What Are Standing Waves In Rooms? - www.AcousticFields.com

- - Today we’re going to talk about what standing waves in rooms are all about. We get a lot of people asking us about them and the easiest answer is that a standing wave is a pressure area and is the result of low frequency energy not fitting in your room.

So in today's video you'll learn:

1. Why pressure areas are usually along our boundary surfaces but can also be throughout the room and what that means to what you hear,

2. Why you should really think of them as the drunk, angry, loud guy in the bar who needs to take a chill pill because he's messing with everyone else's musical experience and

3. Why, depending on the dimension and volume of your room, they can be plus 10, plus 15, plus 20 DB which is no good at all.

So enjoy the video and as always please let me know if you have any follow up questions.

Thanks
Dennis

[kimballwhitaker]

I believe this is not correct. A standing wave occurs when a room dimension is the same size as the length of a wave (or a multiple of the length of wave). When this happens the reflections of the wave all coincide so that high pressure areas occur together and the low pressure areas occur together, always strengthening each other. The sum of these waves (what you actually hear) has a much greater amplitude than a wave whose reflections don't coincide and some of the peaks occur with some of the valleys, canceling each other out instead of strengthening each other. This happens anytime a wave reflection follows the same path as the original wave and is in phase with that wave. So, not just parallel walls, but in a diamond shape (e.g., off the front wall, then the ceiling, then the back wall, then the floor, then back to the speaker), as well as more complex paths. The amount of absorption on these surfaces determines how many times the wave follows the same path before it is extinguished, hence how much magnification the wave receives.

[martingalloway]

Thankyou Dennis - this was a really useful video for me - very much a beginner in this area and found the straightforward language easy to absorb - am currently trying to iron-out wrinkles in the sound stage up in my man-cave; and the first thing to do is work out what my problem is (ie: is it the room, position of kit, interaction of speakers with the floor causing resonance, mix of some or all of these things, etc, etc!) and then consider my options to resolve it. So yeah, thanks again, Martin.

[krismichalsky]

That was a really good explanation of standing waves!! I wish other audio people would take note of videos like this and gear his tutorials (if you will) with a more focused sense than always trying to sell stuff to people that they probably don't even need, like those dang expensive power cables.... /smh
Good job brother, I am going to watch your other videos, keep up the great work!!

[vishnumoorthy]

Love how you explains a concept, but I think this explanation is false. Standing wave requires the available dimensions (of the room or chamber) to match the wavelength (or half or multiples) of the wave itself. And that is why standing wave occurs in discrete frequencies. So it wouldn't be because the wave cannot fit properly in, but because the wave can fit perfectly in it. Keep making more videos tho! the explanation style is so cool!
Cheers,
VAM.

[purpleheart]

I have a question, do Standing waves only affect listening or do they also affect recording? (asking this bc Since I know My room sucks Im better off just managing my vocals on headphones)

[LanceClark]

so, at those points of pressure, the listener would either hear the resonant frequencies as too high or too low, right?

[bentyreman]

great sound on this video dennis, I always love your videos, thankyou

[stefanjong]

Hello good sir.

Im hoping to find understanding about a problem in my basement studio that is part of my newly bought home.

the room is 5.2m by 4.3m and its a square room, its 2.07m high.
there is also a stairs in the corner with a very high ceiling(4.70m). about 1.50m by 1.50m.
theres is also a wooden wall next to the stairs in the (almost)middle of the room wich seems to resonate loudly when i give it a thump with my hand.

Now my problem:
Whenever I play sub (especially A1, 55 hz), something seems to resonate and rings on for at least 1 second in this sub range after the speakers stop producing sound.
Its a very unpleasant experience, as Im into making bass heavy music.

Now i believe it has something to do with the wooden wall next to the stairs, or maybe even the size of the room? maybe even the huge spacious area where the stairs is...


Any help and insights would be very much appreciated.
Stefan

[TempoGroove]

I don't have any bass in my room....It doesn't matter where I place the speakers....no bass.I have a pair of jbl's, I know they can deliver decent bass.where I was living before, everything was ok, the I moved and in this new room they sound like shit although I have the same configuration as in the old

[joe-la-guit]

Can you test these pressure zones with a simple DB meter ?

