In answering the question “What is sound?” several answers can be given. You may say a sound is a vibration. A sound can be interpreted as an acoustic wave, aka a sound wave, which can be transmitted by gas, liquid, or solution. It may be described as receiving sound waves and how it is perceived by the brain.
Sound, sound waves, and sound energy are terms used interchangeably to assign a definition and explanation to sound but there is much more to sound than simply basic definitions. There is endless content to unpack when it comes to understanding sound, how sound is generated, and how we perceive sound. Let’s start with the basics.
What Is Sound?
To the extent that our senses allow us to perceive the world around us, sound is something that can be heard while being invisible. Going by our senses alone, this is totally true. However, the physical world operates through laws that transcend our senses. By these laws, sound is tangible in a way that is not strictly audible. Sound has a visceral conception, behaves in erratic ways, travels a certain distance, and then dies.
Consider the base definition of sound to be a pressure wave created by a vibrating object.
What Is A Sound Wave?
A sound wave is a pattern of disturbance accomplished by a movement of energy traveling through a medium, i.e. air, water, etc. As we analyze the science of sound, one can dig into details like the loudness or amplitude, the pitch or frequency, and other key characteristics that help us human beings define everything we hear.
Though we aren’t equipped to see sound this way because we think it to be an auditory element, try to imagine what a sound wave looks like.
Here’s an exercise that will help you envision the physical manifestation of sound. Picture you’re on the shore of a lake, throwing rocks into the water. Once a rock impacts the lake, layers of waves are produced along the water’s surface. The shape and frequency of the waves depend on the density of the water and the force with which the rock penetrates it. In this case, that varies based on the weight of the rock and the height of the drop.
Take this same concept and apply it to the sounds we make with our vocal cords. When a sound is made, its pressure penetrates the air around it, and literal, tangible waves are created, very much like the waves along the surface of the lake. How loud the sound is and how far it travels is based on the amount of pressure created during its inception. The human senses don’t perceive these waves visually, but they’re there.
Give science a little more time and we will most likely, one day, have some form of visual aid that will allow us to see what a sound wave is as one occurs. In this respect, music could be listened to (and seen) in a completely new way.
What Is Sound Energy?
When we are talking about sound energy, it is no different from what we have already described discussing sound and sound waves.
The energy is what creates the sound waves and the aforementioned pattern of disturbance. Energy creates vibrations between molecules. As the molecules bump together, widespread vibrations increase, resulting in the chain reaction of a sound wave. The wave continues until the molecules run out of all available energy.
Though it may seem quiet in the small space around you, you can find sound energy anywhere and everywhere. There may be someone honking a car horn a few miles away, and that sound might get mangled with the symphony of buzzing from a bee hive, before travelling into and out of apartment building windows, where people gargle their mouthwash and such, and that snowballing sound will absorb nameless additional input before reaching you in your space.
These effects are all examples of sound energy, whether that is everyday sounds or a DJ spinning house music.
Sound is like light in a lot of ways. It has a specific point of conception and travels outward from that point based on the strength of its emission. A night light will cast a dim glow into its immediate vicinity, while the sun will emit light for immeasurable distances in every direction. The same applies to sound, whether the source is a person clearing their throat, or the sound of thunder booming.
The clear difference between the two is that light can be produced in a theoretical perfect vacuum (a space entirely void of matter; total nothingness) whereas sound requires a medium (such as air, water, metal, or glass) to travel through.
How Does The Brain Perceive Sound?
The aspect of sound that directly concerns us is its physiology. In other words, how our ears receive the sound and how our brains perceive it. When a sound wave reaches the ear, it influences the eardrum through pressure.
Every sound wave is infinitesimally complex, and its output creates any number of low-pressure and high-pressure regions in the air around it. Upon arriving at the ear, a high-pressure region pushes the eardrum inward, while a low-pressure region pulls it outward. This happens at varying speeds and frequencies, and the overall effect results in the discernment of the various sounds in our environment. The sound wave is then transmitted through the middle ear to the inner ear until it reaches the brain for interpretation. This is how we hear sound.
What’s also interesting to note is that, given our physiological composition, our ears are not equipped to pick up every sound frequency available to us. For example, it’s commonly understood that dogs are able to hear high frequencies that reach our ears as total silence. Comparatively, elephants communicate with each other across great distances through extremely low frequencies that we are equally deaf to.
We may only hear a fraction of what’s around us at any given time but regardless, sound, sound waves, and sound energy form a massive part of our universe.