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== Age ==
{| class="wikitable" style="color:black; background-color:#ddd; margin-left: auto; float:right"
| [[Physics]]:
| Sound Waves, Parts of a Wave
|-
| Grade Range:
| [[Elementary School]], [[Middle School]], [[High School]]
|-
| Format:
| [[Stage]]
|}


Elementary School, Middle School, High School
This features our six foot Reuben's Tube, and is a very impressive demonstration on sound waves. this demonstration is a popular request, and is easily adapted to present to a variety of audiences.
 
==Format ==
 
Stage Show


== Materials ==
== Materials ==


    Flame tube
* Flame Tube w/Hose
    Propane tank
* Propane Tank
    Speaker
* Speaker w/Amplifier
    Tone generator
* Tone Generator w/Cable
    Amplifier
* Headphone Jack Cable
    MP3/CD player
* Lighters (2)
    Cord for portable music player
* Power Strip
    Lighter
* Extension Cord
* Optional: Keyboard w/Cable Adapter


== Safety Precautions ==
== Safety Precautions ==


Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience.
Read the Fire Safety section of the [[Demonstration Safety]] Page before using this demonstration.


This demo of course involves fire so be sure to have a fire extinguisher handy as well as keeping the audience a safe distance from the tube itself. Be sure to turn off the propane when done! After the demo, tilt the tube to one end and light the remaining propane to burn it away. You can place one side of the tube on top of the speaker box; this set up seems fairly stable and hasn’t failed us yet. As a word to the wise, be careful where the feet of the tube are as they may slide as you pick one end of the tube up.
This demonstration requires: Safety Glasses


== Preparation ==
This demonstration is sensitive to wind, so do not use outdoors or in a breezy room. In order to present this demonstration, you will need two tables to set up.
 
Make sure the propane tank is full as well as having lighters that are full.


== Demonstration ==
== Demonstration ==


Once the propane tank is connected to the flame tube, turn the tank on and begin lighting the holes closest to the hose. Once all the holes have been lit, you can play a tone through the tube. Play several different tones as to demonstrate the different wavelengths and frequencies. We currently use the frequencies 206Hz and 412Hz and they seem to work pretty well. As a finale, play some music through the tube to show how all the different frequencies appear through the tube. “Iron Man” by Black Sabbath has worked well in the past and seems to fit the visual of fire, though others will work well, too.
;Preparation:
 
Set the Flame Tube on the first table, with both sets of feet resting on the same table. On the second table, set the speaker next to the Flame Tube, putting the speaker about half an inch away from the cellophane seal on the side of the tube, or as close as it can get without touching. Next to the speaker, place the amplifier and tone generator. Connect the tone generator cable to the amplifier using the back port labeled "Phono", and the audio cable in the "Aux" port. Put the switch for the ports in the "Phono" position. Make sure the main volume for the speaker is at zero, then plug in the amplifier and tone generator and turn them both on. Connect the propane tank to the flame tube, and before the start of the presentation open the propane tank fully. Attempt to ignite the holes on top of the propane tank once every minute, and once lit let it stand so the flames can grow.
== What to Say ==
 
Traditionally, this demo follows a presentation about waves, normally with the use of slinkies. This is not a requirement, but it makes things easier.
 
"When I say the word “waves” what do you think of? (Allow for answers, we’re looking for anything wave related including light, sound, radiation or water. Water is what we will go with to continue the presentation) Yeah, water like at the beach right? What do those look like? Perfect, up and down, you got it. There are actually two types of waves; transverse: up and down like water, and longitudinal: side to side. "
 
"What we're going to do now is actually show you these waves using slinkies! Can I get a volunteer? (Use the volunteer to demonstrate the different waves just mentioned. Laying the slinky down on the floor, hold one end and have them shake their end from side to side to make transverse waves; hold your end and have them push theirs in toward you and back out to make a longitudinal wave) When we move the slinky up and down we can see what we called “transverse” waves earlier. If we push in on the slinky we can get the waves to move side to side. Does anyone remember what these waves were called? Longitudinal, great! These are a little harder to see, but you can see that the slinky gets really close together at some points, and really far apart at others. (Perhaps demonstrate some of the later concepts such as amplitude, etc. by making the waves bigger or smaller, etc.) Thanks you can go sit back down!" (You may even want to use two different volunteers for each wave to increase participation.)
 
