Ron Streicher addresses the NY Section, Sept 25, 2008.
Ron Streicher began his talk by quoting Richard Heyser's statement that "Stereo is merely the attempt to create the illusion of reality through the willing suspension of disbelief." Ron's lecture examined the history and development of the audio engineer's tools for creating that illusion. He made the distinction between monaural/binaural, which refer to transmitting sounds directly to the listener's ear(s) via one or two headphones, and monophonic/stereophonic, which refer to transmitting sounds to the listener via one or more speakers through the open air.
Spatial perception of sound depends upon intensity and time arrival. Contemporary and historical recordings were played to demonstrate how these factors can affect the apparent location of sounds within a stereo field.
The earliest work in this area was done in 1881 with numerous microphone "transmitters" at stage of the Paris Opera, each feeding dedicated telephone lines. These lines were terminated some 3km away at individual "receivers" (earphones). If a listener happened to pick up two earphones he could hear sounds which appeared to be spread out across the stage — at that time a revolutionary experience. Alas, no recordings were made of this experiment.
We heard examples of actual stereo recordings from the 1930s by Alan Blumlein in the U.K. and Harvey Fletcher in the U.S. — both of whom were unaware of the other's work. Fletcher developed the concept of three-channel sound recording and reproduction for motion-picture exhibition, which locked the dialog to a center speaker. This ensured that listeners who were not in the theater's "sweet spot" would correctly perceive the center-channel image. In 1940, Walt Disney's "Fantasia" used multiple speakers behind the screen as well as a number of surround speakers to create a sound track which enveloped the audience.
Other topics explained how the angle of arrival of sound and microphone polar patterns can be used to properly focus the primary sound field and balance direct to reverberant sound as well as controlling the width of a stereo recording even after a two-channel "mid-side" recording has been made. It is also possible to process the "side" channel to remove unwanted noise without affecting the "mid" channel pickup. A "mid-side" microphone pair can be used on a vocalist to provide a close pickup without plosive popping and low-frequency build-up ("proximity effect.")
The "Soundfield" micrpohone contains a number of elements which can yield a 5.1-channel image which is fully "steerable" in post-production. Ron also discussed "near-coincident pairs" of mics as well as the "Decca Tree" arrangement of three (or more) microphones suspended from a bar over the stage. As the mics are relatively close to each other they can be mixed down to stereo with minimum comb-filtering.
Multi-microphone techniques were examined, with the caveat that more channels can yield more creativity but also more chances for problems. Each mic must be carefully selected, mounted, cabled, tested and balanced against the other mics, each of which is connected to its own recording channel. "The cost of a project is proportional to the time it takes to do the job!"
Many informed questions were asked and answered throughout this lively evening.
Report by Joel Spector.
