한국과학영재학교 http://www.ksa.hs.kr

1. 1 2 3 4 5 6 7 8 새로운 음원 합성 방법에 대한 연구 A Study on New Sound Synthesis Methods 연구자 : 이정준(07학번) 지도교수 : KAIST 여운승| 지도조교 : KAIST김근형, 김승훈 What is sound synthesis? Major sound synthesis methods • Sound synthesis is a process of generating sound from electronic equipments (analogue or digital) • Includes generation, combination, or mixing of sounds • The first experiment with computer-synthesized sound was done by Max V. Mathews in 1957 • Since then, dozens of sound synthesis techniques have been experimented • Sampling synthesis: • synthesized from pre-sampled audio data • Additive Synthesis: • established by the sum of elementary waveforms (e.g., sinusoids) • Subtractive Synthesis: • audio filters are used to shape the spectrum • Modulation Synthesis: • original signal is changed according to an aspect of a second signal • Physical Modeling: • Sounds are computed by a parametrized model of the physical sound source Modulation synthesis Newly proposed method • Modulation varies one sound waveform (‘carrier’) in relation to another waveform (‘modulator’) • More efficient in terms of parameter data, memory size, and computation time • In this research, we propose a new modulation method which uses a square wave with various settings as its amplitude modulator • similar to amplitude modulation • phase of carrier signal changes instantly by 180[deg] Ring Mod. (RM): creates two sidebands from two sinusoids Amplitude Mod. (AM): a pair of sidebands + carrier frequency Frequency Mod. (FM): two sinusoids result in a series of sidebands x = ? Experiment Results (1): mod. freq. • We used Pure Data (Pd) for sound synthesis[*] • In the Pd patch (fig. 1) • carrier oscillator • square wave generator • Signal analyzer • [*] http://crca.ucsd.edu/~msp Modulator: square waves waveform spectrum Carrier: sinusoid at 440[Hz] = 50 [Hz] x = 100 [Hz] = Fig. 1 200 [Hz] Results (2): duty cycle Conclusion • Many spectral peaks around the carrier frequency were shown in the experiment • Since an ideal square wave contains all odd integer harmonics, it produces complex spectra like FM • Therefore, by square wave modulation, we could generate a complex spectrum with only two input • Duty cycle of the modulator affects the timbre • We expect that this method could be used for synthesis of instrumental tones, generative music, etc. Modulator: square waves waveform spectrum Carrier: sinusoid at 440[Hz] = 0.5 x = 0.3 = 0.1 한국과학영재학교 http://www.ksa.hs.kr SoundLab, GSCT, KAIST http://soundlab.kaist.ac.kr