Home Studio Recording: Let’s Talk About Standing Waves, Nodes and Anti-Nodes (and How to Avoid Them)

If you are looking for a great sound in your home studio, there’s one main thing you have to consider: acoustics. Yes, that’s right. In fact even the coolest gear will be (almost) useless if you use it in a crappy sounding room. So, as long as you are not just mixing through your headphones (hopefully not!) you may find this post interesting.

I know that acoustic treatment is a complicated  and long topic. We could talk about it for days and still not come to the right solution for your studio. Simply because every studio is (and sounds) different. Nevertheless, the following article may be of some help when you have to make important decisions about your mixing position and acoustic treatment.

Introducing… Standing Waves

Today, I’m going to tackle a specific topic: standing waves, and therefore nodes and antinodes. You’ve probably already heard that standing waves affect the sound in your studio and you should avoid placing monitors where standing waves are more likely to occur. That is correct, but, how do we know were a standing is and why nodes and antinodes are so bad for our ears?

First of all, let’s read a clear definition of standing wave, node and antinode. Here it is:

Standing waves result when two sinusoidal wave trains of the same frequency are moving in opposite directions in the same space and interfere with each other.[2] They occur when waves are reflected at a boundary, such as sound waves reflected from a wall. (…)

node is a point along a standing wave where the wave has minimum amplitude. For instance, in a vibrating guitar string, the ends of the string are nodes. By changing the position of the end node through frets, the guitarist changes the effective length of the vibrating string and thereby the note played. The opposite of a node is an anti-node, a point where the amplitude of the standing wave is at maximum. These occur midway between the nodes. (Source: Wikipedia)

450px-Standing_wave
A standing wave. The red dots are the node points (Source Wikipedia)

In other terms, if our listening position is where the node is, that frequency (and its multiples and halves) will be cancelled, or we will hear it with much less amplitude anyway.  Instead, if we position ourselves where an anti-node occurs, that frequency will be strongly amplified, because it sums up with all the same-frequency reflections occurring in the room.

The nodes (and anti-nodes) will affect the quality of the room response because of sound waves reflection. Needless to say that, if we are in a non-reflective room, the amount of standing waves will be reduced to a minimum. Since we are not working with sinusoidal waves in an anechoic chamber, but we deal with complex sounds in a studio, there’s always the chance of having annoying frequency issues going on.

The Lower, The Worse

Sound waves travel through, air causing pressure variations proportionate to their frequency. That’s why we represent them as waves. The wavelength is the physical distance that this pressure variation has to travel before it completes on cycle.  High frequencies have short wavelengtt, while low frequencies may have a wavelength that exceeds the dimensions of your studio.

Some examples:

  • 500 Hz = wavelength is 0,70 meters
  • 1000 Hz = wavelength is 0,34 meters
  • 5000 Hz = wavelength is 0,06 meters
  • 80 Hz = wavelength is 4,30 meters 

To calculate the wavelength we simply divide the speed of sound (343 m @ 20° C through Air) by the frequency (which is a function of cycles per second).

If you want to have fun calculating frequency wavelength, and therefore get an idea – still confused but realistic 🙂 – of your room’s problem areas, here’s a handy online calculator. Keep in mind that you are going to have cancellations even at multiples of the fundamental problem frequency.

corner bass trap Pulse
Pulse – corner Bass Trap by UA Acoustics – available at Amazon.com

What’s the worst place where you would record or mix? Let’s pretend you have a room that measures 3 x 3 x 3, with flat walls and ceiling.  Basically a cube. Here, nodes and antinodes will clearly audible. You don’t need complicated measurements to understand that a frequency with a wavelength of 3 meters (and its harmonics: 2x, 4x,  8x, and so on) will have a strong node in the middle of the room.

The complexity of the reflections will give little help: we have 3 metres for each room dimension and this means that the node (and anti-nodes) will happen all in the same places and (therefore) will be audible. In this exact case, you will have a standing wave at approx 115 Hz (and multiples) and a node in the middle of the room.

How Does Sound Goes Around: The Wavelength Travel

Because of their shorter wavelength and different amount of energy, mid and high frequencies will reflect, but distribute evenly within the room volumes. This means that the room will have a more “live” or “dead” sound, depending on the amount of mids and highs reflections on all surfaces.

The problem lies with low frequencies, as when they bounce from the walls, they will still have enough energy to travel. If the wavelength of these low frequencies matches one or more dimensions of the room, there are going to be frequency cancellation in some areas and reinforcements in other areas. The smaller your room, the more you have to think about putting bass traps to avoid low frequency resonances.

If you have to use a regular room, where the walls are placed at a 90° to each other and the ceiling is flat, consider breaking this evenness putting a heavy curtain on one of the walls and acoustic panels on the walls. If you avoid direct reflections, you are most likely to end up with a nice high end frequency response.

But what about those big sized, lengthier low frequencies? As you know, most of their energy can’t be stopped by pyramidal absorbers glued to the walls. Not only that, but LF will travel around furniture, desks, everything, until they lose their energy. And they will be the cause of bad resonances and a possible node (or anti-node) problem.

When treating the room, then, place bass traps where you hear the LF build up. It’s usually next to the walls and into corners. Always keep in mind that (ideally) without any reflections, we automatically get rid of most of the standing waves (read reflections) related problems.

On the other end, keeping some reflections can also be a good choice, as they add some liveness to the rooms, which be nice to hear. As for everything in life, truth (and nice sound) lies somewhere in between. Before making any permanent or no-way-back decision, listen, compare, and then listen again. It will save you a lot of time when working.

The Listening Position

When setting up your studio, your listening position should (almost never) be in the middle of the room: here is where you’ll get most problems. At the same time, you don’t want to stick to the walls: you’ll be getting anti-nodes there.

Let’s assume that we can’t achieve perfection (especially in you bedroom home studio), but if you know where the problem is, you’ll be halfway to the solution.

Having said that, keep in mind that there’s always a frequency range or two that are going to weirdly resonate, especially at low frequencies with high energy.

Once you’ve found the right position, try to “align it” at equal distance from the side walls. This might sound contradictory with what previously said about the presence of reflections and nodes that color the sound. But to ensure that your listening position is correct, you must to have the same “thing” happening on both sides of your ears.

To make an extreme example, in a large room, if you position one monitor next to a wall and the other closer to the middle of the room,  the reflections/diffractions/reverberation from each side will be of different quality. This could affect you mix.

As most problems usually happen in the middle of the room or next to the walls, choose a mixing (and monitoring) position between the middle and one of the walls, so that you don’t get direct reflections. When you are setting up the studio, listen to a lot of reference material, to help you in making decisions. If the problem can’t be completely fixed,  pay particular attention to the way you use the EQ, as it is your main tool to compensate frequency issues.

Thank you for reading, I hope you’ve found this helpful. You can subscribe to this blog or follow us on Twitter 🙂 . Below, there are some suggestions on acoustic panels that you can find on Amazon.com.

Ultimate Acoustics UA Kit SB3G
Ultimate Acoustics UA Kit SB3G – Available at Amazon.com
Aokeo Professional Recording Microphone Isolation Shield
Aokeo Professional Recording Microphone Isolation Shield – Available at Amazon.com

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