How does a speaker make more than one sound at a time ?

[essexbasscat]

I'm asking as I really don't know, although I suspect the answer will probably be brain warping.

How does a speaker make more than one sound at a time ?

I understand that a speaker cone going in and out so many times per second will produce a sound wave of a corresponding frequency, thereby producing an audible sound. But how does the one speaker produce multiple sounds simultaneously ?

I get images of a speaker going in / out / shake it all about like a jelly on recreational medication, trying to do too many things at once

Anyone have any idea ?

Cheers

T

[ras52]

It doesn't, it just sounds like it does.

If it was just handling a pure sine wave, it would be going in and out in a nice smooth pattern. Otherwise it's handling a complex wave form which is the result of combining the various elements in the sound, and your brain incredibly cleverly decodes this into the sounds of individual instruments, etc.

In fact the speaker is just emulating what happens naturally in the air in an acoustic scenario!

[Mr. Foxen]

Its all one sound. The wave isn't a neat sine, its loads of frequencies combined to a wibbly wave, you only get a series of perfect sine waves if you run a Fourier transform to divide them up. The cunning bit is just after your ears where you divide them up into different sounds, like a guitar and a voice at once, or not cunning when you consider it has been totally conned and isn't a guitar and a voice at all but a vibrating speaker.

[essexbasscat]

They sound like very good, very plausable explanations, which are no doubt informed by previous experience of considering the same question. Thanks for the replies.

But I still don't understand something.

When simultaneous, multiple sounds are occuring at the same time from different sources, how does the speaker recreate that ? i.e. an orchestra, or a band, or any other kind of ensemble, where [i]n [/i]number of instruments are simultaneously producing different sounds, each with their own characteristics.
If the speaker tries to reproduce the sound at time point [i]x, d[/i]oes the speaker sum total the frequencies ? logically no, because that in itself would produce a sound different from the sources.

Or, does the speaker give a microsecond to reproducing each sound, thereby producing Mr. Foxen's wibbly wobbly wave ? i.e. a microsecond at one number of excursions of the cone and a further microsecond for another number of excursions.

I guess to clarify my question, how does the one speaker mechanically produce [i]n [/i]different sounds ?

Thanks again for the replies

[ras52]

Think of the orchestra example: without any amplification, what hits your ear is the complex (wibbly wobbly) wave that arises in the air from the natural confluence of also-complex (wibbly wobbly) waves of the individual sound sources (instruments, ambient noise...). All this happens naturally.

In a reproduction system with perfect fidelity, the speaker would reproduce that very same complex wave: it's told to do so by an incoming electrical signal whose oscillations are analogous the wave in the air.

[brensabre79]

To clarify the answers you've had. It is one sound made from a combination of sounds.

Just like if you mix red paint and green paint in one tin you get a tin of brown paint.

[xgsjx]

Have you got a DAW on your computer (such as Reaper, Garageband, Cubase, etc)? If so, load an audio file (.wav).

Now when you look at it, it's jiggedy up & down & all over the shop (whether that be a single instrument or Metallica with a 40 piece orchestra).
This is what is converted to audio & pushed out by the speaker. You don't look at the file & see loads of instruments, you see something like this...



& that's what the speaker sees as well.

[Bill Fitzmaurice]

[quote name='essexbasscat' timestamp='1334852509' post='1622411']
I guess to clarify my question, how does the one speaker mechanically produce [i]n [/i]different sounds ?
[/quote]It doesn't. The waveforms of all of the various sources combine into one waveform.

[KingBollock]

If you take an acoustic Guitar and play the right notes at once you get a chord, which you recognize as one sound, which is made up from the different vibrations of the different strings. A speaker just takes all of the sounds fed into it, as electric pulses, and creates that one sound, or chord, in a very small instance of time.

[fatback]

If you didn't know there were different instruments in the sound, you'd hear an orchestra as one instrument.

[ras52]

[quote name='fatback' timestamp='1334853974' post='1622444']
If you didn't know there were different instruments in the sound, you'd hear an orchestra as one instrument.
[/quote]
Indeed, and this ties in with another thread which discussed people who couldn't/didn't separate individual instruments in a band. Hence the term "ear-training" for the process by which we learn to unscramble what we hear.

[Mr. Foxen]

[quote name='brensabre79' timestamp='1334853386' post='1622425']
Just like if you mix red paint and green paint in one tin you get a tin of brown paint.
[/quote]

With the addition of you look at it, and your brain goes 'Hey, tartan paint'. The errors introduced by various things it what makes some sounds a bit annoying.

[leftybassman392]

Most of it's been said already. The bit that seems to be confusing you turns out to be going on inside your head. The single, er, wibbly wobbly wave that hits your ears (think of them as highly sensitive and incredibly complex pickups) gets turned back into a bunch of different instruments by your brain (which is very VERY good at decyphering the components of the, er, wibbly wobbly wave and deciding what combination of original sounds caused the, er, wibbly wobbly wave in the first place).

As well as this, it's very good at deciding where the different sounds are coming from (so, for example, if you're having a chat with a bunch of people it's possible to close your eyes and still be able to point to each person very accurately).

