What is reverb? The short answer: It’s the persistence of sound in a space after the original sound source has stopped.
It can mean the difference between a dry, professional recording and a hollow, incomprehensible interview. The difference between a clean mix and a muddled mess that doesn’t sound its best outside of the studio in which you mixed it.
Luckily, there are several tips and tricks to tame that recording environment and get a great sounding take whenever you press record. We’re going to run through them in this handy guide, and by the end of it, you’ll be armed with the knowledge to make unwanted echoes a thing of the past.
Our guide on “what is reverb and how to fix it” was originally written in 2018. We update this post periodically to reflect changes in technology, our recommendations, and because we’re always learning new things. We sometimes use affiliate links to products we think you’ll find interesting. We’d earn a small commission, should you choose to buy through them, and never at any extra cost to yourself!
What is Reverb? Reflections, Flutters and Standing Waves
Reverb in a room is a result of reflections.
Sound travels from the source. The sound hits a wall or other surface and bounces back into your ears at a delay, causing a reverb or echo.
But unlike light, sound doesn’t travel along a single path. It resonates outward and bounces against many surfaces simultaneously or in succession, forming several reflections that define your acoustic space.
Additionally, the location and size of something reflecting your audio can cause a build-up of certain frequencies.
Walk into any standard rectangular room without carpeting. Stand near a corner and clap your hands. Unless that room has been built to precise acoustic dimensions, chances are you’ll hear a slight warbling ring after you clap your hands. This ring is called flutter.
Now imagine your voice or your mix in this space, and you’ll begin to understand how that annoying little ring can produce sub-optimal results when recording or mixing there.
Similarly, stand in the corner of the room and speak in a low natural voice. You’ll notice that your lower register resonates more. A boxy reflection occurs as your voice bounces not only off the corner walls and into your ears, but off the ceiling above and the floor below you. This produces a standing wave that unnaturally enhances the bass reflections in your room.
Alright, so How Do I Fix Reverb? (Absorbers & Diffusers)
Fortunately for us, there are several ways to tame a room. And not all of them involve shelling out hundreds of dollars for Auralex products.
Most of these reverb-taming techniques involve things called absorbers and diffusers. But what do we mean by “absorbing” or “diffusing”?
Well, any given surface in a room does one of three things to any sound that hits it: absorb, reflect, or diffuse.
In reality, all surfaces do all of these things to one degree or another, depending on the characteristics of the sound, but it helps to understand it more simply.
The characteristic we’re most trying to avoid in our space is reflection. Specifically, direct reflections that are going to bounce off the walls and into your ears or microphone.
This means that we want to create a space that either absorbs or diffuses the sound in the room – without necessarily deadening the sound of the space being recorded in.
So, what exactly can we add to our recording setups or environments to help absorb or diffuse the sounds around us? Here are a few options.
A gobo (an industry name, short for “go between”) is mounted to a microphone stand to absorb sound behind the microphones and to the sides. They’re also referred to as reflection shields.
Reflection shields work great in non-harsh acoustical environments that just need a little absorption to prevent echo. If you are recording in a bedroom or a clothes closet, this may be all you need.
Acoustic or Sound Blankets
Sound blankets (AKA, Moving blankets) are a staple for controlling sound in film and audio recording locations. Be sure to get the quilted moving blankets, as they absorb sound much better.
I used some inexpensive shower rings to hold the sound blankets to the PVC and get solid professional results.
Looking around the internet, you might get the impression that Auralex has cornered the market on sound absorption materials. Thankfully (and less expensively) nothing can be further from the truth.
For a bit of the DIY treatment, some Owens-Corning 703 fiberboard wrapped in burlap, duckcloth or similar, has great absorption.
Here are some options for buying studio foam absorbers, too.
Types of Absorbers for Reverb
One type is porous absorbers, which are made of materials like fiberglass or mineral wool. They work by absorbing sound energy as it passes through small pores in the material. Porous absorbers are great for absorbing high-frequency sounds, but not as effective for low-frequency sounds.
Another type is membrane absorbers, which consist of a flexible membrane stretched over an air gap. When sound waves hit the membrane, it vibrates and converts the sound energy into heat. Membrane absorbers are effective at absorbing mid-range frequencies.
