I would like to start a discussion involving how sound works.


by ymalmsteen887
Tags: discussion, involving, sound, start
JaredJames
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#37
Feb21-11, 06:04 AM
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Quote Quote by ymalmsteen887 View Post
Off topic for a second but is this orchestra playing unamplified?

http://www.youtube.com/watch?v=dYecL...DE08D9FEF14799
I want to say yes (notice the design of the stage - that's not just for looks).

But there are noticeable microphones around, so I'm not perfectly sure. However, I'd say those mics are purely for recording it not for amplification.
ymalmsteen887
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Feb21-11, 08:04 PM
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Quote Quote by jarednjames View Post
I want to say yes (notice the design of the stage - that's not just for looks).

But there are noticeable microphones around, so I'm not perfectly sure. However, I'd say those mics are purely for recording it not for amplification.
I think the microphones are for recording in 2ch audio for later viewing. Why would an orchestra use amplification wouldnt audiophiles complain about that?
JaredJames
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#39
Feb21-11, 08:07 PM
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Quote Quote by ymalmsteen887 View Post
I think the microphones are for recording in 2ch audio for later viewing.
Sounds about right.
Why would an orchestra use amplification wouldnt audiophiles complain about that?
Sometimes the instruments alone just aren't powerful enough to do the job. Although these situations aren't particularly common for your usual orchestra performances.
ymalmsteen887
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#40
Feb21-11, 08:09 PM
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something I dont understand about harmonics. If all musical notes are made up interger frequencies then how come different instruments sound different not to mention the different kinds of flutes gutiars drums etc, can sound different. Same with the human voice like people singing the same vowels yet sound different and even males are distinguisable from females and yet individual males and females can be told apart. How is this explained.
Pythagorean
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Feb21-11, 08:49 PM
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Quote Quote by ymalmsteen887 View Post
something I dont understand about harmonics. If all musical notes are made up interger frequencies then how come different instruments sound different not to mention the different kinds of flutes gutiars drums etc, can sound different. Same with the human voice like people singing the same vowels yet sound different and even males are distinguisable from females and yet individual males and females can be told apart. How is this explained.
The harmonic profile is distorted by reality. That is, real strings aren't massless, don't have perfect tension, there's nonlinear effects (aeolian harp effect, possibly)

So each set of strings is going to have their own specifications based on these "flaws".

Also, there's the sounding technique. If you strum a guitar and wait a couple milliseconds, the higher harmonics die out quickly, leaving a more mellow, pure tone. But with a violin, you're always scratching the string with the bow, so you're not letting the harmonics dies out; you continuously agitate the string, so violins have richer harmonics.

look up "timbre"
ymalmsteen887
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Feb21-11, 10:53 PM
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Quote Quote by Pythagorean View Post
The harmonic profile is distorted by reality. That is, real strings aren't massless, don't have perfect tension, there's nonlinear effects (aeolian harp effect, possibly)

So each set of strings is going to have their own specifications based on these "flaws".

Also, there's the sounding technique. If you strum a guitar and wait a couple milliseconds, the higher harmonics die out quickly, leaving a more mellow, pure tone. But with a violin, you're always scratching the string with the bow, so you're not letting the harmonics dies out; you continuously agitate the string, so violins have richer harmonics.

look up "timbre"
I have looked up timbre. So are you saying that there is more then just the integers. Why doesnt the voilin bowed sound like a guitar being picked continuously. That only tells me why the sound changes on the guitar and not the violin.You said nonlinear effects if you take the fundamental note of a 82hz guitar note and a 82hz cello note that would just be a sine wave so how is it that instruments ,voices sound different?
Pythagorean
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Feb21-11, 11:23 PM
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Quote Quote by ymalmsteen887 View Post
I have looked up timbre. So are you saying that there is more then just the integers. Why doesnt the voilin bowed sound like a guitar being picked continuously. That only tells me why the sound changes on the guitar and not the violin.You said nonlinear effects if you take the fundamental note of a 82hz guitar note and a 82hz cello note that would just be a sine wave so how is it that instruments ,voices sound different?
No, it's still the harmonic series. The point is that you have a different ratio of amplitudes across the spectrum for different timbre. So different harmonics will be more pronounced for different instruments (all harmonics are still there in all cases, just to varying degree) .