And here's the best bit, it's all completely automatic so you don't even need to think about it!

Generally speaking musicians are better at it than ordinary mortals because we spend more of our time doing it, but anybody can do it.

[xgsjx]

[quote name='leftybassman392' timestamp='1334873951' post='1622883']
so, for example, if you're having a chat with a bunch of people it's possible to close your eyes and still be able to point to each person very accurately.
[/quote]

Unless like me, you're deaf & don't know when anyone is talking until they hit you!

[1970]

BUT HOW DOES TV WORK?

[leftybassman392]

[quote name='1970' timestamp='1334877528' post='1622983']
BUT HOW DOES TV WORK?
[/quote]

It's all Yogi Bear's fault.

[mart]

Ok, here's a simple example of combining sounds. Suppose you have two flutes, one playing the note A, and one playing the E above it (a perfect fifth). The first flute makes a soundwave like this:

As time passes (from left to right), the air is alternately pushed (as the line goes up, like happens around the number 2 and around the number 8), and pulled (as the line goes down, between 4 and 6, and between 10 and 12), and then it just repeats.

Meanwhile, the second flute is making a soundwave like this:

So it's also alternately pushing and pulling the air but at slightly different times. Around time 2, the first flute is pushing, but the second isn't really doing anything much. Around time 9 both are pushing the air. So sometimes they're doing different things, sometimes the same thing, and sometimes completely opposite things (e.g. around time 5).

Your ear just feels the combined effect, which is just the sum (as you said, although not the sum of "frequencies" but the sum of these pushes and pulls). When one is pushing and the other pulling, they obviously cancel, but when both are pushing (or both pulling) they combine. So your ears feel this:


Similarly, if you want your leadspeaker to pretend to be two flutes, then you get it to move so as to push/pull the air like this. The miracle that leftybassman referred to is that from this "sum" wave, you can actually work out exactly what the constituents were. It's a bit of a miracle that it can be done even theoretically (using the magic of Fourier analysis) and a whole other miracle that our brains can do it without us even noticing (or having to do any calculus).

And what's even more amazing is that there's nothing special about just having two notes. You can have a whole bunch of notes played together and still work out what they were, even if the combined wave looks something like this:

(Which, if I've got the numbers right, should be a major triad).

[flyfisher]

[quote name='essexbasscat' timestamp='1334850248' post='1622359']
How does a speaker make more than one sound at a time ?
[/quote]

In the same way that a bass string makes more than one sound (frequency) at a time - it has multiple modes of vibration.

[ShergoldSnickers]

It always amazes me when you see electron micrographs of LP grooves. The fact that the stylus - for the most part - manages to track the waveforms, but also has to cope with two independent waveforms, one on each groove wall. It's staggering how good this simple mechanical arrangement can sound if the engineering within the cartridge, arm and turntable is right.

[leftybassman392]

A miracle indeed. As a musician with a bit of a scientific bent I suppose I would say this but I happen to think that the human brain's ability to identify and locate multiple individual sound sources from a single, unbelievably complex waveform virtually in real time is one of our more remarkable abilities - and the more remarkable in that it requires little or no conscious intervention from us.

[leftybassman392]

[quote name='ShergoldSnickers' timestamp='1334910145' post='1623216']
It always amazes me when you see electron micrographs of LP grooves. The fact that the stylus - for the most part - manages to track the waveforms, but also has to cope with two independent waveforms, one on each groove wall. It's staggering how good this simple mechanical arrangement can sound if the engineering within the cartridge, arm and turntable is right.
[/quote]

..... and a testament to the genius of the engineers who designed and developed it.

[essexbasscat]

Question. Using entirely hypothetical, random figures here;

If one instrument plays a note of say 240 Hz and a second instrument plays a note of 435 Hz, why does the speaker produce two notes and not the one note associated with the sound of 240 + 435 = 675 Hz ?

[ShergoldSnickers]

[quote name='essexbasscat' timestamp='1334922273' post='1623471']
Question. Using entirely hypothetical, random figures here;

If one instrument plays a note of say 240 Hz and a second instrument plays a note of 435 Hz, why does the speaker produce two notes and not the one note associated with the sound of 240 + 435 = 675 Hz ?
[/quote]

If we take a step back and consider two instruments playing the same frequency, say 435 Hz, it doesn't make sense that the result would be 870 Hz, an octave above. Instead, you get a louder 435 Hz. It could get interesting if this frequency addition did happen though. The possibilities...

[essexbasscat]

That makes good sense Snicks and has the ring of truth to it. yet how to make sense of the previous posts that say all the sounds are combined ? If they're combined, then how ?

edited for spellnig mitsakes

Edited April 20, 2012 by essexbasscat

[ShergoldSnickers]

[quote name='essexbasscat' timestamp='1334923203' post='1623487']
That makes good sense Snicks and has the ring of truth to it. yet how to make sense of the previous posts that say all the sounds are oombined ? If they're combined, then how ?
[/quote]

We need a long skipping rope with someone doing oscillations at one frequency, and someone at the other end doing them at a different frequency. I'll post you your end.