Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download image by Hans-Christoph Steiner based on Grey, JM 1979, JASA
Document related concepts
Transcript
On Timbre Phy103 Physics of Music Four complex tones in which all partials have been removed by filtering (Butler Example 2.5) One is a French horn, one is a violin, one is a pure sine, one is a piano (but out of order) It’s hard – but not impossible to identify the instruments. Clues remain (attack, vibrato, decay) and these contribute to the “timbre”. Timbre is not just due to the spectral mix. Attributes from Erickson’s Music Structure Subjective Objective Tonal character, usually pitched Periodic sound or sound composed of only a few frequencies Noisy, with or without some Random pulses or broad tonal character, including band spectrum rustle noise Vibrato Frequency modulation Tremolo Amplitude modulation More Attributes Coloration Spectral envelope Coloration glide or formant glide Change of spectral envelope Attack Prefix Final sound Suffix Beginning/ending Rise/decay time Schouten’s “Acoustic parameters” 1. 2. 3. 4. The range between tonal and noiselike character. The spectral envelope. The time envelope in terms of rise, duration, and decay. The changes both of spectral envelope (formant-glide) and fundamental frequency (micro-intonation). 5. The prefix, an onset of a sound quite dissimilar to the ensuing lasting vibration. This represents way too many free parameters for an engineer to cover the complexity of sounds. Timbre space • • Grey’s Timbre cube Is it possible to classify timbres, for example recognition of instrument from audio? image by Hans-Christoph Steiner based on Grey, JM 1979, JASA, 61, 1270 Timbre space based on nearness ratings by people Psychology experiment From McAdams, S. et al. Psychological Research, 58, 177-192 (1995) Broad band vs Tonal “Beat That” by Beat Kaufmann Hz The Syrinx Filtered Broad Band • ASA demo 5 • A Low pass filter cuts off all high frequencies Blending of harmonics into one tone or timbre ASA Demo 1 Cancelled Harmonics 20 harmonics of 200Hz are played together. When the relative amplitudes of all 20 harmonics remain steady they blend and we hear them all as one tone When one harmonic is cancelled or given a vibrato then it stands out and we hear it separately How many harmonics are needed for a tone to have its recognizable character? • ASA Demo 28 Adding in partials of a carillon bell Hum note 251 Hz Prime or fundamental 501Hz Minor Third and Fifth 603,750Hz Duodecime or Twelfth 1506Hz Upper Octave 2083Hz Next two partials 2421,2721Hz Remainder of partials Adding in partials for a guitar ASA Demo28 In order • • • • • • • • fundamental 2rd harmonic 3rd harmonic 4th harmonic 5th and 6th harmonic 7th and 8th harmonic 9th, 10th and 11th harmonic Remainder What are the characteristics of sounds used for music? Properties of musical sounds • Composed of tones, not alot of broad band noise • Overtones are nearly harmonic • Lots of exceptions to the above rules Timber and Transposition • High and low tones from a musical instrument do not have the same relative spectrum. • Low notes on the piano have week fundamentals whereas high notes have strong ones • ASA Demo30 shifting the spectrum of a bassoon down The effect of Tone Envelope on Timbre ASA demo29 Piano envelope is normally decaying but here it is reversed Tones and Tuning Stretched The scale can be stretched The partials can be stretched Here are examples of all 4 combinations -- pure harmonics and normal scale -- scale stretched -- partials stretched -- stretched harmonics and scale 1 octave=2.1 Changes in Timbre The singer’s formant • Cook demo 42 Singing with and without the singer’s formant spectrum with singer’s format spectrum without Changes in timbre with vocal effort Cook demo #78 a) b) c) d) Successive vocal tones, amplitude only turned down Same as a) but high end of spectrum is also turned down, as would happen for decreasing effort Same as b) but with additional reverb that is held constant so voice sounds like it is getting quieter in a fixed location Same as a) but with increasing reverb so the voice sounds as if it is getting further away Terms Introduced • Timbre space and popular choices for their dimensions