"When we think about this wave (we’ll use a transverse one being made by a slinky for now) what are some ways we could describe it? How big it is, how long it is, how quickly it moves, how many of them there are? Those are all perfect. For starters, let’s look at how many waves there are. This is called the frequency. So you can think of frequency as the number of waves; high frequency: lots of waves, low frequency: not so many waves. Another property we can talk about is how long the wave is. If we look at this length here, the length between the top (peak) here and the top here, that is called the wavelength. Makes sense right, the length of a wave is the wavelength? Perfect. So if you notice, when we increase the frequency, we decrease the wavelength. If you want to squeeze more waves in to the same amount of space, they need to get smaller. Everyone see that? Great. Now, there is another property we can talk about, and that is how big this wave is. This is called the amplitude, a big movement is a big amplitude and a little movement is a little amplitude."
 
"So now you’re all wave experts right? Exactly. So, let’s talk about sound. Sound travels as a wave, but not an up and down wave like the slinky. Nope, sound travels side to side. Does anyone remember what that was called? It’s not transverse, it starts with an “l”…Right! Longitudinal. Sound is a longitudinal wave, not only that, but sound is a compression wave. Sound travels by compressing the molecules as it travels. It is a little hard to visualize, but longitudinal waves have all the same properties that we just talked about. They have a frequency: the number of waves, they have a wavelength and they have an amplitude. Now, when it comes to sound, those properties have an effect on what we hear. Let’s start with the easy one, amplitude. What do you think a big amplitude means with a sound? Right, it’s bigger or louder. So amplitude tells us how loud the sound is. Frequency is a little hard to guess, so I’ll give you a hint. The number of waves helps us change how the sound “sounds”. Any guesses? Right, higher or lower pitch/tone. So a high frequency is a higher pitch and a low frequency is a lower pitch. "
 
"So before with the slinky, you could see everything changing, right? Can you guys see sound waves? No, not really. So what we’ve got here is a way to help you visualize sound waves. Let me explain this contraption here. We have this long metal tube, connected to a propane tank and it has a bunch of little holes in the top. So when we fill this up with propane, we can light the gas off the top and it will look like a row of candles. Next to that, we have our speaker, hooked up to a tone generator and an amplifier [these may be unfamiliar words to the audience, so be sure to take extra time to explain just what is going to happen, e.g. “When we turn all this on, this speaker is going to play a single note which will travel through this tube. The tone generator lets me change the pitch from higher to lower (this would be a good time to actually demonstrate the different pitch before lighting the flame tube, so they understand what you're going to be doing). Now we're going to light all the propane.”] So, what do you think this will look like if we play a note from this speaker down the tube? Let’s take a look.


"So what did it look like? Yeah, like a bunch of waves! Let’s look again. See the high spots and low spots? Those correspond to areas of high compression and low compression. Ok, so that was one frequency. What do you think will happen if I change the frequency? I’ll give you a hint; I’m going to increase it. Right, there will be more waves! See, just like you said; increase the frequency, increase the number of waves."
;Presentation:
# Explain briefly the setup you are using; A speaker system is set against the Flame Tube, and by turning on the speaker you will put a sound wave through the tube, which we will see as a Transverse wave in the fire. This is because of the sound compressing the propane gas inside the tube.
# Set the tone generator to 210Hz, and turn up the speaker volume to 1/2 full. The flames will move, creating the wave!
# Turn down the speaker volume, and name the parts of the wave: Peak (high point), Trough (low point), Node (mid point), Amplitude (height), Frequency (note heard), and Wavelength.
# Ask the audience what will happen if we turn up the volume. Show that the amplitude increases, and therefore the amplitude is how ''loud'' a sound is.
# Ask the audience to vote on this: If you doubled the frequency (or "went up an octave"), should we see ''more'' waves or ''less'' waves? After getting responses, set the tone generator to 420Hz and turn the volume up 1/2 full. The number of waves will double! What kind of relationship do frequency and wavelength have?
# Flip the switch on the back of the amplifier to "Aux". Connect your phone or music player, and select a song to play for them! Songs that work well are:
#* Secrets (OneRepublic)
#* Let it Go (from Frozen)
#* Photograph (Ed Sheeran)
#* Fly Me to the Moon (Frank Sinatra)
#* Iron Man (Black Sabbath)
#* Stay the Night (Zedd, Haley Williams)
#* Bangarang (Skrillex)
#*''NOTE: Use the two lighters to keep re-igniting the propane while you have a song playing. The music will put out flames as it plays. Only play 30-45 seconds of any one song, so that you can play a few different songs.''
# When you finish presenting the Flame Tube, turn off the propane tank and detach it. Place the speaker on its side, and prop the flame tube on it, with a set of feet resting on the speaker. Ignite the propane coming out of the lower end of the tube, and let it burn off until it is time to pack up.


