When you watch a movie or listen to music part of the entertainment value, beyond the melody and story, is the environment that you create within the sound track. A lot of times when you want to create the effect of a large space on a voice or footsteps in that space you must employ some simple techniques to make the sounds inside that space more believable. These effects can be heard in stereo and in surround sound systems that are used to enjoy being immersed into a story or environment.
In the case of stereo effects these environments can be created by using a slight delay between the two stereo speakers and the audio signal that is fed to them. In the extreme cases such as rock and roll songs you might hear one guitar sound in the left side of the field, the other guitar sounds in the right side of the stereo field and the drums and bass sounds closer to the middle of the stereo field. This is a common mixing technique that is used in a lot of audio recordings and is easy to re-create with a few simple tools that are included in most recording software systems and digital audio workstations.
The most basic tool is the “pan” tool. The pan tool can send an audio signal that was recorded in mono to one side or the other of a stereo field. While in mono the audio signal can be equally distributed to both sides of the stereo field or panned either left or right completely or in in small increments giving the effect of slightly to your left or right in the stereo field. In the case of a band application the rhythm guitarist might record his guitar part twice and then pan each track wide to the left and right sides of the stereo field. This is two separate recordings of exactly the same guitar part but the slight differences will create a very lush and wide guitar sound that seems to be more powerful that in actually is. This technique works best for vocals or other instruments that use the mid-to-high frequency ranges while bass and drum frequencies are best kept at the center or mono positions because of their low frequencies. This can help the low frequencies remain clear instead of spread out and muddy sounding.
In the case of the Foley artist a sound can be panned from left to right within the stereo field in order to simulate movement such as the sound of a car passing by from left to right on a movie screen. The audio is just as important as the visual aspects of a movie because it helps the person watching the movie become immersed in the story, the environment and gives a nice sense of realism to the overall finished project.
Another technique used to create a stereo field from a mono audio signal is the use of a delay effect. The mono audio signal can be split into a left and right signal and then distributed into the stereo output. This can be done by adding a very slight delay to one side of the field that creates a widening effect and can be used to create an ‘air” effect that simulates a small room or an open space for the audio signal.