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Home , Microphone, Phonograph, Pitch correction

Edison Revisited by Scott Cannon

Advisors: Dr. Jonathan Berger and Dr. Julius Smith

Stanford Electrical Engineering 2002 Summer REU Program

Scott Cannon- 2002 EE REU Program Edison Revisited Background

The first was developed in 1877 as a result of 's research on two other , the telegraph and the . By 1908, the Edison Phonograph could play four minute recordings from 2 inch diameter wax cylinders which rotated at 160 rpm. The were hand- cranked, and used for recording and business dictation purposes.

Scott Cannon- 2002 EE REU Program Edison Revisited Background

A collection of more than 1500 original cylinder recordings, and two fully functional were recently donated anonymously to Stanford University for use as an educational Photo: an early recording session, tool, and to be enjoyed circa 1900 by anyone via the internet.

Scott Cannon- 2002 EE REU Program Edison Revisited Goals

The Edison Project focused on achieving two primary goals:

1) Digital encoding and preservation: To develop an efficient, high-fidelity means of capturing, processing, distributing, and preserving a collection of more than 1500 original Edison Cylinder recordings. 2) Audio Restoration: To research and design high-quality algorithms for removing artifacts that are inherent to 90 year old recordings.

Scott Cannon- 2002 EE REU Program Edison Revisited Part I: Method

In Part I, research was focused to determine the best means of capturing and processing the audio from the phonograph. Every step of the chain was examined and constructed to maintain the highest fidelity.

Focus of Part II

Phonograph AD Conversion Processing The Internet -The signal begins - Over a dozen -All capture was -A was Each recording Recordings were with an original hand- of done at 44.1 kHz, used for received a mix of: converted to .MP3 cranked Edison various pickup and 16 bit (CD flexibility format for internet phonograph, nearly patterns were quality) -Digital editing -Noise reduction distribution, and 100 years old. auditioned in -Selected was completed -Click removal cataloged in a -In addition, our different recordings were with Wavelab, - detailed database research also locations around captured using 24 Matlab, - at CCRMA. explored the use of the phonograph. bit encoding at 48 SoundForge, professional cylinder kHz, for and Protools -Adjustments for players using today’s . eccentricity . - compression Scott Cannon- 2002 EE REU Program Edison Revisited Part I: Results A wide array of tests examined each component in the signal chain to create the best combination of equipment and tools. For example, it was discovered, that a stereo microphone configuration placed 1.5 meters from the phonograph captured 5 dB less noise (around 1730 Hz) than a high-proximity microphone at 10 cm. Response

Mic 10cm away While this configuration helps to mitigate noise, the stereo recordings felt more distant to some listeners, who Mic 1.5 meters away preferred a close microphone with acoustic dampening.

Scott Cannon- 2002 EE REU Program Noisy Edison Revisited Part I: Results

Analysis showed that the Frequency Content of Captured phonograph produced no significant content above 4 kHz. In addition, content below 80 Hz Amplitude was negligible. Thus data (dB) compression algorithms and a bandpass filter were selected to

deliver only the relevant content ) c e to the listener, resulting in a s (

e smaller file size for faster m i T distribution over the web. Frequency (Hz)

The final system integrated the results of these and many other measurements at all points in the signal chain to capture the highest quality sound possible.

Scott Cannon- 2002 EE REU Program Edison Revisited Part II: Method

Part II of this research project aimed to develop a novel method to reduce the “pops” and “clicks” (very brief caused by dirt and scratches) that are inherent to phonograph recordings.

These signal distortions are eliminated through two primary processing steps: 1) Detection of the signal distortion. 2) Replacement of the distorted sound with an interpolated estimation.

Scott Cannon- 2002 EE REU Program Edison Revisited Part II: Results

Matlab was used to create algorithms that Original, distorted waveform effectively detect substantial distortions, and splice good data Distortion detected and removed from surrounding areas such that there are no signal discontinuities in the New, interpolated waveform new waveform. Amplitude (db)

The results sound Time (ms) very good! Problem Area

Scott Cannon- 2002 EE REU Program Edison Revisited Discussion

While our algorithms for removing distortion performed well for distinct artifacts in the waveform, the ability to remove more subtle forms of audible distortion proved elusive with these methods. Future research will attempt to develop similar methods based on minimum variance estimation under various modeling assumptions to more effectively “clean up” old analog recordings.

Scott Cannon- 2002 EE REU Program Edison Revisited Conclusion

This research project accomplished two goals: Digital encoding and preservation: An efficient, high-fidelity means of capturing, processing, distributing, and preserving a collection of more than 500 original Edison cylinders was developed. Files are posted at http://ccrma-www.stanford.edu/groups/edison/

Audio Restoration: A method for removing signal distortion was created. A foundation has been built on which to develop more robust algorithms.

Scott Cannon- 2002 EE REU Program Edison Revisited References

Godsill, Simon J. and Rayner, Peter J.W. Restoration. 1998. Springer, London.

Oppenheim, Alan V. and Willsky, Alan S. and Systems, Second Edition. 1997. Prentice Hall.

Lockhart, G. B. and Goodman, D. J. Reconstruction of missing speech packets by waveform substitution. In: Signal Processing 3: Theories and Applications. 1986.

Garbit, Frederick J. The Phonograph and its Inventor, Thomas Alva Edison. 1994. Gunn, Boston.

Scott Cannon- 2002 EE REU Program Edison Revisited