A while ago, I posed a question to the install bay techs at the shop I work for. We tossed it around for a while, but came to no real conclusions. My question was this. If you had a bunch of speakers (100, 1000, 1000000, it doesn't matter how many, nor how big, but a bunch of them) hooked up to different sources (ie, each one is playing a different song) and you played them all simultaneously...what would you hear?
Theory One: A composite tone which is the average of all the frequencies.
Theory Two: Static. White (or pink, I forget which) noise like you get when you are between radio stations.
Theory Three: Nothing (all frequencies are equally represented and cancel each other out through destructive interference)
Just curious what everyone thinks.
Replies (5)
uochronos on 05/21/2004 02:51:33
i think personaly you would end up with static not 100% sure but it seems to me they would not all cancel out or be averaged out... seems they would all disrupt the waves of the others causeing a static type sound.. like i said this is just an opinion on limited knowledge. but no matter the out come not something i would want to hear being an sq nut lol
swez on 05/21/2004 10:19:12
Interesting question and you only need to stick your head outside the back door and listen a few minutes to get your answer... MAYHEM is what you would hear... Traffic noise, birds chirping, rain and thunder, tree leaves rustling in the wind, horn honking, engines reving, lawn movers, dogs barking and so much more.
See, the ear and the brain work together to integrate or focus on external sounds. We can detect many kinds of sound whether coming direct from a sound source like a car engine running or a speaker playing music. It does not matter what the sound source is... we can still detect both quiet and loud sources of sound.
OK, now let's look at acoustics a bit. In a confined space, you still have many sounds happening in a shop environment right? Power tools running, car audio systems being tested, background music and pages over the PA system, a guy cussing his head off as he just got the same car back for the 5th time to debug, someone eating his lunch and belching from the 32 oz pop he just guzzled and so much more. Well, these are all sound sources floating around in the room.
The things you will hear most, are the higher SPL sounds. (A saw cutting wood, an air chisel, air drill, and air compressor filling the air tank etc.) The lesser SPL sounds will be overpowered by high SPL sounds. But we can still detect each sound as we focus on what we wish to hear.
Want to test this in real time? Go to a large store that has say 50 TV sets all playing different channels. It will sound like MAYHEM as you stand at a distance and listen. But as you walk past each TV set, you will hear mostly that TV channel audio, (proximity effects) assuming they are all playing at say 90dB per set.
Try this and see for yourself, how the ear and brain can both integrate (combine) and isolate (focus) on many incoming audio sources. Our senses are amazing tools to use and the brain can select or reject whatever we choose. THINK
Swez
PS One more maddening puzzler... if a tree in a forest falls to the ground, but no body was there to see/listen to it fall... did it make any noise as it toppled to the ground?
Pinch on 05/22/2004 12:14:28
See, at first I was with Uochron on this. I figured that if you had enough speakers playing something different at the same time, eventually ALL audible frequencies would be represented (at some volume) at any one point. My question just became then, what would THAT sound like. Well, Swez your busy shop relation was good. That does sound like mayhem sometimes :). And my Big Backyard (used to love that magazine) does indeed sound for lack of a better word busy. However that isn't fair because each source is such a great distance apart. Traffic, birds, wind, etc are all loud if they're right next to your ear, but not across town. What happens if you take (as a dramatic example) all the noise comming out of, say, Los Angeles and somehow make it come out of my back yard instead. Now, my neighbors would clearly love this, and I am sure there is a City Ordinance against making all of the sound from Los Angeles come out of your back yard, but lets pretend anyway. What would you hear if you were to stand in the middle of the yard? I just can't think of anything I've experienced like that. A basketball stadium is close, but that's just mostly people talking. To be fair, frequencies beyond what most people can belch forth are necessary. Hmm, it's a thinker...
swez on 05/22/2004 12:54:40
This is a good puzzler and yes, I am sure there would be some degree of cancellation in a small room full of speakers. But... since they are all playing different programming at the same time, (assuming a 360 degree radius of sounds) you will still hear integrated sounds but more like noise. If you focused you ears on a specific source, we can usually detect that as well.
Now, if you were in the center of the room and all speakers will playing the same source music at once. I would thing some cancellations would become evident. But to what extent??? Hard to say without an RTA to compare original audio source clips VS group array clips. An interesting experiment on a slow day huh?
Swez
Relax_The_Mind on 05/23/2004 07:47:48
Well actually of those three options you would choose two hear an average tone... but more like a long sine wave of a tone yet with a sort of static. With 100-10000+ speakers playing different sounds and such the constant mixing, paralleling, gains and attenuation it would most likely come to a equilibrium (
You have to think... if you had 100-10000+ speakers... that is a buttload. Similar effect is like being in a really crowded school cafeteria (~300 students or so) its not just people talking but chairs, food, trays, etc. It sounds like a really long sine wave in loop.
SIDE NOTE:
now for cancellation... cancellation comes from an equal and opposite force. In your store (with them all using the same source of course) I would think there would be a couple dead areas and a couple areas that would hurt your ears. Meaning given a correct distance from speaker to speaker you will either hear it really loud or very attenuated. I have helped designed sound studios and booths, pretty fun actually. If you have ever stepped into an actual recording studio its like you stepped into another world. you can hear your heartbeat and the odd "fuzz" of silence. Its just...different. The walls covered in directional sound deadeners to both absord and redirect sound waves mostly for higher frequencies and then bass traps which are basically a box in a wall, floor or ceiling full of insulation.
