Sounds Of Music C

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Re: Sounds Of Music C

Post by smayya337 » March 15th, 2019, 11:36 am

I took way too long to post a question, so here's one.
I don't know how long my clarinet is and I'm too lazy to get it from the band room. If its lowest note is equally-tempered D3, how long should I expect it to be?
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Re: Sounds Of Music C

Post by wec01 » March 15th, 2019, 11:50 am

smayya337 wrote:I took way too long to post a question, so here's one.
I don't know how long my clarinet is and I'm too lazy to get it from the band room. If its lowest note is equally-tempered D3, how long should I expect it to be?
Assuming the speed of sound is about 343 m/s:
Since a clarinet has a node at one end and antinode at the other, the length would be approximately c/4f or, in this case:
[b]58.4 cm[/b]
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

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Re: Sounds Of Music C

Post by smayya337 » March 15th, 2019, 11:51 am

wec01 wrote:
smayya337 wrote:I took way too long to post a question, so here's one.
I don't know how long my clarinet is and I'm too lazy to get it from the band room. If its lowest note is equally-tempered D3, how long should I expect it to be?
Assuming the speed of sound is about 343 m/s:
Since a clarinet has a node at one end and antinode at the other, the length would be approximately c/4f or, in this case:
[b]58.4 cm[/b]
That was fast... Almost like you were next to me when I wrote this problem lol
Math checks out, your turn!
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Re: Sounds Of Music C

Post by wec01 » March 15th, 2019, 12:36 pm

You have purchased a slide whistle that is 30 cm from the lip to the slide when it is pulled all the way out.
1. What frequency does it play in this position?
2. How far should you move the slide up in order to play A4?
3. Approximately what frequency would the whistle play if the slide is removed? (use 30 cm as the length)
2019 Division C Nationals Medals:
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5th place Sounds of Music
2nd place Thermodynamics

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Re: Sounds Of Music C

Post by mjcox2000 » March 25th, 2019, 6:23 am

wec01 wrote:You have purchased a slide whistle that is 30 cm from the lip to the slide when it is pulled all the way out.
1. What frequency does it play in this position?
2. How far should you move the slide up in order to play A4?
3. Approximately what frequency would the whistle play if the slide is removed? (use 30 cm as the length)
These answers assume 3 sig figs on the 30cm length, since it’s usually easy to measure lengths on this scale to 3 sig figs. 
1. The tube is open at one end and closed at the other, so wavelength is 4 times length. [math]\frac{343\, m/s}{4\cdot 30\, cm}=\boxed{286\, Hz}[/math]
2. The wavelength of A4 is 78.0 cm, so the tube length is [math]\frac{78.0\ cm}{4}=19.5\, cm[/math], so the slide must be moved up [math]\boxed{10.5\, cm}[/math]
3. Now the tube is open at both ends, making wavelength 2 times length. [math]\frac{343\, m/s}{2\cdot 30\, cm}=\boxed{572\, Hz}[/math]
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Re: Sounds Of Music C

Post by wec01 » March 25th, 2019, 6:27 am

mjcox2000 wrote:
wec01 wrote:You have purchased a slide whistle that is 30 cm from the lip to the slide when it is pulled all the way out.
1. What frequency does it play in this position?
2. How far should you move the slide up in order to play A4?
3. Approximately what frequency would the whistle play if the slide is removed? (use 30 cm as the length)
These answers assume 3 sig figs on the 30cm length, since it’s usually easy to measure lengths on this scale to 3 sig figs. 
1. The tube is open at one end and closed at the other, so wavelength is 4 times length. [math]\frac{343\, m/s}{4\cdot 30\, cm}=\boxed{286\, Hz}[/math]
2. The wavelength of A4 is 78.0 cm, so the tube length is [math]\frac{78.0\ cm}{4}=19.5\, cm[/math], so the slide must be moved up [math]\boxed{10.5\, cm}[/math]
3. Now the tube is open at both ends, making wavelength 2 times length. [math]\frac{343\, m/s}{2\cdot 30\, cm}=\boxed{572\, Hz}[/math]
That's true, I probably should've specified more sig figs
Everything looks good, your turn
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

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Re: Sounds Of Music C

Post by mjcox2000 » March 28th, 2019, 7:26 am

Anna hears a buzzing sound when she plays a low C on her marimba, but not when she plays other notes. What are some things she should check to figure out what’s causing the buzzing sound?
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Re: Sounds Of Music C

Post by wec01 » March 31st, 2019, 8:24 pm

mjcox2000 wrote:Anna hears a buzzing sound when she plays a low C on her marimba, but not when she plays other notes. What are some things she should check to figure out what’s causing the buzzing sound?
The key could be touching a support and vibrating against it or the chord going through the keys could be too lose (although I think that would affect other keys as well so it's more likely the first issue).
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

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Re: Sounds Of Music C

Post by mjcox2000 » March 31st, 2019, 8:31 pm

wec01 wrote:
mjcox2000 wrote:Anna hears a buzzing sound when she plays a low C on her marimba, but not when she plays other notes. What are some things she should check to figure out what’s causing the buzzing sound?
The key could be touching a support and vibrating against it or the chord going through the keys could be too lose (although I think that would affect other keys as well so it's more likely the first issue).
Having the bar touch a support could certainly be the reason it’s buzzing. (Usually this would be because a rubber spacer on the support fell off). On the other hand, the cord being too small won’t cause it to buzz, since the cord is soft and has plenty of give to it.
Anna checks her marimba for the things you mentioned and discovers that they’re not the problem. What should she check next?
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Re: Sounds Of Music C

Post by wec01 » March 31st, 2019, 8:39 pm

mjcox2000 wrote:
wec01 wrote:
mjcox2000 wrote:Anna hears a buzzing sound when she plays a low C on her marimba, but not when she plays other notes. What are some things she should check to figure out what’s causing the buzzing sound?
The key could be touching a support and vibrating against it or the chord going through the keys could be too lose (although I think that would affect other keys as well so it's more likely the first issue).
Having the bar touch a support could certainly be the reason it’s buzzing. (Usually this would be because a rubber spacer on the support fell off). On the other hand, the cord being too small won’t cause it to buzz, since the cord is soft and has plenty of give to it.
Anna checks her marimba for the things you mentioned and discovers that they’re not the problem. What should she check next?
an issue with the resonators, so she could check to see if the buzzing is still heard when the resonator is blocked.
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

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