When it comes to recording sound it turns out there is an awful lot of things to consider. If you search for sound effects there are plenty of everything you could ever need from spinning tops to striking a match, both of which I have used in my own films and more recently audio books. Downloading royalty free clips isn’t necessarily always the easy option however.
Although a sound may sound realistic, because you filmed the real thing, it doesn’t mean it will fit in well into a sound scope. Manipulation of sound waves allows us to do lots of things to make a sound supposedly recorded in a bathroom for example sound different to that of a sound recorded in a concert hall. The key to the majority of successful sound editing to create something that sounds natural and as if you are in the room with the sound, this is known in the industry as Transparent sound reproduction.
Although there are endless possibilities with modern sound editing software such as Adobe Audition it is always best try to achieve the sound you are looking for at source, not during post production. If what you record is rubbish in the first place then unfortunately for us filmmakers no amount of editing will save it.
It’s easy to forget that sound on video, television, film, CDs etc is not natural. Even sound that sounds natural will have had some degree of artificial reverb. Sound producers also will have probably mixed the key sound with other sounds such as ambient noise to give the effect of transparency; Ambience sound is important in creating transparency and realistic sound. The ambience all around is generally inaudible but we hear it all the time so it is vital- too much is intrusive, too little is unnatural ‘dead‘.
Sound acoustics are what determine the way in which sound waves travel to our ears. The density of the sound is determined by texture – hard/soft surfaces, for e.g soft sounds within a bedroom where there are softer furnishings will sound significantly different to how sound can travel and bounce back in a bathroom where the furnishings are much harder.
Essentially how confined the sound source is to travel is what determines the sound of…a sound. These qualities can be manipulated through playing with reverberation acoustic ambience created by multiple reflections in a confined or enclosed space.
If we think back to the basic definition of sound as ‘waves of acoustic energy that disturbs the material that it passes through – typically air.’ It is also important to consider that when sound hits a surface more dense than air it reflects (in the same way as light) it moves in a different direction through the passage of time that energy is dissipated and becomes weaker until we can’t hear this effect anymore . Echo for example is an extreme form of a reverb which can be used to create this effect of sound being heavily reflected in a cavernous room. Although sound not hit us straight on and bounces back from a variety of different surfaces we rarely notice its existence unless its effects are extreme such as singing in the bathroom or under a bridge.
Reverb can also create an illusion of distance of a speaker or sound but microphones are nowhere near as sophisticated as our ears . This is why reverb is normally but not always done in post production artificially. It is possible to use hardware reverb units at source to capture reverbs of your choosing costing up to £10,000 which allows us to see a clearer idea of what the finished sound signal might sound like however a thing to consider is that a bad choice of reverb can destroy a good sound. Using reverb to increase the density of sound can be effective but can be easily overused unnecessarily and could leave actors within an audio play in some confusing spaces.
Some types of reverb we can play with in post production include:-
Early reflection– the amount of time it takes the initial sound wave to return the listener after it has hit and bounced off a surface. So in a small room with a very reflective surface there will be a very short early reflection. whereas in a cathedral there will be a much bigger one.
Decay the amount of time (measured in sec and ms) it takes for the sound to decay, sometimes used to create transparent sounds and sometimes for dramatic effects.
Delay– a severe or exaggerated form of reverb. The time difference between the initial sound signal and reflection exaggerated to .5 of a second and beyond.
Used extensively in music production to create some very interesting sonic effects. Often the delay is matched to the beats per minutes.
Panning– to create impression of space or spatiality in a recording usually where there are numerous sounds sources. Can be used particularly effectively to create an effect that a sound source is moving.
Esoteric effects – doppler, ring modulation, vocoding, auto tune – extreme forms of reverb that are not as common in works aiming to be realistic but rather music.
There is a lot more to sound than meets the ear. If you want to see how I have put this new knowledge into practice check out my new series of audio books for children. Thanks