Sound and acoustics are probably two words that you’ve probably come across before. Granted they’re quite the technical terms in fields like audio production but they’re still basic terms that almost anyone will encounter at one point or another.
It’s good to have a working definition of the terms in order to understand them better because most people don’t really know how they actually differ and why they’re used so closely together.
This post will discuss the fundamental difference between sound and acoustics because this is a question I encounter a lot in dealing with music producers.
With that said, What is the difference between sound and acoustics?
The main difference is that sound is the sensation perceived by the ear caused by the vibration or some other medium. Acoustics on the other hand deal with the way in which sound behaves in closed spaces. The acoustical properties of a room or space is the way in which sound behaves in that particular space.
In order to understand this topic properly we need to go through the elements of acoustics and the characteristics of sound.
The important elements in Acoustics are the sources and receivers of sound, the geometry of the closed space (room) and the materials (acoustic properties) of the walls.
Room Acoustics
Each and every space has a it’s own signature way in which if conducts sound.
This fingerprint of a space is unique according to the various properties of the space.
The fact that each and every space has its own unique way of handling sound means that acoustical engineers will always try to understand spaces in an effort to make them suitable for whatever they intend to use them for.
For example, classrooms should have good acoustical properties that allow for the good transmission of speech.
Recording studios also have to be designed in a special way so they can conduct sound like music without altering it.
Acoustical engineers always ensure that the spaces are treated acoustically in order to them suitable for recording, editing, mixing and mastering audio this is why you’ll find that most recording studios sound a certain way.
Sound Sources
Sound is produced by what we call sources, it is then modified by space and then finally picked up by the receiver.
Point Sources
This is where sound is said to be generated at any ideal point in space.
Point sources and their directivities can be used to pretty much represent most sound sources in real life.
For example, a person that is speaking has sound coming from the mouth… if we stand a few centimetres away we can term the sound source as point source.
Even loudspeakers are point sources if we are standing atleast a meter away.
Line sources
These are sources that carry sound in a line for example, a pipe carrying noisy flowing fluid or traffic noise from big high ways.
Surface sources
A surface source is simply a two dimensional line sources. In this case sound is radiated from a whole surface …
Some examples of these can be machines with vibrating surfaces which are not small enough to be simplified into point sources..
also noise from a crowd in a busy restaurant or a party.
Array sources
The last type of source used in room acoustics is the array source.
This is made up of two or more point sources next to each other.
Receivers
As long as you’re a human being, animal or any other organism that is able to perceive sound …you’re what is called a receiver.
To stretch it further, even electro-acoustic devices like microphones are also considered receiver’s.
They’re very useful because they pick up low frequency sounds inaudible for human ears. They are also useful in helping us convert signals into waves which we can then process.
Geometry
The geometry in this case refers to the basic room shape. The most basic room shape has 6 surfaces… Each and every surface contributes to the reflections that are heard in the overall sound source …
There are basically two types of sound reflections I.e. early and late..
At every reflection, part of the sound is absorbed from the wall and loses energy.
This continous loss of energy makes reflections weaker over time, until the initial sound from the source is fully absorbed at the walls.
An ideal wall that does not absorb any energy, would be called a rigid wall, while an ideal wall that absorbs all of the energy would be called a soft wall.
Materials
The materials basically refer to the material the particular space is made of…
Concrete walls are known to make sounds bounce from them… softer walls are known to absorb a bit of a sound ..
This is very important in acoustics.
Sound and Acoustics (Final Thoughts)
As you can easily tell Sound is the result of pressure variations, or oscillations, in an elastic medium
(e.g., air, water, solids), generated by a vibrating surface, or turbulent fluid flow.
The characteristics of sound are amplitude, frequency, Wavelength and velocity…
Amplitude is the measure of maximum pressure.
The frequency is the frequency (f) is basically the number of pressure variation cycles in the medium per unit time, or simply, the number of cycles per second, and is expressed in Hertz (Hz).
The Wavelength is simply the distance traveled by the pressure.
The velocity or time is simply the time taken for a cycle of a wave to pass a fixed point…
Acoustics on the other hand are the properties or qualities of a room or building that determine how sound is transmitted in it.
The key elements in Acoustics are the sources and receivers of sound, the geometry of the closed space or room and the materials (acoustic properties) of the walls.
Acoustics are important in studying the behavior of sound in a room.