And no, it's not true that a real note from an instrument produces a sine wave. Sine waves are an ideal. Like I said earlier, their is really a distribution of frequencies, which doesn't look anything like a sine wave. Even before you consider harmonics, you can't really just strike one exact note, there will be a small distribution around that note. Then a bunch of harmonics, depending on the physical properties of the resonating body (String, drum membrane, flute cavity, whatever...)

Why doesnt the voilin bowed sound like a guitar being picked continuously
picking delivers an impulsive force (very fine point in time and space) followed by letting it ring... even when you're doing tremolo, the small space between picks is sufficient and still doesn't compete with the constant agitation of the bow. Bowing imparts a friction force (spread across time and space). The friction between the bow and the string causes little super-tiny impulses to be delivered smoothly. Even between impulses of some particular chunk of surface contact, there's always another area of contact causing another impulse, so you get a sustain.

So basically one big, slow pick vs. thousands of rapid, tiny picks. Much different emergent result.
ymalmsteen887
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Feb21-11, 11:36 PM
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Quote Quote by Pythagorean View Post
No, it's still the harmonic series. The point is that you have a different ratio of amplitudes across the spectrum for different timbre. So different harmonics will be more pronounced for different instruments (all harmonics are still there in all cases, just to varying degree) .

And no, it's not true that a real note from an instrument produces a sine wave. Sine waves are an ideal. Like I said earlier, their is really a distribution of frequencies, which doesn't look anything like a sine wave. Even before you consider harmonics, you can't really just strike one exact note, there will be a small distribution around that note. Then a bunch of harmonics, depending on the physical properties of the resonating body (String, drum membrane, flute cavity, whatever...)


picking delivers an impulsive force (very fine point in time and space) followed by letting it ring... even when you're doing tremolo, the small space between picks is sufficient and still doesn't compete with the constant agitation of the bow. Bowing imparts a friction force (spread across time and space). The friction between the bow and the string causes little super-tiny impulses to be delivered smoothly. Even between impulses of some particular chunk of surface contact, there's always another area of contact causing another impulse, so you get a sustain.

So basically one big, slow pick vs. thousands of rapid, tiny picks. Much different emergent result.
About the violin thing thats not what I meant I am saying they sound different regardless how you play them say you played a violin with a pick and did some rapid picking and then a guitar and then a bango they all sound different. You said because of the different levels in the harmonics then how come when I change the equilizer for my on my guitar amp I can never make it sound like another instrument see this is what i am asking?
Pythagorean
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#45
Feb22-11, 12:07 AM
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Quote Quote by ymalmsteen887 View Post
About the violin thing thats not what I meant I am saying they sound different regardless how you play them say you played a violin with a pick and did some rapid picking and then a guitar and then a bango they all sound different.
Ah, ok. But I already told you the different physical characteristics of the instrument alter the harmonic landscape of any given note.

violins have f-holes and hourglass shape bodies

guitars have round holes and a pear shape

The geometry of the resonance chamber thus has an effect on the sound too. Violins also have shorter length strings at different tensions. There's a variety of different strings you can use for both: nylon and steel are the popular contemporary materials. They all have different resistances to motion as the waves try to bend the strings under tension.

You said because of the different levels in the harmonics then how come when I change the equilizer for my on my guitar amp I can never make it sound like another instrument see this is what i am asking?
Because we're talking about a spectrum a lot more complex than a couple of knobs at discrete locations in the spectrum; there's a time-scale associated with the events, so you'd have to have thousands of equilizers that change with time (to account for attack, decay, and vibrato). You would need a high quality synthesizer to even come close. But even synthesizers can't do the real thing.

Remember that a note is not really just one event. It's a complex architecture of millions of events over different spatiotemporal scales. Your equalizer naively filters the waveform every x milliseconds to eliminate each frequency. There are several micro sound events happening within each note, so you have to consider the function of time.

If you're interested in the math/engineering aspects, here's an example of an attempt to model attack and decay:

http://www.rs-met.com/documents/note...ayEnvelope.pdf
ymalmsteen887
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#46
Feb22-11, 12:21 AM
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Quote Quote by Pythagorean View Post
Ah, ok. But I already told you the different physical characteristics of the instrument alter the harmonic landscape of any given note.

violins have f-holes and hourglass shape bodies

guitars have round holes and a pear shape

The geometry of the resonance chamber thus has an effect on the sound too. Violins also have shorter length strings at different tensions. There's a variety of different strings you can use for both: nylon and steel are the popular contemporary materials. They all have different resistances to motion as the waves try to bend the strings under tension.



