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Ayahuasca
16,232 posts
149 months
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mph999 said: Cock Womble 7 said: So at some RPM, my engine makes my mirror rattle, at others it doesn't?
But if you could just explain it again in English - so I can explain it to my thicko mate... Natural Harmonic Frequency .. Example. An A note on the piano has a frequency of 440 Hz. If i played an A note on another instrument, holding down the a key to take the dampers off the string, it will begin to vibrate, and you will here an A note, from the piano. If you add a 'mass' to the back of the mirror (eg, a lump of 'rubber', it will stop vibrating at idle - problem is, it'll vibrate somewhere else. If you put a big enough mass on, you shift it's natural frequency somewhere outside the rev range of the engine - problem fixed. martin There are lots of keys on a piano and only five notes or so, so why don't all the other strings with that note vibrate when one is struck?
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Justin Cyder
6,570 posts
19 months
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Because they are not the same notes, strictly speaking. A440 vibrates at 440hz whereas A an octave higher vibrates at 880hz. Different resonant frequency.
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ATTAK Z
2,094 posts
59 months
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Ayahuasca said: mph999 said: Cock Womble 7 said: So at some RPM, my engine makes my mirror rattle, at others it doesn't?
But if you could just explain it again in English - so I can explain it to my thicko mate... Natural Harmonic Frequency .. Example. An A note on the piano has a frequency of 440 Hz. If i played an A note on another instrument, holding down the a key to take the dampers off the string, it will begin to vibrate, and you will here an A note, from the piano. If you add a 'mass' to the back of the mirror (eg, a lump of 'rubber', it will stop vibrating at idle - problem is, it'll vibrate somewhere else. If you put a big enough mass on, you shift it's natural frequency somewhere outside the rev range of the engine - problem fixed. martin There are lots of keys on a piano and only five notes or so, so why don't all the other strings with that note vibrate when one is struck? There's only one 'A' note with a frequency of 440 Hz
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Ayahuasca
16,232 posts
149 months
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Justin Cyder said: Because they are not the same notes, strictly speaking. A440 vibrates at 440hz whereas A an octave higher vibrates at 880hz. Different resonant frequency. OK. Why are they called by the same letter then? (knows nothing about music except how to play Frere Jacques on the recorder)
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Justin Cyder
6,570 posts
19 months
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Because they are the same note to our ears, just an octave higher. What they don't share is the same frequency, just a doubling of the same frequency.
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Shaolin
2,105 posts
59 months
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Justin Cyder said: Because they are the same note to our ears, just an octave higher. This is a bit about music that makes no sense to me at all. Same note but sounds different? Then again I have the kind of singing voice that makes woodworm leaves their holes, the two may be connected.
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V8mate
35,312 posts
59 months
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Whatever happened to griffins?
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Ayahuasca
16,232 posts
149 months
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Shaolin said: Justin Cyder said: Because they are the same note to our ears, just an octave higher. This is a bit about music that makes no sense to me at all. Same note but sounds different? makes no sense to me either. Can anyone explain it?
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Justin Cyder
6,570 posts
19 months
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Shaolin said: This is a bit about music that makes no sense to me at all. Same note but sounds different?
Then again I have the kind of singing voice that makes woodworm leaves their holes, the two may be connected. Think of it this way. Listen to any rock & roll record & you can hear a bass guitar & a lead guitar, a key board or any other instruments. The song will usually follow a melodic progression, moving essentially from one note to another in a fairly fixed pattern. In simple songs, what ever the main high pitched instruments play, the bass also plays. Your ear can perceive the high pitch of the guitar/keyboard and the low pitch of the bass playing harmoniously together. Although there's no rule they play the same notes, they usually will at least some of the time - and you can hear that seperation clearly. Nicky Wire is such a bad bass player that he pretty much follows the melody line in any Manics song, so they're always a good example of this.
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McAndy
5,012 posts
47 months
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V8mate said: Whatever happened to griffins? They left via the griffin-door.
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doogz
19,304 posts
57 months
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Justin Cyder said: Because they are not the same notes, strictly speaking. A440 vibrates at 440hz whereas A an octave higher vibrates at 880hz. Different resonant frequency. It'll likely still vibrate though. You're only considering the first mode. If I hit one E string on a guitar, and I'm not holding/damping the other, it'll vibrate too.
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PoleDriver
20,247 posts
64 months
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V8mate said: Whatever happened to griffins? They got their own TV series on BBC3!  HTH
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walm
3,458 posts
72 months
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Ayahuasca said: Shaolin said: Justin Cyder said: Because they are the same note to our ears, just an octave higher. This is a bit about music that makes no sense to me at all. Same note but sounds different? makes no sense to me either. Can anyone explain it? They aren't the "same" note at all. It just has the same name (strictly it doesn't have the same name since "middle C" is different from all the other Cs). It is sometimes referred to as C4 and the one an octave higher as C5. The reason they give them the same name (when it is just "C") is because of the frequency doubling/halving thing. So A4 is the one at 440Hz and A5 (an octave higher) is at 880Hz. They are different notes and sound different. This might help: http://en.wikipedia.org/wiki/Piano_key_frequencies
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GTIR
19,245 posts
136 months
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Talking of vibrations in vehicles. I had an annoying vibration noise in my Mercedes (Yes I know, shocking) that developed at around 75mph after six months of ownership from new. I used to ask everyone that sat in the back if they could find the noise but to no avail. Two annoying years later I asked a chap I collected to listen. He sat there listening and after five minutes pulled out the plastic ashtray insert from the door and held it up. No more noise.  Turns out he was an acoustics engineer consultant for Phillips or DuPont or somesuch. 
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walm
3,458 posts
72 months
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doogz said: Justin Cyder said: Because they are not the same notes, strictly speaking. A440 vibrates at 440hz whereas A an octave higher vibrates at 880hz. Different resonant frequency. It'll likely still vibrate though. You're only considering the first mode. If I hit one E string on a guitar, and I'm not holding/damping the other, it'll vibrate too. That's right. That's part of the reason why all the strings/twangy things in a piano have dampers. If you press the damper pedal and play middle C the other Cs will get terribly excited.
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whatnow
1,026 posts
47 months
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Is Hewitt really Prince Harry's father?
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Papa Hotel
10,015 posts
52 months
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Why don't irons have on/off switches?
So much conflicting crap when I Google it, I know there must be the director of an iron company here who can answer correctly.
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V8mate
35,312 posts
59 months
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Papa Hotel said: Why don't irons have on/off switches?
So much conflicting crap when I Google it, I know there must be the director of an iron company here who can answer correctly. So you bloody don't leave it plugged in, see.  Director of bloody big iron company
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DrTre
12,428 posts
102 months
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What are the little boxes on tube platforms, bolted to the wall at just above ankle level? They look like little orange lensed cameras? THeyr'e spaced about 5 m apart.
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Carthage
3,010 posts
14 months
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Is it possible that my neighbour's pet 'dog' is a Chupacabra?
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