Questions for Tim Kaiser

Learn more about my research In March 2009, Tim Kaiser answered visitors questions about sound.

Your Comments, Thoughts, Questions, Ideas

tim's picture
tim says:

the term "true rms" I know what the abb. mean but have a hard time putting it into practice with the rms volt meter i have. Im a electrical trouble shooter with a electric company. I know you can use it to measure the means of diffrent objects including acustics, but dont understand it enough to teach my self to teach others. thanks tim

posted on Wed, 03/04/2009 - 4:28pm
Tim Kaiser's picture
Tim Kaiser says:

Yeah, that's a tough one. The meter you use at work does the conversion for you, but it is only accurate with sine waves. The math behind it is a bit beyond me, but here's the wiki explanation of what the point of measuring it is:
When measuring the value of an alternating current signal it is often necessary to convert the signal into a direct current signal of equivalent value (known as the RMS, root mean square, value). This process can be quite complex (see root mean square for a detailed mathematical explanation). Most low cost instrumentation and signal converters (for example handheld multimeters of the sort used by maintenance engineers) carry out this conversion by filtering the signal into an average value and applying a correction factor.

The value of the correction factor applied is only correct if the input signal is sinusoidal. The true RMS value is actually proportional to the square-root of the average of the square of the curve, and not to the average of the absolute value of the curve. For any given waveform the ratio of these two averages will be constant and, as most measurements are carried out on what are (nominally) sine waves, the correction factor assumes this waveform; but any distortion or offsets will lead to errors. Although in most cases this produces adequate results, a correct conversion or the measurement of non sine wave values, requires a more complex and costly converter, known as a True RMS converter.
Not the best answer, but my own knowledge is what it is!

posted on Thu, 03/05/2009 - 3:19pm
ARTiFactor's picture
ARTiFactor says:

I remember building a ring modulator for a synthesizer back in the mid 70s.. I used it to make bell or gong like sounds. What was being done to the input signal (maybe use a square wave as an example) or were there two input signals? Some of my memories from those days are kind of fuzzy.

posted on Wed, 03/04/2009 - 5:33pm
Tim Kaiser's picture
Tim Kaiser says:

Ring modulation is a way to achieve amplitude modulation or frequency mixing by multiplying two signals- most often it is with a sine-wave, but can be done with a square wave, too. The circuit is similar to a bridge rectifier, except that instead of the diodes facing "left" or "right", they go "clockwise" or "counterclockwise" in a line. It is referred to as "ring" modulation because the analog circuit of diodes is in the shape of a ring. It's only coincidental that the tones created with a ring mod are bell-like in sound.

posted on Thu, 03/05/2009 - 1:38am
ARTiFactor's picture
ARTiFactor says:

Ring modulator
Ring modulatorCourtesy Gablin
Thanks Tim. When we discuss various sounds I wish we could include an audio file so readers could hear what is being discussed. You can hear the effect of a ring modulator by clicking over to this wikipedia page (samples are on the right side).

I will ask Brian K. if there is a way to embed an audio player directly into these comments.

I really love sound science and am so glad you are doing this.

posted on Thu, 03/05/2009 - 1:08pm
Anonymous's picture
Anonymous says:

why are sound waves called sound waves?

posted on Thu, 03/05/2009 - 11:00am
Tim Kaiser's picture
Tim Kaiser says:

Sounds are vibrations that are transmitted through a medium (air, water, solids, etc.). These vibrations move in waves and different kinds of sounds have different wave shapes. We call them waves because they behave similarly to the waves on a body of water. They repeat, fade, elongate and even crash or reflect when they hit something. A device called an oscilloscope can display sound waves in a visual form. Another way to "see" a sound wave is to stretch a really long string so that it is super tight and then pluck it. The vibration you see is the frequency of the sound wave.

posted on Thu, 03/05/2009 - 3:28pm
ARTiFactor's picture
ARTiFactor says:

Gonger
GongerCourtesy ARTiFactor
I bought this "gonger" about 15 years ago. The vender had more than a dozen different shapes which I sampled. Both the shape and the sound for this one were my favorites. By hanging the loop of fish line over fingers placed into each ear and having someone strike the gonger, an incredible sound is heard. (You can hang a fork or coat hanger from a loop of string to try this)

