch theories Heredity theory people learn pitch names like color names in early life , but is born with the ability Learning theory anyone with practice (constant) can learn Unlearning theory ability is universal, but it is trained out of people - emphasis of relative pitch Imprinting theory rapid irreversible learning that takes place at a specific development state Physics of Sound and Music I week 9 pitch and timbre Theories of Pitch people with absolute pitch recognition often make 1 octave errors in identifying tones also it can vary with age person with perfect pitch age 52 --> C --> C# age 71 --> C --> D Physics of Sound and Music I week 9 pitch and timbre speech in tone language speech sound can take on several meanings depending on the tone typically have absolute pitch ( or close to it) Chinese ( Mandarin ) on Vietnamese language the sound of “ma” Pitch standarts note “A” = f = 374Hz - 567Hz pipe organs 1619 Praetorians = > 424 Hz defined as “A” Händel’s tuning fork = 422.5Hz 1859 = > French government = 435 Hz scientific pitch ( powers of 2) 126, 256, 512 - for C’s => A = 431Hz 1939 440Hz in International Conference in London pitch raising ex 442 to 444 some instrument designed to be played at certain pitch, and it sounds terrible if tuned differently clarinet greatenes Physics of Sound and Music I week 9 pitch and timbre pitch raising singers usually sing about a semitone above pitch where they were written old violins strengthened as to play at higher pitch tuning forks are used as standards short wave radio station in US - 440Hz tone broadcast string instruments pitch falls as temperature rises string expends = tension lowered wooden instruments velocity of sound increases for 0.6m/s for each Celsius Degrees, so the pitch of a wind instrument raises about 3 cents ( 3/100 semitones) per degree of temperature raise- Physics of Sound and Music I week 9 pitch and timbre timber or tone quality timber french word is used for tone quality or tone color definition Timber is that attribute of auditory sensation in terms of which a listener can judge two sounds similarly presented and having the same loudness and pitch as dissimilar.