"Ok, so that is just one single note. How often does that happen in real life? Yeah, not too often. So what do you think will happen if we play something like music? Let’s take a look. Pretty cool stuff right?"
== Why It Works ==


== Why It Is ==
This demonstration introduces ''Waves'', which are a type of oscillation that accompanies an energy transfer. Sound Waves are ''Compression'' waves, which travel with an in-and-out motion through a medium. By using the flame tube, we are transforming the compression waves into transverse waves, so to make it easier to identify the different parts of the waves. When we look at the transverse wave we made with the flame tube, we can see that there are high points and low points. The ''Peak'' is the high point, and the ''Trough'' is the low point, with the mid point of the wave being called the ''Node''. The height of a wave is the ''Amplitude'', which is often shortened to amp. To make a wave taller or shorter, you have to adjust the volume, or amps. The distance from one peak to the next is the ''Wavelength'', which with sound we can recognize it as a note. To change the note heard, you have to increase or decrease the wavelength. The ''Frequency'' of a wave is the inverse of the wavelength. A way to think of it is that the frequency is the number of waves per second. If you start at Center C on a piano and go up an octave, you are ''doubling'' the frequency of that note. Frequency and wavelength are inverse to each other, so when you double the frequency, you cut the wavelength in half! Likewise, if you cut the frequency in half, you would double the wavelength.


Sound waves travel through the air as vibrations referred to as “longitudinal waves”. This just means that the waves oscillate in the direction in which they are travelling. Because of this, they bunch up in some areas and are more spread out in others. When this happens inside the tube, this causes the propane to be compressed in certain areas and as a result it gets forced out of the tube with more pressure. This greater pressure creates a larger flame.
{| class="wikitable" style="color:black; background-color:#ddd; text-align: center; margin: auto"
|+
|-
|'''Peak''':
|'''Trough''':
|'''Node''':
|'''Amplitude''':
|'''Wavelength''':
|'''Frequency''':
|-
|Highest Point
|Lowest Point
|Mid Point
|Height of Wave
|Distance from Peak to Peak
|Number of waves over a set distance
|}


== Real Life Examples ==
When we listen to music, we know that there are a lot of notes in the music working together or against each other. By playing a song through the Flame Tube, you can see how some notes work together, creating really high flames or easy-to-see waves. You can also see where the notes don't work together, when certain spots in the flame tube get really low flames, or get put out! When the notes are working together, we are seeing ''constructive interference'', or interference that adds onto each other and amplifies. When the notes clash, we are seeing ''destructive interference'', or interference that subtracts from each other and diminishes.


Sound waves
== Additional Information ==
* This demonstration can have the [[Slinky Waves]] as an optional opening demonstration.
* Try to avoid using the Flame Tube at the end of a show, and to not run the Flame Tube for any more than 25 minutes at a time. This is to minimize any fire hazard, and to allow time for the flame tube to empty after a presentation.

Latest revision as of 22:25, 23 May 2016

Physics: Sound Waves, Parts of a Wave
Grade Range: Elementary School, Middle School, High School
Format: Stage

This features our six foot Reuben's Tube, and is a very impressive demonstration on sound waves. this demonstration is a popular request, and is easily adapted to present to a variety of audiences.

Materials

  • Flame Tube w/Hose
  • Propane Tank
  • Speaker w/Amplifier
  • Tone Generator w/Cable
  • Headphone Jack Cable
  • Lighters (2)
  • Power Strip
  • Extension Cord
  • Optional: Keyboard w/Cable Adapter

Safety Precautions

Read the Fire Safety section of the Demonstration Safety Page before using this demonstration.

This demonstration requires: Safety Glasses

This demonstration is sensitive to wind, so do not use outdoors or in a breezy room. In order to present this demonstration, you will need two tables to set up.

