Sound Effects, Sound Libraries and the "Doppler Effect"

Sound effects and sound libraries are used all over films and it is pretty much guaranteed that there will be at least one instance of this in every film and TV show you watch.

Jack Foley is widely known as the initial founder of adding post-production sound effects to film. The reason this process takes place is because some sound effects could be hard to record on-set and need to be more distinguished, need to be taken from the sound of something else or need to be edited to achieve the desired sound. People who record sound effects separately from the film are known as "Foley artists".

Here is an excellent example of Foley artists using many different things to emulate sounds from a film.

You can see that they are experimenting with many different objects to achieve a fitting sound for the movie, whilst watching the film to keep it in time.

An example of a sound being taken from somewhere else is the process used to create the laser blast sound from George Lucas' "Star Wars" movies. Sound designer Ben Burtt climbed a radio tower and used a hammer to strike one of the guide wires whilst recording it to produce this famous sound.

Another example of this lies in Peter Jackson's "The Lord of the Rings: The Fellowship of the Ring". David Farmer, who is the sound designer for the Lord of the Rings movies, used a cinder block scraping along a wooden floor at varied speeds to create the sound of the Balrog's movement, and the crackling sound which accompanies the roar of the creature is created using a mixture of rocks crashing together.

 

Ben Burtt (mentioned previously), who is the sound designer for the Star Wars movies, used a very interesting method for creating the famous sounds of the lightsabers in the films, as explained in the following video.

The sound of the lightsaber moving when a microphone is waved past the sound source is created by the scientific principal known as the "Doppler Effect". This is the apparent change in the frequency of a wave caused by motion between the sound source and the observer.

For example, if you were to stand at the side of a road and a car drove past you, the sound waves given off by the car as it approaches are compressed against the front of the car making it appear to be higher pitched. Then when the car passes, the sound waves at the back of the car are flowing off of it and are spaced further apart, making the sound appear to be lower in pitch.

 

This is a visualisation of a sound wave. The further apart the waves are, the lower the sound, and the closer together the waves are, the higher the sound.

Here is a video of the practical experimentation of the Doppler Effect using the example I explained earlier.