Sunday, March 18, 2012

Tube Zither

• a tube , cardboard ABS plastic, and bamboo all work
• heavy mono filament fishing line 80-100 lb test.
• 1'' wood screws
• small eye screws
• hard board
• 1x2'' or 3/4'' dowel

• drill with small drill bits
• hot glue gun
• fin toothed wood saw

The first step to making a tube zither is laying out the where the hole will be drilled so the string will be relatively straight.

We used a piece of wood to mark a ring around the tube about 1 1/2'' from the top and bottom of the tube.

Then we used a door jam to make four parallel line along the the length of the tube, we will drill holes at or near where the line cross the rings around the ends of the tube.

Next drill some pilot holes for your screws, we opted to put the wood screws in a straight line and the eye screws on an angle for a long low string and a shorter high string.

If you choose to use a soft material like cardboard hot glueing some backing plates (1'' squares of hardboard) inside the tube for the screws to screw into will prevent them from pulling through the tube material.

Add wood screws at one end of the zither and the eye screws at the other and tie the mono filament between them. Tie the mono filament to the eye screws before screwing them all the way in so the act of screwing them down will tighten the strings  Finally, to make your zither playable add a bridge under each string made of a small piece of dowel or 1x2'' with a groove filed or sawed into it.

This instrument is very versatile and can be easily tuned to written musical scales, by tightening or loosening the strings or by moving the bridges around to change the effective string length. In our initial experiments we found that ABS actually works better than cardboard for the zither body producing a louder clearer sound. However, cardboard is a close second in terms of sound quality with the advantage of being easy to find. We assume using actual bamboo would produce the best results, but its potential to crack might not make it worth it.

Here's a video:

Siren Disk

• approx. 8'' 1x2'' wood
•  card stock (about 8'' square) or a stiff paper plate
• 3 AA battery holder ( available from item # 92477)
• 2-5k potentiometer (available from online electronics suppliers)
• switch (optional)
• small dc motor (about 3/4'' dai.)
• 1/8'' vinal tubing x18'' (not shown)

• drill with bits that are near the size of your motor and optionally you potentiometer (we like Forstner bits for this application)
• hot glue gun
• hole punch
• scissors or a utility knife
• soldering iron (optional but will make the siren disk more reliable)
• compass
• saw

Make the disk
Use a compass to draw an approx. 7-8'' circle on you card stock or in the center of your paper plate. Cut the circle out and then add the holes (at least 10) with a hole punch.  By pushing the paper into the punch as deep as it will go you will end up with a perfect circle of holes, while you don't want your holes to be bunched together its not a problem if they're not perfectly spaced around the disk. Finally, using a thumbtack mark the center of the disk, add another small piece of card stock on top and hot glue it down to reinforce the center hole.

Make the handle 
Cut about 8'' of 1x2'' and drill a hole for your motor about 1'' from one end.  If you have the right sized Forstner bits, drill out a pocket for you potentiometer, as it will be much more secure than just attaching it to the surface.

Add your components  
Wrap the motor with a little tap until it will press fit into the hole at the top of the handle.  Next hot glue the potentiometer into its pocket below the motor (if you didn't make a pocket be generous with the glue.)  Scratch up the bottom of the battery holder with a nail and then glue it below the potentiometer. connect you components like so :

We ended up using, 3 AA batteries  (4.5v) and a 5k potentiometer while this functioned, the control only worked at one end of the scale, going to a <5k potentiometer or using 4 AA batteries (6v) with a 5k potentiometer would probably make for smoother results (see this site for specifics on rheostats).   Soldering the wires and adding a switch or an alligator clip to the circuit will make it more reliable and less likely to run itself out of power if you forget to disconnect it, but are not necessary.

Use it 
Slowly turn up the power on the potentiometer while blowing through the vinyl tube and aiming at the ring of holes. 

