When sound hits a solid surface, several different outcomes happen.
Part of the sound waves reflects into the room to preserve the energy. Some of it gets transmitted through the surfaces to escape the area.
After it makes this escape, it’s no longer part of the sound field and gets ignored.
When some of the sound waves get absorbed by a solid surface, the energy gets lost.
If you think about reflective surfaces, a mirror comes to mind first. Light bounces back from the silvered coating at the back of the glass to create a specular reflection.
Can the same thing happen when sound encounters a mirror?
Bouncing Sound off a Mirror?
Sound travels as waves in the same manner as light. The only difference is that the audio signal doesn’t travel as quickly. When those waves encounter a surface, whether it is a solid, liquid, or gas, it must follow the laws of reflection and refraction. It reflects from any surface, including mirrors.
Sound waves reflect from solid surfaces. The way that it impacts the surface will create the eventual reflection you encounter.
It’s a simple equation. The angle of incidence (AOI) matches the angle of reflection (AOR). It can also be expressed as AOI = AOR.
That means a sound wave from an electric guitar amp that hits a mirror at 47 degrees will get reflected at the same angle.
If you have a light box, angle measurer, and a mirror, you can test this equation yourself at home.
The difference between sound and light waves when they strike a mirror is based on the unique qualities of each one.
When you bounce light off of a mirror, the waves get reflected uniformly to you so that an image gets produced.
What you see in the reflection are light waves headed back to you after an initial bouncing act.
If you bounce a sound wave off of a smooth surface, it produces strong echoes. That’s because you don’t get the uniform rate coming back in your direction due to the slower traveling speed.
That’s why you need to think about the AOI = AOR principle when playing music in a space with solid surfaces.
If the sound waves impact at 90 degrees, you’ll get a severe echo that could interfere with your playing style.
Comparing Sound and Light Waves
Since sound and light both travel as waves, it makes sense to compare them.
It’s easy to think of them as “identical properties,” but there are two crucial differences that must be considered when developing your unique style.
| Sound Waves | Light Waves | |
| What wave type is it? | Longitudinal | Transverse |
| Can the waves travel through a vacuum? | No. Sound waves are only capable of passing through solids, liquids, or gases. | Yes |
| Can the waves be reflected? | Yes | Yes |
| Can the waves be refracted? | Yes | Yes |
| Can the waves be diffracted? | Yes | Yes |
| Can the waves create interference? | Yes | Yes |
What is diffraction? It is how the sound or light waves spread out when passing through a gap between surfaces.
The extent to which this happens depends on the wavelength involved and the space’s size.
That means you can create a different sound profile by having two mirrors placed together or having them slightly apart from each other.
You can also focus sound waves to a point, much like you can turn sunlight into a concentrated beam using a concave telescoping mirror.
That attribute creates another audio change that can happen to your music.
If you have a curved mirror available, it will act differently than if the sound bounces off of a flat surface.
What Musicians Need to Know about Refraction
When sound waves (and light waves) pass across the boundaries of two substances with different densities, they change speeds.
Even the barrier between air and glass is enough to cause the waves to change direction.
That process is what we call refraction.
Think back to the famous scene in the original Jurassic Park movie.
When the T-Rex starts coming toward the vehicle, the glass of water starts showing ripples that appear in the center and radiate outward.
From a filmography stance, the idea is to simulate what it would be like to have a massive dinosaur stomping his way toward a potential meal.
When you think about creating those ripples from a scientific viewpoint, refraction’s role takes center stage.
That scene became possible because of a guitar string that connected to the water glass. When someone plucked it, you’d get the water ripples.
Once you start thinking about refraction, you also need to take the AOI calculation into account.
If the sound waves cross a boundary at a 90-degree angle, they’ll continue carrying straight on as if there wasn’t anything in the way.
The traveling speed slows when those waves pass through the barrier, but they return to their typical values after returning to the air.
If the sound waves hit the barrier at an angle, you’ll get reflecting, slowing, and splitting.
When this issue occurs as a speaker plays music from the stage, some listeners will get the high frequencies, others have the mid-range, and more could have the bass.
That’s why you need to consider how the sound echoes when playing in a room.
You’ll also need to consider the various barriers that could change audio speeds, especially when you’re working in a studio environment.
What Is the Refractive Index?
The speed of sound (or light) gets determined by the material through which it is traveling.
Once it leaves one medium and encounters another, the rates can change. That’s how refraction occurs.
The basic calculation for refraction is this: n = sin i over sin r.
In this calculation, “n” equals the refractive index of the materials in question. The “i” is the angle of incidence for the waves, while “r” is the refraction angle.
When you measure the refractive index, it has no units to consider. That means you’re basing the measurement from the way the waves travel through the air.
As a general rule, sound waves travel 1.3 times faster in the air than they do through water.
If you have them hitting glass, a 90-degree impact is 1.5 times as fast in the environment than in that situation.