Demonstration

Preparation

Set the Flame Tube on the first table, with both sets of feet resting on the same table. On the second table, set the speaker next to the Flame Tube, putting the speaker about half an inch away from the cellophane seal on the side of the tube, or as close as it can get without touching. Next to the speaker, place the amplifier and tone generator. Connect the tone generator cable to the amplifier using the back port labeled "Phono", and the audio cable in the "Aux" port. Put the switch for the ports in the "Phono" position. Make sure the main volume for the speaker is at zero, then plug in the amplifier and tone generator and turn them both on. Connect the propane tank to the flame tube, and before the start of the presentation open the propane tank fully. Attempt to ignite the holes on top of the propane tank once every minute, and once lit let it stand so the flames can grow.

Presentation
  1. Explain briefly the setup you are using; A speaker system is set against the Flame Tube, and by turning on the speaker you will put a sound wave through the tube, which we will see as a Transverse wave in the fire. This is because of the sound compressing the propane gas inside the tube.
  2. Set the tone generator to 210Hz, and turn up the speaker volume to 1/2 full. The flames will move, creating the wave!
  3. Turn down the speaker volume, and name the parts of the wave: Peak (high point), Trough (low point), Node (mid point), Amplitude (height), Frequency (note heard), and Wavelength.
  4. Ask the audience what will happen if we turn up the volume. Show that the amplitude increases, and therefore the amplitude is how loud a sound is.
  5. Ask the audience to vote on this: If you doubled the frequency (or "went up an octave"), should we see more waves or less waves? After getting responses, set the tone generator to 420Hz and turn the volume up 1/2 full. The number of waves will double! What kind of relationship do frequency and wavelength have?
  6. Flip the switch on the back of the amplifier to "Aux". Connect your phone or music player, and select a song to play for them! Songs that work well are:
    • Secrets (OneRepublic)
    • Let it Go (from Frozen)
    • Photograph (Ed Sheeran)
    • Fly Me to the Moon (Frank Sinatra)
    • Iron Man (Black Sabbath)
    • Stay the Night (Zedd, Haley Williams)
    • Bangarang (Skrillex)
    • NOTE: Use the two lighters to keep re-igniting the propane while you have a song playing. The music will put out flames as it plays. Only play 30-45 seconds of any one song, so that you can play a few different songs.
  7. When you finish presenting the Flame Tube, turn off the propane tank and detach it. Place the speaker on its side, and prop the flame tube on it, with a set of feet resting on the speaker. Ignite the propane coming out of the lower end of the tube, and let it burn off until it is time to pack up.

Why It Works

This demonstration introduces Waves, which are a type of oscillation that accompanies an energy transfer. Sound Waves are Compression waves, which travel with an in-and-out motion through a medium. By using the flame tube, we are transforming the compression waves into transverse waves, so to make it easier to identify the different parts of the waves. When we look at the transverse wave we made with the flame tube, we can see that there are high points and low points. The Peak is the high point, and the Trough is the low point, with the mid point of the wave being called the Node. The height of a wave is the Amplitude, which is often shortened to amp. To make a wave taller or shorter, you have to adjust the volume, or amps. The distance from one peak to the next is the Wavelength, which with sound we can recognize it as a note. To change the note heard, you have to increase or decrease the wavelength. The Frequency of a wave is the inverse of the wavelength. A way to think of it is that the frequency is the number of waves per second. If you start at Center C on a piano and go up an octave, you are doubling the frequency of that note. Frequency and wavelength are inverse to each other, so when you double the frequency, you cut the wavelength in half! Likewise, if you cut the frequency in half, you would double the wavelength.

Peak: Trough: Node: Amplitude: Wavelength: Frequency:
Highest Point Lowest Point Mid Point Height of Wave Distance from Peak to Peak Number of waves over a set distance

When we listen to music, we know that there are a lot of notes in the music working together or against each other. By playing a song through the Flame Tube, you can see how some notes work together, creating really high flames or easy-to-see waves. You can also see where the notes don't work together, when certain spots in the flame tube get really low flames, or get put out! When the notes are working together, we are seeing constructive interference, or interference that adds onto each other and amplifies. When the notes clash, we are seeing destructive interference, or interference that subtracts from each other and diminishes.

Additional Information

  • This demonstration can have the Slinky Waves as an optional opening demonstration.
  • Try to avoid using the Flame Tube at the end of a show, and to not run the Flame Tube for any more than 25 minutes at a time. This is to minimize any fire hazard, and to allow time for the flame tube to empty after a presentation.
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