Things to do and notice
 Blowing through the spinning disk acts like a valve alternatively letting air through and deflecting it, emitting pulses of air much like the reads of a straw oboe.  The harder you blow and the closer the tube is to the disk the louder the sound will be.  The speed of the disk, the number of holes passing the tube in a given amount of time determines the frequency of the sound waves and thus the pitch.  The faster it turns the higher the pitch.  The main difference between this and an instrument like a straw oboe and a siren disk is that the disk lacks a resonator.  However, you can make one by holding a piece of pvc pipe (less than 6'') opposite the tube while blowing through it and changing the speed, the sound will get much louder when the resonant frequency is reached. You could also add a paper cone or the cut off top of a bottle as a horn and place it opposite the tube to make it louder. Adding a horn does not really function as a resonator but instead makes the air coming through the disk more efficiently transfer vibration to the surrounding environment as it does in a wind instrument.

The variations of siren disk mechanism can be found in things as small as party favors (siren whistles), and as large as air raid sirens, the main difference is the about the amount and pressure of the air being forced through the chopper disk or drum.             

Thumb Piano

• 1x2'' wood
• small Popsicle sticks, or plastic stirrers
• 3/16 x 2'' inch machine screws or carriage bolts.
• wing nuts

• small saw
• drill and 3/16th bit
• screw driver

Constructing the Thumb Piano is very simple, cut the 1x2'' to length (5-8'') and then drill a hole with the correct sized bit centered and about an inch from the ends of both pieces. Use the machine screws to hold the two piece loosely together.  You can use 2 wing nuts or one regular nut and one wing nut.
Insert the popsicle sticks with different lengths sticking out of the 1x2'' sandwich and tighten the nuts until the sticks don't sound buzzy when plucked. If you want to adjust the sticks you only need to loosen one nut, this is why the second wing nut isn't really necessary.

 The same basic rule about tone that applied to the wind instruments applies to the Thumb Piano the longer the resonator in this case the sticks the lower the note it will produce. For more dramatic example of this try pressing a yard stick or dowel firmly to the edge of a table and plucking the end.  The more the stick hangs off the edge of the table the lower note it will produce, hanging less off of the table will produce a higher note.

Here is another version using some plastic stir sticks we found:

Using the thumb piano
Most people's initial reaction to this thumb piano is that it doesn't work, alone it will only play very softly.  However, press it up against any hardish surface and suddenly it plays very clearly as the object will carry the vibration over a larger area giving it more air moving power. However, not all things will transmit sound equally, and it can be an interesting experiment to find what materials work best and worst to amplify the Thumb Piano and then look at those materials similarities and differences.

Another option is electronic amplification, while not practical for large groups it can be interesting for demonstration purposes, and can serve as general purpose contact microphone.

You'll need the following items:
Radio Shack mini audio amplifier 
•  pre soldered piezo disk
1/8'' plug with cord, or alternatively you can use the Radio Shack unwired stereo plug and add you own wires but the quality can sometime be lacking.

The basic idea is to connect piezo disk to the ground wire and one of channels of the 1/8'' plug. As the amplifier is mono, if you choose the wrong channel it might not work so switch the wires around until you can hear a sound when you tap on the disk before soldering it.  Once its all together its as simple as taping it to you Thumb Piano or anything else you'd like to amplify.


Here are a few more advanced designs we found:

Here's one employing a grounding bar and a wooden salad bowl.

Here are several examples using various key tine materials, like bike spokes and skewers.

New September 2013!

We have discovered that adding a sound board to the thumb piano (kalimba) improves the sound and fun to be had.

Add a 6 inch piece of 1x6 to the bottom of the lower 1x2:

Countersink the machine screws or carriage bolts about a quarter inch into the bottom piece of wood. This allows the kalimba to lay flat.

This base gives a clear sound and the player something to hold on to. It is a big improvement in the finished project for only about 40 cents more per project.

Let us know if you have any other improvements!

Wednesday, March 7, 2012

Ongoing Sound Experiments

Tube Zither 

This is our attempt to replicate a Valiha, a type of zither from Madagascar usually made using a piece of bamboo.  We pre-drilled small holes in a piece of abs pipe we had laying around and used wood screws and eye screws attach the strings just like in the canjo. We put a small pieces of wood on the point of the screws were sticking into the pipe (not visible) and used similar small blocks of wood with grooves in them to function as bridges.  The first test produced a soft but clearly audible sound, that could be adjusted by moving the bridges, tightening or loosening the strings or figuring them like a guitar.  As the tube functions as both the resonator and the neck of the instrument its a very simple and versatile.  We will try to make a more standard model employing a cardboard tube in the near future and will post instructions when we do.  