Why is the refractive index essential to consider from a sound management perspective?
When you have sound waves encounter a mirror, you have three issues to consider.
- The glass for the mirror has a specific thickness that impacts the speed of the sound waves when interacting with each other.
- Mirrors use a backing material that isn’t typically porous, which means the reflected waves must travel back through the glass before they can have their values restored.
- The delay that happens when using this technique can create reverb, vibrato, and other echoing effects, especially when they get recorded in a small room.
After you’ve applied all of these different rules and scientific principles into one equation, you’ll know how a room’s “acoustical profile” will impact your overall playing style.
How to Improve a Room’s Natural Acoustics
You can spend tons of cash on your recording gear and never get an authentic sound from your equipment.
When your studio’s acoustics doesn’t support your playing, the final mix won’t match the expectations you have for the experience.
The first step of this process is to choose your recording room wisely.
There shouldn’t be any reflective walls within the area, and it helps to have lots of things that can scatter the sounds.
Your space shouldn’t be square because the goal is to stop reflections from building up.
Acoustic panels are one of the best ways to turn a smaller room into a recording area. You’ll notice immediate noise reduction in an area of 100 square feet or less with eight-foot ceilings when you use the Mondrian Kit Acoustic Panels.
Once you have the room’s walls ready for sound, you’ll want to deaden other items within that space.
Absorbent materials, such as a sofa along the back wall, can absorb a remarkable amount of sound waves.
Don’t use egg cartons for this step. Acoustic diffusers will always work better!
Here are some additional ways to improve your room’s natural acoustics to have an outstanding recording studio to use.
1. Check Your Monitor Position.
Your monitors should be flush into your wall to avoid sound reflections. If you have a small space, this step isn’t feasible.
That’s when you’ll want to have them about 70cm away from the solid surface.
Each product comes with specific instructions from the manufacturer to maximize its placement within your studio.
Don’t forget to look for items that reduce vibration, such as having rubber feet on the monitor.
The JBL Professional 305P studio monitor provides a sleek design, boundary EQ settings, and updated transducers to ensure you get an impressive frequency sample with lovely lower harmonic distortion.
2. Check for Sound Wave Problems in Your Recording Area.
Most DAW and recording studio software solutions require you to capture the room’s audio measurements.
This step enables your equipment to understand the natural acoustics of the space for automatic EQ adjustments.
You’ll want the flattest response possible, which means any notches require immediate compensation.
You can adjust the basics in your recording area, such as foam panel rearrangement, to take care of those problematic EQ notches.
If you cannot locate the place where offending frequencies refuse to stay flat, you can select a compression microphone to take care of that work for you. The Apogee Hype USB Microphone provides a unidirectional polar pattern that delivers an excellent sound without reflected acoustics. It’s perfect for instruments, podcasting, and more.
Don’t forget about testing for waterfall and reverb times to ensure you get the frequencies you want in your recording.
3. Diffuse the Problematic Frequencies.
A diffusion wall lets you scatter unwanted frequencies from your playing experience.
It’s placed at the points where some waves would get reflected to you, allowing them to refract elsewhere or get absorbed into the materials.
When you have well-placed diffusers in your recording area, you’ll have a better monitoring experience.
It won’t make the room sound dead, but it also eliminates the problems you’ll encounter when too many reflections happen.
Although you could build a diffuser wall in your recording area, the easiest way to reduce problematic frequencies is to use a sound-absorbing shield for your microphone. When you use a product like the LyxPro VRI-20, you’ll have the recording panel on the opposite side of the mic setup, eliminating noise interferences and audience chatter.
4. Use Headphones to Take the Room Out of the Equation.
Although it seems like a cop-out, you can take the studio or recording room out of the equation by using headphones to reference your mixes.
It’s a straightforward way to monitor, especially if external noise is one of your biggest problems.
When you look for headphones to use with your recording efforts, you’ll want to find a model that delivers a flat response.
Although calibration plug-ins can work with your DAW or computer software to improve the EQ you receive, it’s better to buy a product that comes naturally balanced.
When you need everything for your home studio, the RODECaster Pro Production Studio with Audio-Technica ATH-M20x headphones is an excellent deal. You’ll get everything you need to get started with your recording, from music to podcasts, while having ways to improve your mix naturally before the audio enters the DAW.
Should I Be Bouncing Sound Waves from a Mirror?
Although you can bounce sound waves from a mirror to create unique effects, that outcome works better for live performances.
If you can reflect the audio toward the audience, you’ll give them a more profound listening experience when the acoustics are correct.
When you want to record in a home studio, you’ll need to remove as many reflective points as possible from the equation.
That means you’ll need to avoid mirrors, smooth walls, and similar surfaces as much as possible.
It takes a little work to get your home studio set up for recording, but it is an investment worth making.
Once you can create the right acoustics, you’ll find that your music is much easier to mix and edit.