Sound for Moving Image Workshop Lecture - Binaural Panning in Logic Pro X PDF

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Summary

This PDF file contains lecture notes taken during a Sound for Moving Image Workshop Lecture , and share details on how to operate the Binaural Panning Mixer in Apple's Logic Pro X
The Lecture was lead by Dr. Andrew Dolphin.
Term 1, 2017/2018
University of Portsmouth....

Description

Binaural Panning in Logic Pro X

Techniques and Uses 2017 An important part of mixing audio signals is the placement of individual sound sources at different spatial positions. Most common recording and mixing techniques simply send a given signal at different levels to the available loudspeakers—two for stereo, or more for quadraphonic or surround setups—to create a virtual sound stage. This approach is somewhat flawed, however, as human beings are able to locate sound sources at different positions with just two ears. Virtually all spatial information for all sounds is included in the two signals arriving at the two eardrums. From these signals, human beings can determine characteristics such as inter-aural time, level differences, and—based on the listening experience—information about the spatial origin of the sounds being heard. Are they coming from in front or behind, from the left or right, from above or below? This ability to perceive where a sound originates from is referred to as binaural hearing. In theory, the spatial positioning of any sonic experience can be reproduced during playback, so no special techniques need to be employed during recording. There is, however, one drawback to

this approach: every person has differently shaped ears and different body and head proportions, all of which influence the way sound signals arrive at the eardrum—not to mention aspects such as hearing loss, subjective responses to the sounds being heard, and so on. Given these physical differences, each person listening to the same sound source, while standing or sitting in the same position, will hear slightly different binaural signals. Therefore, perfect reproduction would only be possible if you could make a recording with tiny microphones placed inside your auditory canals. Because this is impractical, binaural hearing has been emulated in sound laboratories by using mannequin heads with built-in microphones. This approach has led to binaural recordings to fit the average person, which are more or less compatible with the way most people hear. Playback of binaural recordings is best suited to headphones, ideally combined with signal conditioning (processing) that ensures the signals are accurately reproduced. Given a specialized listening environment, it’s also possible to reproduce these signals with loudspeakers, utilizing a process known as crosstalk cancellation. As you are unlikely to have the technology required to make binaural recordings, your best chance of simulating binaural signals is by processing the sound signal on playback. This is known as the head-related transfer function (HRTF), which approximates the change that a signal undergoes on its way from the source to the eardrum. The Binaural Panner is available when Surround is selected in the Advanced preferences pane.

By setting the channel strip’s output to Binaural, you can use the Binaural Panner to position the signals on the panning plane. The signal that results from using the Binaural Panner is best suited for headphone playback. You can, however, process the Binaural Panner output using the Binaural Post-Processing plug-in, which allows you to play back the binaural pan effect through loudspeakers. You control the panning effect in the Binaural Panner by positioning the panning pucks on the panning plane at the top of the window, and by adjusting some additional parameters. These are the window’s main elements: Pucks Panning plane 3D image Size field Mode buttons Doppler button Click to show the Extended parameters. • Angle, Elevation, Distance: Information fields that adjust automatically when changes are made to the puck positions. • Spread: Information field that adjusts automatically when changes are made to the puck positions. You can also interact directly with it by dragging its numerical value. (Making changes here also affects the left and right puck positions.) • Panning plane: Area for positioning the signals —using the pucks—in the stereo image. • Pucks: Used for positioning the signals on the panning plane—pan and direction. Chapter 16 Mix a project 522 Open the Binaural Panner 1 Click-hold the channel strip’s Output slot (on mono or stereo channels), then choose Binaural from the pop-up menu. The Binaural Pan control replaces the Pan knob. 2 Double-click the Binaural Pan control to open the Binaural Panner.

Control the binaural pan position 1 Drag the left or right puck (panning pucks) to make the stereo image wider or narrower. The pucks also work on a second axis—up and down— relative to the third puck. 2 Drag the third puck (the direction puck) to determine the forward and backward direction. As you adjust the direction puck, the two panning pucks move accordingly. The Angle, Elevation, Distance, and Spread values also change. 3 Select the Mode (virtual shape) of the planning plane: • If set to Planar, the panning results are shown on a flat circular plane. Chapter 16 Mix a project 523 • If set to Spherical, the results are placed on a virtual sphere. If it helps, imagine the sphere as a virtual head. When the direction puck is placed in the top half of the circular plane, the sound is in front of the listener. As the direction puck is moved toward the lower half of the plane, the sound passes up, and over your head, and ends up behind you. 4 Set the size of the plane or sphere by doing one of the following: • Drag the Size field value up or down. • Double-click the Size field, then enter a new value. • Option-click the Size field to reset it to its default value (1.50m). 5 Click the Doppler button to turn on or off the Doppler effect. 6 Select the Diffuse-Field Compensation checkbox in the Extended Parameters area to ensure a neutral sound for headphone playback, utilizing diffuse-field compensation. Note: When using multiple Binaural Panners on several channel strips, turn this option off and route the output of the Binaural Panners to an aux channel strip, in which you insert the Binaural

Post-Processing plug-in. The Binaural PostProcessing plug-in allows you to apply diffusefield compensation to all Binaural Panner outputs at once, saving CPU power. 7 If in Planar mode, use the Extended Parameters sliders to control the vertical offset and tilt of the circular plane. Watch the 3D image when changing them to get a clear idea of their functions. Chapter 16 Mix a project 524 Use the Binaural Post-Processing plug-in The Binaural Post-Processing plug-in is available in aux and output channel strips. This plug-in allows you to apply various compensation modes on a stereo bus or output, through which several, or all, binaural signals are routed. This saves CPU power and makes it easy to switch between compensation modes. For full details about this plug-in, see the Logic Pro Effects manual....