Julius Smith

Julius O. Smith III
Born	Julius Orion Smith III 1953
Nationality	American
Alma mater	Rice University  (B.S., 1975) Stanford University  (M.S., 1978; Ph.D., 1983)
Known for	Digital waveguide synthesis Shazam audio fingerprinting Closed-form spatial localization Windowed-sinc sampling-rate conversion Sines+noise additive synthesis
Awards	Fellow, Acoustical Society of America (2003) Fellow, Audio Engineering Society (2008) Richard C. Heyser Memorial Lecturer (2006)
Scientific career
Fields	Digital signal processing Music technology Computer music
Institutions	Stanford University (CCRMA) NeXT Computer (1986–1991)
Thesis	Techniques for Digital Filter Design and System Identification with Application to the Violin  (1983)
Doctoral advisor	Gene F. Franklin
Website	ccrma.stanford.edu/~jos/

Julius Orion Smith III (born 1953) is an American educator and engineer who is Professor Emeritus of Music and, by courtesy, Electrical Engineering at Stanford University's Center for Computer Research in Music and Acoustics (CCRMA). ^[1] He is known for pioneering digital waveguide synthesis, a physical modeling technique adopted in commercial instruments such as the Yamaha VL-1 synthesizer. ^[2] Smith is also co-inventor of the core audio-fingerprinting algorithm behind the music-identification service Shazam. ^{[3] [4]}

Education

Smith earned a B.S. in electrical engineering from Rice University in 1975 and M.S. and Ph.D. degrees in electrical engineering from Stanford University in 1978 and 1983, respectively. His doctoral dissertation, supervised by Gene F. Franklin, was entitled Techniques for Digital Filter Design and System Identification with Application to the Violin. ^{[1] [5]}

Career

Early career and NeXT

From 1986 to 1991, Smith was a founding member of the Sound and Music Group at NeXT Computer, where he developed real-time signal-processing software for the Music Kit, Sound Library, and other audio software for the NeXTSTEP platform. ^{[6] [7]}

Academic career

Smith joined the Stanford faculty in 1991, becoming an associate professor in 1994, full professor in 2004, and professor emeritus in 2022. ^[1] At Stanford, he has taught courses in digital signal processing, computer music, and acoustics, while mentoring numerous graduate students who have gone on to careers in academia and industry.

He has held visiting appointments at the Télécom Polytechnic Institute of Paris, IRCAM Scientific Council in Paris, and Helsinki University of Technology, where he collaborated closely with Finnish acoustician and engineer Matti Karjalainen. ^[8]

Industry involvement

Beyond academia, Smith has worked with several audio-technology companies, including:

• Staccato Systems – developed physical modeling synthesis technology licensed by Analog Devices
• Shazam Entertainment – co-invented the core audio fingerprinting algorithm ^[3]
• moForte – continued development of physical modeling technologies ^[9]

Research contributions

Digital waveguide synthesis

Smith's most influential contribution is digital waveguide synthesis, a computationally efficient method for simulating the physics of musical instruments. This technique models wave propagation in strings, tubes, and membranes using digital delay lines and filters. His 1992 Computer Music Journal article formalizing this approach remains a foundational text in the field. ^[10]

Spatial localization

Smith's 1987 paper "Closed-Form Least-Squares Source Location Estimation from Range-Difference Measurements" introduced an algebraic solution to the time-difference-of-arrival (TDOA) localization problem. This work has been cited over 1,000 times and is fundamental to applications in radar, sonar, and wireless communications. ^[11]

Sampling-rate conversion

At ICASSP 1984, Smith introduced windowed-sinc interpolation for high-quality, time-varying sampling-rate conversion. This method has been widely adopted in commercial sample-rate converters ^[12] and open-source software such as libsamplerate. ^[13]

Educational contributions

Smith has authored four open-access textbooks that are widely used in graduate-level audio DSP courses: ^[14]

• Mathematics of the Discrete Fourier Transform (2007)
• Introduction to Digital Filters (2007)
• Physical Audio Signal Processing (2010)
• Spectral Audio Signal Processing (2011)

Honors and recognition

• Fellow, Acoustical Society of America (2003) – "for applications of digital signal processing to musical acoustics" ^[15]
• Fellow, Audio Engineering Society (2008) – "for research contributions in, teaching of, and service relating to digital audio signal processing in music" ^[16]
• Richard C. Heyser Memorial Lecturer, AES 121st Convention (2006) – delivered lecture on "History and Practice in Digital Sound Synthesis" ^[17]
• Ranked among the world's top electronics and signal-processing researchers by Guide2Research (2020) ^[18]

