From: Kathleen M. Wong, UC Berkeley
Published August 21, 2007 01:35 PM

Using Hi-Tech Tools To Rescuing Recorded Sound from Silence

Berkeley, California - While listening to National Public Radio in 2000, Carl Haber learned that the Library of Congress had a big problem. The Library's audio collection, which spans the 130-year history of recorded sound, includes the soaring tenor of Enrico Caruso, the speeches of Teddy Roosevelt, and the voices of Native Americans from now-vanished tribes. These echoes of a bygone era were recorded on media such as wax cylinders and shellac and lacquer discs. But many are now too fragile to play in their original format; the pressure of a stylus or phonograph needle could cause irreversible damage. Others are too broken, worn or scratched to yield high-quality sound. The archivists needed a means to preserve the recordings without injuring them further.


A physicist with Lawrence Berkeley National Laboratory (LBNL), Haber was developing subatomic particle detectors to be used at CERN in Geneva, Switzerland. This involved using digital cameras and robots to place each delicate detector in precisely the right place. In a flash of insight, Haber realized that an optical scanning system could solve the Library's quandary.


Millions of historical sound recordings such as this wax cylinder are in need of preservation in the United States alone. credit: courtesy Carl Haber


"I had phonograph records as a kid, so I knew sound was stored in a mechanical profile. I realized that we could use images to figure out in detail what the groove actually looked like, and use a computer to calculate the sound. I thought that might be a way to get around the problem of things being delicate and damaged; you wouldn't have to touch them," Haber says.


Haber already had access to a machine that could make high-resolution digital scans. Postdoctoral fellow Vitaliy Fadeyev wrote a computer program to control the turntable and translate the images into sound.


ADVERTISEMENT

Haber used a narrow beam of light to illuminate the record's surface. The flat bottoms of the grooves and the spaces between tracks appeared white; the sloped sides of the grooves, scratches and dirt looked black. The image was then analyzed by computer. The program found the edges of each groove by focusing on areas of high contrast. It could correct areas where scratches, breaks or wear made the groove wider or narrower than normal.


A digital scan of phonograph grooves taken by IRENE. The side-to-side wiggles of the groove contain the audio information. credit: Carl Haber


That first test was agonizingly slow. Forty minutes of scanning was required to obtain just one second of audio. But it provided what the scientists needed-proof of principle. And the scan played far more cleanly and clearly than the worn original disc.


Haber and Fadeyev wrote a paper describing the device and sent it, unsolicited, to the Library of Congress. The next thing Haber knew, he had an invitation to visit the Library to talk about the technique. By 2004, Haber and Fadeyev were developing ways to scan discs and cylinders more efficiently.


The two types of media presented very different problems. On antique monaural discs, sound is recorded in horizontal wiggles of the record groove. On cylinders, sound is recorded in the vertical plane-the depth of the groove.


The completed digital phonograph scanner, named IRENE, installed at the Library of Congress. It was developed with funds from the Library of Congress, the National Endowment for the Humanities, the National Archives, and the Mellon Foundation. credit: courtesy Carl Haber


"With discs, we used a camera to image them at high resolution in two dimensions. Once we understood how cylinders were recorded, we realized we had to measure the third dimension (3D) as well," Haber says.


In 2005, LBNL engineers Earl Cornell and Robert Nordmeyer joined the project. With the Library's urging, the team concentrated on producing a dedicated disc scanner. Dubbed IRENE (after the Weavers' "Good Night, Irene," the first disc the team scanned), the device was installed at the Library last summer for evaluation and needs just four seconds to scan one second of audio.


The group is now refining a device that scans in 3D. The device is based upon a type of confocal microscope. White light directed at the surface of a cylinder or disc passes through a lens. But the lens is imperfect by design; though it splits the light into its component colors, each color comes into focus at a different depth. The color of the reflected light reveals the height of the scanned point. The computer assembles these points into profiles for each groove and translates the data into sound.


A digital scan of phonograph grooves taken by IRENE. The side-to-side wiggles of the groove contain the audio information. credit: Carl Haber


The current 3D scanning process takes 20 hours to record one minute of sound. But a new version of the confocal scanner, developed for the dental industry, should reduce that to about 10 minutes.


A half-dozen physics and engineering undergraduates from UC Berkeley have been instrumental in speeding the project along. "Students can apply the kinds of techniques they learn in classes about statistics, mathematical analysis and signal processing to a project they can really get their arms around," Haber says. A Berkeley graduate student in linguistics is poised to join the project later this summer.


UC Berkeley's Phoebe Hearst Museum and Native Americans are among those who could benefit the most from IRENE and its sister 3D scanner. In the early 1900s, UC Berkeley anthropologist Alfred Kroeber and colleagues recorded the legends, songs, customs and voices of dozens of California Indians on some 3,000 one-of-a-kind wax cylinders. Many of these tribes and languages have since died out or are on the verge of extinction. The LBNL group is now collaborating with linguist Andrew Garrett and Victoria Bradshaw of the museum to digitize the Kroeber recordings. Remastering these cylinders could help new generations of native peoples study their ancestral customs and tongues—and help carry the sounds of the past into the future.


Sound Samples


* "Chattanooga Blues" (Ida Cox, Paramount 12063, 1923). IRENE is largely able to overcome the loud distortions caused by severe stylus damage on this worn, 78 rpm shellac disc.


stylus version


IRENE version


* Haber and colleagues are now scanning one-of-a-kind wax cylinder recordings of California Indians made in the early 1900s by UC Berkeley anthropologist Alfred Kroeber and colleagues. The cylinders are no longer played by stylus to prevent wear.


This recording features a song sung by Ishi of the Yahi tribe circa 1911-1913.


Related Web Sites


* IRENE


* Recent examples of IRENE sound scans


* "You can play the record, but don't touch." by Nell Boyce. Morning Edition, National Public Radio, July 16, 2007


* "Digitizing the voices of the past," by Keay Davidson, San Francisco Chronicle, July 12, 2004


* "Playing Old Records (No Needle Required)," by Anne Eisenberg, New York Times, May 6, 2004


Terms of Use | Privacy Policy

2014©. Copyright Environmental News Network