#soundsystem #audioequipment #decibels #speakers #syncedspeakers
Have you ever wondered if having multiple speakers playing in sync at a certain decibel level can create a louder sound than just one speaker? It’s a common question that many people have, and the answer can be a bit surprising. So, let’s dive into the world of sound systems, decibels, and the science behind multiple speakers playing in sync.
Understanding Decibels
Before we dive into the question at hand, let’s take a moment to understand what decibels (DB) are and how they relate to sound. Decibels are a unit of measurement for sound intensity or loudness. The DB scale is logarithmic, meaning that the increase of 10 DB represents a tenfold increase in intensity. For example, 70 DB is 10 times more intense than 60 DB.
Now, let’s get back to the original question. If you have 3 separate speakers, playing in sync, at 40DB each, do you now have sound louder than 40DB because there’s not 1 but 3 speakers?
The Science Behind Multiple Speakers
The short answer is no, having multiple speakers playing at the same decibel level does not necessarily create a louder sound. Here’s why: when multiple speakers are playing the same frequency at the same level, they essentially combine to create a sound that is no louder than the individual speakers. It’s similar to having multiple people speaking at the same volume – it doesn’t make the collective sound louder, just spread out.
However, there are certain scenarios where having multiple speakers can create a perception of louder sound. For example, when speakers are strategically placed to create a surround sound effect, it can give the illusion of a larger, more immersive sound. But in terms of pure decibel level, it remains the same regardless of the number of speakers.
What Happens with Additional Speakers?
So, what happens if you keep adding speakers, still at 40DB playing in sync? Will the sound get louder with each additional speaker? The answer is still no. Adding more speakers at the same decibel level will not increase the overall volume. Each speaker will continue to contribute to the overall sound without actually increasing the loudness.
However, there is a practical advantage to having multiple speakers playing in sync at the same level. When placed strategically, it can help distribute the sound more evenly throughout a space, reducing dead spots and creating a more immersive listening experience.
Conversational Wrap-Up
In conclusion, while it may seem intuitive that having multiple speakers playing in sync at a certain decibel level would create a louder sound, the science behind it tells a different story. Having multiple speakers does not inherently increase the overall volume, but it can enhance the distribution and perception of the sound.
So, the next time you find yourself with multiple speakers playing at the same level, remember that the decibel level remains constant regardless of the number of speakers. With proper placement and synchronization, multiple speakers can still enhance the listening experience, even if they don’t make the sound objectively louder. And hey, understanding the science behind it all adds a whole new level of appreciation for the world of audio equipment! 🎵
Yes, absent interference or varying distances to the additional speakers, the combined sound will be louder than each individual speaker.
But the decibel scale is logarithmic: doubling the amount of sound adds about 3 dB, ten times the amount of sound adds 10 dB. In your case, 2 speakers will be 43 dB, 3 will be around 45, 4 will be 46, 10 will be 50.
No the sound will still be 40 db but the area covered will be larger.
Consider a single frequency output of 40 db. A speaker cone will have to move in and out a specific amount to create this sound. The movement of the speaker cone compresses the air which travels as a wave to your ear. If you have 5 speakers all compressing to the same level, the sound that reaches your ear will be the same as one speaker.
I am ignoring the likely hood of sound bouncing off walls and ceilings, which can create loud spots (even with one speaker).
Consider an air compressor creating an 80 psi pressure. If you connected 5 compressors together you will still get 80 psi but with greater flow capability.
If the two speakers both play a single tone at 40 dB then, neglecting multi-path in the room, you would have points where they combine constructively up to 43 dB and points where the two cancel each other out due to destructive interference.
In a real world environment, the destructive cancellation will not happen due to a variety of effects and it will just generally be louder. (This idea of destructive interference is the same principle that allows noise canceling headphones to work.)
Yea it will be louder IF whatever is playing on them are all being played at the same exact time. So the sound would have to be synced between all of them. If they’re out of sync, it’ll still be loud..but you have the possiblity of some waves cancceling each other out, or causing “disruption” and degrading other sound waves
Lets assume the speaker has no physical body, but just emits sound evenly in all directions from a single point in space.
Put two speakers in the same place and the sound will be exactly twice as loud. Other people in the thread have explained how this works with dB and logarithms, which is unintuitive at first. Perceived loudness, sound pressure levels vs. powers all complicate this further so ignore that and let’s just “yes, it’s twice as loud”.
Put the sound source against a completely reflective wall, and from where you observe the sound, the sound will again be twice as loud as none of it is going in that direction, and is constructively interfering with itself in the direction of the observer. Two speakers, one wall, four times as loud.
So now flip the signal going into one of the speakers (technically inverting the phase – so where on the graph where we once saw a peak now there is a trough and vice versa). The signal will sound the same in isolation, but is opposite to the original. When played together you will now hear exactly nothing, because the sound waves cancel each other out. Instead of adding 1+1 to get 2, we get 1 + (-1) = 0. The sound is gone. This is the basic principle on how noise cancelling headphones work.
The real world is a lot more complicated because the placement of the speaker and all the other troublesome deviations of the real world from the sheer maths of it adds up. Reflections in rooms can cause huge problems for sound engineers both in studios and live situations, because of unpredictable combinations of constructive or destructive interference of sound. Pairs of microphones have to be placed in specific ways such that they aren’t out of phase with each other cancelling out certain parts of the same sound from an instrument.
I assume Op is just using a phone app (or meter) and so the dB reading is base don that.
“dB” is not a uniform measurement but a way of dealing with the fact that the human ear can hear a huge range of sound level energy and can distinguish very small changes at the low end while needing large changes in louder sounds.
The reference (i.e 1 dB) is also not a simple value as there are several scales (dBA, dbB and dBC being common):
https://www.engineeringtoolbox.com/decibel-d_59.html
Also please note that decibel is written with a lower case “d” to denote a 10 base logarithmic scale (“deci”). Seeing “DB” for me is like seeing “PH” or “CM” and it makes me wince.
These usually read “dB-A” or “dB-B”
As long as the speakers’ directionality is similar to the first speaker, then yes for most frequencies it will be louder at the measurement position. The amount of sound energy scales linearly with the number of speakers you place, assuming they are identical.
However sound from multiple speakers will constructively and destructively interfere at different frequencies. This is particularly amplified in rooms with untreated surfaces. At frequencies higher than 100-200 Hz or so, this effect is not particularly noticeable and you will hear sound as being louder.
At low frequencies, especially under 100Hz then you have take into account the room you are listening in and the 3-dimensional position of your speakers. At these frequencies, the wave length of sound is long enough to create standing waves in any reasonable sized room. You can actually predict what these frequencies are with simple “room mode” calculators on the web. If you then play that frequency with a signal generator, you will be able to walk around in your room and hear where the sound has peaks and dips. This is even the case with just a single subwoofer.
If you place multiple subwoofers in spots where these standing waves constructively interfere, then it will make the interference worse and the energy at the wave peaks will scale with the number of speakers. However, if you place the subwoofers in other locations, you can actually counteract some of the standing waves and reduce strength of the peaks, essentially making specific listening locations quieter at these resonant frequencies.
A great program to understand the frequency response of multiple speakers is the room sim in [REW](https://www.roomeqwizard.com). This program is free to download.
A good book for further reading on this subject is “Sound Reproduction” by Floyd Toole
There’s a football stadium a couple of miles from my house. On game day I can hear the crowd cheering and even singing.
If any of those voices were alone at that same distance I’d have no chance of hearing it. Adding more sources applies more vibrational energy to the air.