Selected publications

Books

• Smith, Julius O. (2007). Mathematics of the Discrete Fourier Transform (DFT): With Audio Applications (2nd ed.). W3K Publishing. ISBN   978-0-9745607-4-8.
• Smith, Julius O. (2007). Introduction to Digital Filters: With Audio Applications. W3K Publishing. ISBN   978-0-9745607-1-7.
• Smith, Julius O. (2010). Physical Audio Signal Processing: For Virtual Musical Instruments and Audio Effects. W3K Publishing. ISBN   978-0-9745607-2-4.
• Smith, Julius O. (2011). Spectral Audio Signal Processing. W3K Publishing. ISBN   978-0-9745607-3-1.

Key papers

• Smith, Julius O. (1992). "Physical Modeling Using Digital Waveguides". Computer Music Journal. 16 (4): 74–91. doi:10.2307/3680470. JSTOR   3680470.
• Smith, Julius O.; Abel, Jonathan S. (1987). "Closed-Form Least-Squares Source Location Estimation from Range-Difference Measurements". IEEE Transactions on Acoustics, Speech, and Signal Processing. 35 (12): 1661–1669. doi:10.1109/TASSP.1987.1165089.
• Smith, Julius O. (1983). Techniques for Digital Filter Design and System Identification with Application to the Violin (Ph.D. dissertation). Stanford University.

See also

• Center for Computer Research in Music and Acoustics
• Digital waveguide synthesis
• Physical modeling synthesis
• Shazam (application)

References

1. "Julius Smith – Stanford Profiles". Stanford University. Retrieved 28 June 2025.
2. Ressner, Jeff (March 1994). "Wave of the Future". Wired . Retrieved 28 June 2025.
3. US 6990453,Avery Li-Chun Wang; Julius O. Smith III,"System and methods for recognizing sound and music signals in high noise and distortion", assigned to Shazam Entertainment Ltd. 
4. "How Shazam Makes Unique Audio Fingerprints to Identify Songs". The Wall Street Journal . June 2023. Retrieved 29 June 2025.
5. "Julius Smith – Hertz Foundation Fellow profile". Hertz Foundation . Retrieved 28 June 2025.
6. Smith III, Julius O.; Jaffe, David A.; Boynton, Lee (May 14–17, 1989). "Music System Architecture on the NeXT Computer". The Proceedings of the AES 7th International Conference: Audio in Digital Times. Toronto, Canada: 301–312.
7. "Music/Audio Signal Processing – Julius O. Smith III". DSPRelated.com. 2008. Retrieved 28 June 2025.
8. Bilbao, Stefan (2019). "Physical Modeling, Algorithms and Sound Synthesis: The Work of Julius O. Smith III". Computer Music Journal . 43 (2–3): 15–38. doi:10.1162/comj_a_00516.
9. "moForte Audio Modeling". moForte Inc. Retrieved 28 June 2025.
10. Smith, Julius O. (1992). "Physical Modeling Using Digital Waveguides". Computer Music Journal . 16 (4): 74–91. doi:10.2307/3680470. JSTOR   3680470.
11. Smith, Julius O.; Abel, Jonathan S. (1987). "Closed-Form Least-Squares Source Location Estimation from Range-Difference Measurements" . IEEE Transactions on Acoustics, Speech, and Signal Processing . 35 (12): 1661–1669. doi:10.1109/TASSP.1987.1165089 . Retrieved 28 June 2025.
12. Smith, Julius O.; Gossett, Phil (1984). "A Flexible Sampling-Rate Conversion Method". Proceedings of the IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP). Vol. 2. pp. 19.4.1–19.4.2. doi:10.1109/ICASSP.1984.1172555.
13. Erik de Castro Lopo. "Secret Rabbit Code (libsamplerate)" . Retrieved 28 June 2025.
14. Roads, Curtis (1996). The Computer Music Tutorial. MIT Press. p. 510. ISBN   978-0262680820.
15. "Fellows of the Society". Acoustical Society of America. Retrieved 28 June 2025.
16. "AES Awards – Fellowship Award Recipients". Audio Engineering Society. Retrieved 28 June 2025.
17. "Richard C. Heyser Memorial Lecture: Julius O. Smith III". Audio Engineering Society. Retrieved 28 June 2025.
18. "Julius O. Smith – Guide2Research Ranking Profile". Guide2Research. Retrieved 28 June 2025.

External links

• Official website
• Complete bibliography
• Google Scholar profile
• Video lectures and presentations