Tube trumpet

Some times referred to as a Hosaphone, there are hundreds of different examples online.  That said we don't claim to be doing something new here, but instead were trying to figure out the nuances.  We started with 28'' of 5/8'' and 67'' of 1/2'' vinyl tubing and then started changing the mouth pieces and horn bells to see how it would effect the sound.  With out any modifications we were able to get 5-6 tones out of the trumpet consistently.  Below are some of the horn we tried:

the 3/4 2 liter resulted in a clear but muffled tone, the water bottle was buzzy and had the added feature of being squish-able which sounds sort of like a mute on a trumpet, the vitamin water bottle sounded very much like a stadium horn (Vuvuzela) and the straight cone made the clearest tone. The 3/4 2 liter seemed to make playing hight notes difficult.

Here's the tube with a mute (a 2 liter bottom) and some mouth pieces we tried. The small section of larger vinyl tubing as a mouthpiece is playable, but a small section of pvc worked better, but not great.  Given the success the pvc we tried boring out the inside of a identical pvc pipe to make the opening bigger, this resulted in an even more playable mouthpiece. I noticed that you could get higher notes more easily with this mouth piece.  Hoping this trent of wider and stiffer would be better we tried gluing the very top section of a 2 liter to a pvc pipe to make a super wide mouth piece, this was did not work as planed.  The horn was very easy to sound, but getting high notes was nearly impossible, as you couldn't close your lips tight enough with the wide opening .    
Given the surprising variety of results planning an activity based on making a curtain timbre (character of sound) with a tube trumpet or similar instrument might be possible in the future.      

Sound Automata: Drum Machine

   This is our first attempt at programable sound automata, a drum machine.  It consists of a cardboard tube you can rotate with a crank, into this drum you can add tacks at various intervals to strike the drum sticks and create a rhythm.

Here's the automata in action playing on a tea tin (sorry for the uninspired rhythm).
We plan to develop a few standard models of this and post them in the future, stay tuned.

Thursday, March 1, 2012

PVC Slide Whistle

The pvc slide whistle is a modification to the pvc steam whistle which allows multiple tones to be produced  by changing the length of the whistle tube with a piston, just like a toy slide whistle.   Here are the additional items you need to turn a pvc steam whistle into a pvc slide whistle. 

•a 1/2'' pvc steam whistle (6-8'' long from the bottom of the whistle mouth)
• a large chop stick
• a 00 size rubber stopper
• 3/8''id, 1/2''od vinyl tubing (about 1/2'' long)
• 1/2'' pvc pipe cap

• a drill with 1/4'' bit (or one at lease the size of you chop stick)
• hot glue gun

To make a piston we took a large chop stick (about 1/4'') and sharpened it in a pencil sharpener, then  poked it into the small end of a 00 size rubber stopper and hot glued it in place, being careful that it was on straight.

To make a perfect seal inside the pipe we put a small piece of 3/8'' id, 1/2'' od vinyl tubing over the stopper.  By test fitting the piston into the pipe and pushing it further onto the stopper to stretch it slightly you can get a really good seal.

To put it all together drill a hole in the center of the pvc cap put the chop stick through and then put the piston in the whistle and the cap on the end to keep it straight and prevent jamming.  Whistles with chambers of 6-8'' seemed to work well for 1/2'' pvc pipe. You will be able to get lower notes with a longer 3/4'' pipe without over blowing.  

Things to do and notice:
Other than being fun to play with and an instrument you can learn to intuitively play melodies on the nature of a slide whistle can show you a lot about how the dimensions of the whistle effect the sound it produces.  The obvious effect is that by lengthening or shortening the whistle by moving the piston you can lower or raise the note it produces. The more interesting information you can glean from a slide whistle is how hard or soft you have to blow to get a natural note without over blowing. We found, as the steam whistle resources suggest, that the further out the piston is the softer you had to blow to avoid an overtone. The only way to avoid this is lower the length to diameter ratio by making the whistle wider. Interestingly enough we also found that if you push the piston in too far (which is not all the way in) the whistle stops sounding and the only way to solve this is to make the whistle narrower. When you think about the sizes of high and low pitched wind instruments, say a fife vs a bassoon, you realize that people  have had this figured out for a long time, but you don't usually see it in one instrument.