How Does Sound Travel in a Room
Like heat, electricity, and nuclear radiation, sound is a form of energy. Sound energy begins as motion that vibrates particles in the surrounding medium (generally air) to produce the noises we hear on a daily basis.1
Air isn’t the only medium sound can travel through, however. Anyone who has stayed in an apartment building or next to a busy street knows sound is constantly penetrating walls to make its way into our living spaces.
But how does sound travel in a room, and how can we prevent it from disturbing our personal space? This guide will explore the basic science of sound and offer some key soundproofing tips to keep your home quiet and peaceful.
Basics of Sound Waves
Sound is invisible, but if you could see it, it would appear as oscillating waves emanating from the source. Sound waves are produced via vibrations, so when you hear someone bang a drum or yell aloud, what you’re really hearing is a series of vibrations making their way to your ears.
These sound waves enter the ear canal and, in turn, vibrate our eardrums and, eventually, our cochlea—the part of the ear responsible for catching and interpreting sound. The cochlea then sends these sound signals to our brains, where they’re interpreted for information.2
How the cochlea interprets sound is based on the characteristics of its waves. For humans, this is interpreted as volume and pitch. But, to consider sound waves scientifically, we must understand their3:
- Frequency – Frequency is a measure of how many sound waves pass a certain point in a given period of time. Seconds are the most common timeframe to utilize and provide us with the useful hertz (Hz) scale of measurement. One Hz is equal to one soundwave passing a point every second.
- Wavelength – Wavelength is the distance from the highest point in a sound wave (the crest) to the lowest (the trough). It tracks how far sound spreads across an enclosed space and, since it’s a measurement of distance, is usually expressed in meters or feet.
- Amplitude – Amplitude is a measurement of the distance from a sound wave’s center point to either the crest or trough. It’s likewise measured in meters or feet, and the further the distance, the more energy a sound wave carries (i.e., how loud it is).
How Sound Travels in Air
When you speak, clap, or make any other sort of noise, what you’re really doing is disturbing the stillness of an empty space. The vibrations from your hands or vocal box cause pressure fluctuations in the air around you. These fluctuations occur both upward (condensations) and downward (rarefactions) and disrupt tiny, imperceptible air particles in such a way as to produce the noises we hear.4
The speed at which sound travels through air determines our perception of its pitch. Shorter, faster-moving sound waves produce high-frequency noises, whereas larger, slower-moving ones make low-frequency, bassy tones.5 That’s why everyone appears to be talking in high-pitched voices when you speed up a song or video clip.
There are a variety of factors that affect the speed of sound, including6:
- The temperature
- The density of the air around it
- The mediums and obstacles it must travel through
Sound Interaction with Room Surfaces
How sound interacts with different surfaces in a room depends on a variety of factors, including:
- Its frequency
- Its amplitude (or volume)
- The hardness and density of the materials it encounters
Regardless of a sound’s pitch and volume or the material it runs into, noise can interact with any given medium in four different ways:
- Reflection – The sound bounces back toward the source—generally off a hard surface such as floors and walls. In the right-sized enclosed space, a singular sound can be reflected multiple times across different surfaces, resulting in an echo.
- Absorption – Generally, dense, thick, and porous materials absorb sound rather than reflecting it back toward its source. That’s why it’s essential to line walls with sound-absorbing materials if you want to keep echoes to a minimum.
- Diffusion – Diffusion is the process of spreading sound out evenly over a space to reduce its energy and amplitude. Diffusors help break up waves and redirect sound to prevent it from building up and becoming overwhelming.
- Transmission – Transmission is what you don’t want. That’s when a sound vibrates its way through walls, ceilings, and floors to make it through into other rooms. This generally occurs when a surface isn’t dense enough to block, reflect, or absorb sound.
Room Acoustics and Sound Behavior
A small, empty room will amplify sound more than a large space filled with furniture and other dense objects. On the other hand, a larger space provides more room for sound to travel between walls, potentially leading to more echoes.
Echoes and reverberation occur when sound travels large distances between reflections. That’s why your voice echoes and carries across empty canyons and wide open mountain ranges, but might not get as far in a forest.
The same logic can be applied to rooms. The greater the distance they travel before sound reflection and the more obstacles they encounter along the way, the less energy they’ll have and, thus, the lower their chances of echo and reverb. Irregular room shapes can also affect sounds, as more surfaces to bounce off means increased potential for sound reflection but, likewise, more obstacles to help zap a sound wave’s energy.
Practical Applications and Soundproofing Tips
So, how can all this scientific understanding actually help you improve your room’s audio quality and prevent sound transmission to other spaces? Well, there are a variety of materials available that can enhance room acoustics or render a space totally soundproof. The soundproofing solutions you’ll need to use depends on the type of space you’re working with:
- Recording studios – Recording studios should be totally noise isolated—meaning you’ll want to install sound isolation clips to decouple the room from the rest of your building and mitigate vibrational noise transfer. You’ll also want to completely cover your walls with sound-absorbing materials such as acoustic panels to minimize the potential for echo. Finally, since the gaps around doors are prime places for noise to escape through, you’ll want to install a heavy, soundproof door to keep sound shuttered inside.
- Home theaters – Home theaters need to uphold solid acoustics but also need to be dark and cozy to enhance your viewing experience. To strike the perfect balance between light and sound absorption, install Fabrisorb Fabric Wrapped Sound Absorbing Wall Panels in a dark color of your choosing.
- Other spaces – From bedrooms to kitchens and everything in between, nearly any space can be soundproofed or have its acoustics enhanced. To prevent noise transfer between adjacent spaces, use sound isolation clips to decouple rooms, line the walls with heavy, dense acoustic panels, and close up any cracks and crevices with acoustic sealant to prevent noise leakage.
Advanced Considerations
As previously mentioned, temperature and air density play a part in how far and fast sound can travel. Sound travels faster through hotter, denser air such as that found in tropical environments.6
Architecture also plays a major role in the acoustics of a space—that’s why concert halls are specifically designed to host musical performances. There are only a few basic shapes that expertly-built auditoriums use, but recent research has found that standard shoebox-shaped (rectangular) spaces produce the greatest dynamic range of any style.7
Enhance Your Space’s Sound Quality with Materials from Acoustical Surfaces
Sound is a form of energy that travels through mediums (such as air or walls) in waves. Dense, porous materials tend to absorb sound, while hard, solid surfaces usually reflect it.
There are a variety of materials you can use to manipulate and enhance the sound within your home, office, business, or other spaces to enhance their acoustics and isolate them from other areas.
Acoustical Surfaces carries everything you need to soundproof your space and achieve its highest possible audio quality. We encourage you to use this and other blogs to learn more about the nature of noise and put your knowledge to the test by optimizing your space’s acoustics—and if you have any questions along the way, you can always contact us for sound support.
Sources:
- University of Toronto. What is Sound?. https://www.cs.toronto.edu/
- National Institute on Deafness and Other Communication Disorders. How Do We Hear?. https://www.nidcd.nih.gov/
- British Broadcasting Corporation. Wave characteristics. https://www.bbc.co.uk/
- Princeton University. How Sound Propagates. https://assets.press.princeton.edu/
- National Aeronautics and Space Administration. Doppler Effect. https://www.grc.nasa.gov/
- Iowa State University. The Speed of Sound in Other Materials. https://www.nde-ed.org/
- Science Daily. Greater music dynamics in shoebox-shaped concert halls. https://www.sciencedaily.com/