Panel absorbers, on the other hand, are made of rigid materials like wood or gypsum board with an air gap behind them. They work by trapping sound waves in the air gap and converting the sound energy into heat. Panel absorbers are effective at absorbing low to mid-range frequencies.
Resonant absorbers are another type of absorber that use a resonant cavity to absorb sound energy. They are made of a box with a hole in it, filled with a material like fiberglass. When sound waves enter the box, they bounce around and lose energy, which is then absorbed by the fiberglass. Resonant absorbers are effective at absorbing low-frequency sounds.
Finally, diaphragmatic absorbers are similar to membrane absorbers but use a stiffer, heavier material like plywood. When sound waves hit the diaphragm, it vibrates and converts the sound energy into heat. Diaphragmatic absorbers are effective at absorbing low-frequency sounds and are often used in recording studios.
Where to Hang Your Absorbers & Diffusers
Okay. So, you’ve got your absorbers and/or diffusers and you want to know where to put them. Here are two methods to get you going.
Method 1: There’s An App For That
Auralex has produced an app for both Android and iPhone that helps you map your recording space and shows you the optimal placement of absorbers and diffusers in your space. The original web-based version is also available here.
Method 2: The Mirror Test
The mirror test is a fairly simple means to determine where to hang your acoustic foam.
- Place your monitors (for a listening room) or a stationary object (for a vocal room) where the monitors or speaker will normally stand.
- Place a compact or hand mirror against each wall in the room, level with the monitors or object.
- Mark any spots along the wall where the monitors or object are visible from the mirror while standing directly in front of it, including the wall directly in front of and behind, as well as the ceiling.
- Install your foam and diffusers where you’ve marked using the mirror.
What is Reverb & How to Fix It: FAQ
Should Podcast Home Studios Be Entirely Free From Reverb?
In short, no. Reverb will almost always be there, even when you’ve treated your room enough that you can no longer hear it.
Many podcasters won’t be in a position to entirely treat an environment, either. Getting rid of excessive reverb or echo is important if you want your content to sound semi-professional, but if “good enough” means you can now get on with your content creation, then leave it at that.
Of course, if you’re really struggling on this front, you always have the option to take your recording outdoors. Check out our full guide to help weigh up whether this is a good option for you.
What Kind of Walls Are Worst for Reverb?
Generally speaking, hard and smooth surfaces are the ones you want to avoid.
Think of a recording studio with walls made of concrete, glass, or metal. These walls don’t absorb sound very well, instead, they reflect it back into the room. This creates a lot of reverb or echo, making your audio sound muddy and indistinct.
On the other hand, soft and porous walls are much better for reducing reverb. Walls made of materials like foam, fabric, or cork absorb sound waves, preventing them from bouncing around the room.
What is Reverberation Time, Reverb Times, or Reverb Decay?
As we’ve covered already, reverb is created when sound waves bounce off surfaces in a room, creating a series of reflections. The time it takes for these reflections to decay and dissipate is known as the reverberation time or reverb time.
In other words, the reverberation time is the length of time it takes for sound to decay by 60 decibels after the sound source has stopped. This time is typically measured in seconds and can vary depending on the size and shape of the room, as well as the materials used in the construction of the walls, ceiling, and floor.
Reverb times are important to consider when recording audio because they can greatly affect the quality and clarity of your recordings. Rooms with long reverb times can create a lot of echo and make your audio sound muddy, while rooms with short reverb times can create a dry, sterile sound.
What Are Reverb Tails?
Similar to the terms above, reverb tails are the lingering echoes that continue after the original sound has stopped. They’re an important part of the overall sound of a recording, and can greatly affect its perceived quality and depth.
Short reverb tails can create a more dry and upfront sound, while longer reverb tails can add depth and space to a recording. The character of the reverb tail can also vary depending on the type of reverb effect used – for example, a plate reverb may have a smoother, more natural decay, while a digital reverb may have a more precise and defined decay.
Conclusion: What Is Reverb? (and How Do I Fix It?)
Really effective sound treatment doesn’t have to cost an arm and a leg. A little DIY and some diligent mirror work can save you a bundle on equipment and immeasurably improve the sound of your recording or mixing space. Your podcast listeners will notice the difference!
If you’d like more tailored help with creating your recording environment and improving your audio quality, check out Podcraft Academy – that’s where you’ll get access to all of our courses, and we run weekly live Q&A sessions in there, too!