Because we're talking about a spectrum a lot more complex than a couple of knobs at discrete locations in the spectrum; there's a time-scale associated with the events, so you'd have to have thousands of equilizers that change with time (to account for attack, decay, and vibrato). You would need a high quality synthesizer to even come close. But even synthesizers can't do the real thing.

Remember that a note is not really just one event. It's a complex architecture of millions of events over different spatiotemporal scales. Your equalizer naively filters the waveform every x milliseconds to eliminate each frequency. There are several micro sound events happening within each note, so you have to consider the function of time.
Ok so a bass guitar would have its own unique qualities seperate form a double bass but what about drums how come you dont have to tune a drum when a song changes key. I heard it doesnt have a tonal quality so is it not made up of integers if not then what. Also what about earthquakes are they the same as white or pink noise?
Pythagorean
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#47
Feb22-11, 12:42 AM
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Quote Quote by ymalmsteen887 View Post
Ok so a bass guitar would have its own unique qualities seperate form a double bass but what about drums how come you dont have to tune a drum when a song changes key. I heard it doesnt have a tonal quality so is it not made up of integers if not then what. Also what about earthquakes are they the same as white or pink noise?
I'm not completely sure about less ideal resonators. I play stringed instruments, so I think about the physics a lot more with strings. Having tonal quality means you can associate a particular frequency with it. Noise is an example of a sound that doesn't have tonal quality (so maybe the harmonics from the drum are approximately as loud as the fundamental).

I don't know about earthquakes.
ymalmsteen887
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#48
Feb22-11, 12:49 AM
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Does anybody else know about the harmonics of a drum and why they are not tonal?
nasu
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Feb22-11, 11:42 AM
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Quote Quote by ymalmsteen887 View Post
Does anybody else know about the harmonics of a drum and why they are not tonal?
Technically, the drums don't have harmonics and some authors would say that they don't have a pitch. What they mean is that the frequencies of the "harmonic" components are not multiple of the fundamental. So when you hit the drum you produce a sound that is a combination of various components but those components are not in harmonic ratio.
ymalmsteen887
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#50
Feb23-11, 03:00 AM
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This is what I was asking at the begging if you have a sound source approaching you at 80 miles per hour and you hear 40hz, what would the frequency be if moitionlesss and when leaving you?

Also say you decide what the pressure is motionless what changes the attenuattion when leaving and coming towards you?
JaredJames
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Feb23-11, 03:41 AM
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Quote Quote by ymalmsteen887 View Post
This is what I was asking at the begging if you have a sound source approaching you at 80 miles per hour and you hear 40hz, what would the frequency be if moitionlesss and when leaving you?

Also say you decide what the pressure is motionless what changes the attenuattion when leaving and coming towards you?
What you are talking about now is the doppler effect and you certainly haven't asked this before.
ymalmsteen887
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#52
Feb23-11, 04:09 AM
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Quote Quote by jarednjames View Post
What you are talking about now is the doppler effect and you certainly haven't asked this before.
I know its called the doppler effect and its relevant to my question about why certain frequencies travel farther than others like if the source is moving away its still producing the samw amount of energy though, right so the lower frequency should travel just as far but not farther, am I wrong?
JaredJames
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#53
Feb23-11, 04:11 AM
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Once again, higher frequencies experience more attenuation than lower ones and so don't travel as far.

I have already been through this with you, multiple times. Now you're asking the same thing all over again.
ymalmsteen887
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#54
Feb23-11, 04:18 AM
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Quote Quote by jarednjames View Post
Not true. It's all about acoustics. One person clapping in a gym sounds different to one person clapping in a stadium.

Read here: http://en.wikipedia.org/wiki/Acoustics


I gave you the links to intensity and energy. You need to read them and ensure you understand them. They explain why waves only travel so far before they "don't matter".


More people clapping gives the perception of more loudness. Again, acoustics.

This is like saying 5 speakers give the same volume as 1 speaker. Although the sound system may show them giving the same output, the actual perceived volume will be louder. (Think of the difference between 2.1 and 5.1 surround sound systems.)


As above, more violins will give you more volume - but it's not a case of doubling the volume as you double the number of violins.
About the violins I meant to say that even if they are tuned perfectly no one person is starting at the exact same time and so the waves are not perfectly in phase and gives an orchestra its characteristic sound.

I read somewhere that all the violins dont contribute much to volume because even if you put two subwoofers in an enclosure the boost is like 3db and thats with bass this becomes less significant the higher in frequency you go.


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