[mohanan]

sir
Thank you sir, nice explanation. Sir, I have a doubt. Please give me a clarification. It is told that the standing waves are not moving . In that case how the standing wave sound reaches in our ear ?

[MatteoPellegriniSound]

Hi! I have a question. Assume I know exactly where a standing wave node is in my room (at listening position) and I know its Q-factor. I thought i could use a Helmoltz resonator cabinet to get rid of it, but now I think I understand that it's mostly used to reduce the group delay? Would that still do the trick to remove that first reflection that creates the standing wave? I'm trying to find a DIY solution.

[OldSkoolLover]

So when I play a 40 hertz tone in my room that is way too small for this frequency to be heard, does this mean I'm hearing a second or even a third harmonic of the 40hz frequency?

[ginopunsalan]

In your example, a 30hz wave doesn't fit in the room. Does it mean you can't hear 30hz?

[Rene_Christensen]

The problem with modes is exactly opposite of what you are thinking; this whole ‘fitting in the room’ thing. The wavelength at modes actually fits perfectly in the room, that is the key to the self sustainability which can lead to resonances, depending on speaker placement and ear placement. At very long wavelength the room is evenly pressurized and so again that should be viewed as a good thing, and again opposite of your reasoning.

[erikvanandel]

Hello Acoustic Fields,  

Thinking, as a rule of thumb, the frequencies with wavelength's, longer then twice the longest axial distance, between a parallel set of room's boundaries, cannot create standing waves.

Lets name these frequencies: 'sub standing wave spectrum'.

Take the example used in your video. 
A 30Hz wave, in a room with a maximum distance of 18'.
In order to excite the first room mode, the frequency would have to be, approximately 31Hz.

If this room were to have rigid boundaries, and no gap's/ significant 'open window' surface.
Frequencies, having wavelengths, longer then 18', I thought to create 'bulk pressurization' of such a room.

Meaning, no standing waves, but fluctuations of pressure, throughout that room, with the corresponding frequency.

25Hz, being perceived as 25 Hz, not as energy, partially exiting that 18', 31Hz, axial room mode.

Therefore, throughout that room, below 30Hz, no pressure nodes either.

The decay of this 'sub standing wave spectrum', in such a theoretical, sealed, & rigid boundary, small room, probably leaves room for improvement.

Not having such a theoretical room to test this.

If so, where does this reasoning go wrong?

After measuring a small room, for the 'sweat spot', I usually try to get the modal frequency range, correct, by using di-pole woofers.

If the measurements, below this spectrum, show enough transmission loss, or absorption, for the client wanting to go low, boundary woofers for the 'sub standing wave spectrum', deliver (rather sloppy usually, or a source of noise pollution) enough 'umphh'.

Apart from the results, if I'm theoretically incorrect, please, do correct me.

Thank you for your time,

Erik van Andel
Audio Clone

PS Are there Acousic Fields absorbers to be expected, taking care of the sub region? 

[thegrimyeaper]

I was waiting for him to tell us how to fix it. Oh well...

[amirkessner]

I think the explanations are all wrong. Even the first thing said, that standing waves are not standing, is wrong -- standing waves do not propagate as usual waves do. The nodes remain fixed and the amplitude goes up and down at the same place. He said that standing waves are related to wavelengths not fitting in the room, which is the opposite of the truth. He gave an example of wavelengths unrelated to the room dimensions, and talked about excess energy and reflections, and that's how you get standing waves. This is all wrong and irrelevant to standing waves. The example of the loud guy at the bar is also irrelevant. He described standing waves as a pressure area in the room that is louder than the average, including pressure along boundary surfaces, but standing waves have both louder and softer areas, including nulls(!), and room boundaries are not special areas for standing waves and shouldn't have been mentioned.

He failed to mention that standing waves are resonances with wavelengths that are subdivisions of the room dimensions.

[runner]

The explanation seems basically wrong, sorry