RTM, Audio Engineer
Theory One: A composite tone which is the average of all the frequencies.
Theory Two: Static. White (or pink, I forget which) noise like you get when you are between radio stations.
Theory Three: Nothing (all frequencies are equally represented and cancel each other out through destructive interference)
Just curious what everyone thinks.
Replies (5)
uochronos on 05/21/2004 02:51:33
i think personaly you would end up with static not 100% sure but it seems to me they would not all cancel out or be averaged out... seems they would all disrupt the waves of the others causeing a static type sound.. like i said this is just an opinion on limited knowledge. but no matter the out come not something i would want to hear being an sq nut lol
swez on 05/21/2004 10:19:12
Interesting question and you only need to stick your head outside the back door and listen a few minutes to get your answer... MAYHEM is what you would hear... Traffic noise, birds chirping, rain and thunder, tree leaves rustling in the wind, horn honking, engines reving, lawn movers, dogs barking and so much more.
See, the ear and the brain work together to integrate or focus on external sounds. We can detect many kinds of sound whether coming direct from a sound source like a car engine running or a speaker playing music. It does not matter what the sound source is... we can still detect both quiet and loud sources of sound.
OK, now let's look at acoustics a bit. In a confined space, you still have many sounds happening in a shop environment right? Power tools running, car audio systems being tested, background music and pages over the PA system, a guy cussing his head off as he just got the same car back for the 5th time to debug, someone eating his lunch and belching from the 32 oz pop he just guzzled and so much more. Well, these are all sound sources floating around in the room.
The things you will hear most, are the higher SPL sounds. (A saw cutting wood, an air chisel, air drill, and air compressor filling the air tank etc.) The lesser SPL sounds will be overpowered by high SPL sounds. But we can still detect each sound as we focus on what we wish to hear.
Want to test this in real time? Go to a large store that has say 50 TV sets all playing different channels. It will sound like MAYHEM as you stand at a distance and listen. But as you walk past each TV set, you will hear mostly that TV channel audio, (proximity effects) assuming they are all playing at say 90dB per set.
Try this and see for yourself, how the ear and brain can both integrate (combine) and isolate (focus) on many incoming audio sources. Our senses are amazing tools to use and the brain can select or reject whatever we choose. THINK
Swez
PS One more maddening puzzler... if a tree in a forest falls to the ground, but no body was there to see/listen to it fall... did it make any noise as it toppled to the ground?
Pinch on 05/22/2004 12:14:28
See, at first I was with Uochron on this. I figured that if you had enough speakers playing something different at the same time, eventually ALL audible frequencies would be represented (at some volume) at any one point. My question just became then, what would THAT sound like. Well, Swez your busy shop relation was good. That does sound like mayhem sometimes :). And my Big Backyard (used to love that magazine) does indeed sound for lack of a better word busy. However that isn't fair because each source is such a great distance apart. Traffic, birds, wind, etc are all loud if they're right next to your ear, but not across town. What happens if you take (as a dramatic example) all the noise comming out of, say, Los Angeles and somehow make it come out of my back yard instead. Now, my neighbors would clearly love this, and I am sure there is a City Ordinance against making all of the sound from Los Angeles come out of your back yard, but lets pretend anyway. What would you hear if you were to stand in the middle of the yard? I just can't think of anything I've experienced like that. A basketball stadium is close, but that's just mostly people talking. To be fair, frequencies beyond what most people can belch forth are necessary. Hmm, it's a thinker...
swez on 05/22/2004 12:54:40
This is a good puzzler and yes, I am sure there would be some degree of cancellation in a small room full of speakers. But... since they are all playing different programming at the same time, (assuming a 360 degree radius of sounds) you will still hear integrated sounds but more like noise. If you focused you ears on a specific source, we can usually detect that as well.
Now, if you were in the center of the room and all speakers will playing the same source music at once. I would thing some cancellations would become evident. But to what extent??? Hard to say without an RTA to compare original audio source clips VS group array clips. An interesting experiment on a slow day huh?
Swez
Relax_The_Mind on 05/23/2004 07:47:48
Well actually of those three options you would choose two hear an average tone... but more like a long sine wave of a tone yet with a sort of static. With 100-10000+ speakers playing different sounds and such the constant mixing, paralleling, gains and attenuation it would most likely come to a equilibrium (
You have to think... if you had 100-10000+ speakers... that is a buttload. Similar effect is like being in a really crowded school cafeteria (~300 students or so) its not just people talking but chairs, food, trays, etc. It sounds like a really long sine wave in loop.
SIDE NOTE:
now for cancellation... cancellation comes from an equal and opposite force. In your store (with them all using the same source of course) I would think there would be a couple dead areas and a couple areas that would hurt your ears. Meaning given a correct distance from speaker to speaker you will either hear it really loud or very attenuated. I have helped designed sound studios and booths, pretty fun actually. If you have ever stepped into an actual recording studio its like you stepped into another world. you can hear your heartbeat and the odd "fuzz" of silence. Its just...different. The walls covered in directional sound deadeners to both absord and redirect sound waves mostly for higher frequencies and then bass traps which are basically a box in a wall, floor or ceiling full of insulation.
RTM, Audio Engineer
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