My question is how or why the shape would influence the sound dynamic. I know length is the main factor but I suspect different shapes with the same length would have different sounds. I also know that where the gonger is struck influences the sound.

posted on Fri, 03/06/2009 - 11:45am
Tim Kaiser's picture
Tim Kaiser says:

Length is definitely the main factor. Each segment between bends is also a "length." The fact that they are all connected as one adds another element to the sound coloration. A french horn has only three valves, but the overall length and all those curves add a wider range of tone than what would be possible if it were simply stretched out into one long tube with a bell on the end. The reason this works is that the wall of the tubing is more dense at the bends. In addition (and to a lesser degree) sound waves reflect when they bounce off of something. When a sound wave travels through your gong, it is broken up a bit at every curve. The smaller broken pieces of sound keep moving along with the "main" sound, but their alteration adds to the complexity of the overall tone. With a little experimentation (and some math) you could build a gonger with perfect harmonics by knowing how long each segment before a bend has to be.

posted on Fri, 03/06/2009 - 4:10pm
ARTiFactor's picture
ARTiFactor says:

I just read about a sound generator that won the recent Guthman Musical Instrument Competition at Georgia Tech. There was a $15,000 prize. Maybe you should enter one of your inventions next year. Can you describe a few of your favorites?

Jaime Oliver's Silent Drum Controller is a transparent shell covered with an elastic head that the player can stretch with their fingers. A camera positioned to the side detects the shape of the deformation and translates that into sound.

posted on Wed, 03/11/2009 - 8:51am
Tim Kaiser's picture
Tim Kaiser says:

I've got stuff I'm partial to, but this says it best:

posted on Wed, 03/11/2009 - 10:15pm
ARTiFactor's picture
ARTiFactor says:

Thanks Tim,
This video (with sound) is just what I hoped for. You are indeed a lucky man.

posted on Thu, 03/12/2009 - 9:38am
OliviaB.'s picture
OliviaB. says:

Ohmygoodness gracious! Have you ever thought about selling mass replicas of your work at bulk to the various electronica musicans out there who would give their right leg to incorporate it in their music/performances? Or perhaps the pieces are too specialized to find 1000s of them all at once, eh? Wow. Sure some of us have day jobs (and completely envy you), and can't do music all day, but everyone appreciates a great piece of work/art.
-----------
OliviaB.
San Francisco DUI lawyer

posted on Thu, 04/09/2009 - 1:14pm
Tim Kaiser's picture
Tim Kaiser says:

Part of my motivation is adaptive re-use, so mass replication is outside of my interest. I know other builders who have gone that route and I wish them the best of luck- it's just not for me. Thank you so much for your kind words!

posted on Fri, 04/17/2009 - 3:11pm
Tim Kaiser's picture
Tim Kaiser says:

Come to Make Day this Saturday March 14th 10 am - 3 pm at the Science Museum

http://www.smm.org/makeday/

posted on Fri, 03/13/2009 - 9:58am
Anonymous's picture
Anonymous says:

What is your favoriate instrument you created and why?

posted on Mon, 03/16/2009 - 5:55pm
Tim Kaiser's picture
Tim Kaiser says:

My favorite device is something I call the Green Hornet http://www.timkaiser.org/SONICgreenhornet.jpg
It's a delay circuit housed in an old valve case with beehive lenses on the sides. It was fun to build because it just kind of came together as I was finding pieces. I use it in a lot of my compositions and it has been super reliable over the years.

posted on Tue, 03/17/2009 - 12:09am
Anonymous's picture
Anonymous says:

What inspires you? Is it music, is it science, is it the creative process? Or none of these?

posted on Mon, 03/16/2009 - 5:56pm
Tim Kaiser's picture
Tim Kaiser says:

I guess life is what really inspires me. The process is more important than the end product, though. I love music, art, science- just learning new things in general.

posted on Tue, 03/17/2009 - 12:11am
Anonymous's picture
Anonymous says:

how does sound move

posted on Tue, 03/17/2009 - 12:10pm
Tim Kaiser's picture
Tim Kaiser says:

Sound is matter vibrating. If you pluck a string on a guitar, the energy is transferred as a vibration. Since sound moves in waves, the vibration of the string makes the air around it vibrate. The sound waves travel through the air and into your ear, where the ear drum vibrates and sends that signal to your brain.

posted on Tue, 03/17/2009 - 3:32pm
Anonymous's picture
Anonymous says:

why do sounds change pitch as they move and can this change in sound be controlled???

posted on Tue, 03/17/2009 - 4:30pm
Tim Kaiser's picture
Tim Kaiser says:

A specific sound doesn't necessarily change pitch as it moves, but our perception of it can. The Dopler effect is probably the best example of this. Sound waves that move past you (standing by the tracks when a fast-moving train goes by, for example) are being perceived by your ears differently than when a sound is fixed. We can change the pitch of lots of sounds that we generate, too. Playing musical instruments is all about controlling pitch.

posted on Sat, 03/21/2009 - 11:06am
Anonymous's picture
Anonymous says:

What is the best way for an aspiring super-villian to utilize sound as a doomsday weapon?
uh... for research purposes only, of course.

posted on Wed, 03/18/2009 - 4:24pm
Tim Kaiser's picture
Tim Kaiser says:

There have been a number experiments done (mostly by the military) to see if sound could be used as a weapon. Super low frequency sounds at very high volume levels can actually incapacitate a person. I won't go into the gory details, but suffice it to say that your mother was right about the clean underwear thing. The real trick is to have so much amplitude that you FEEL the sound more than you hear it. Good luck in your world domination endeavors!

posted on Sat, 03/21/2009 - 11:10am
Anonymous's picture
Anonymous says:

Tim how does the ear receive sound and know what we hear ?

posted on Sat, 03/21/2009 - 11:51am
Tim Kaiser's picture
Tim Kaiser says:

Your ear "hears" when sound waves go into the ear canal and transmit their vibration to your eardrum and the bones deep inside. Nerves transmit this to your brain which interprets the sound. If you don't have a brain, you can't hear!

posted on Sun, 03/22/2009 - 10:33am
Anonymous's picture
Anonymous says:

what is your favorite musical instrument sound?

posted on Thu, 03/26/2009 - 10:16am
Tim Kaiser's picture
Tim Kaiser says:

I like a lot of different things, so it's kind of hard to pick just one. That said, it's a toss-up between the bass clarinet and the theremin.

posted on Thu, 03/26/2009 - 11:12am
From the Museum Floor's picture

Why are some decibel levels negative?

posted on Thu, 04/02/2009 - 3:23pm
Tim Kaiser's picture
Tim Kaiser says:

Decibels, the unit used to measure sound levels, are in fact a ratio between the sound you want to measure and a reference level. Reference level depends on the situation, so a negative decibel measurement is in proportion to the reference level.

posted on Thu, 04/02/2009 - 4:55pm
From the Museum Floor's picture

Why do really low sounds make things shake?

posted on Thu, 04/02/2009 - 3:24pm
Tim Kaiser's picture
Tim Kaiser says:

All sounds require a medium- in our everyday world, it's air. Sound waves travel through the air and make the air move along with it. Really low sounds (at high amplitude) move a lot of air, which in turn can move objects, particularly those that aren't nailed down! Big loud speakers actually have a "port" which is an opening to allow the air to move with more force without destroying the speaker enclosure. High frequency sounds can also shake things if they resonate sympathetically. Ella Fitzgerald can sing a note capable of breaking a fine crystal glass if it resonates at the same (sympathetic) pitch.

posted on Thu, 04/02/2009 - 5:01pm
Zoie115's picture
Zoie115 says:

how fast does sound travel and what (if any) is the name of a device that can pick up sound waves?

posted on Fri, 04/03/2009 - 2:53pm
Tim Kaiser's picture
Tim Kaiser says:

In dry air at 20 °C (68 °F), the speed of sound is 343 meters per second (1,125 ft/s). This equates to 1,236 kilometers per hour (768 mph) or about one mile in five seconds. In aeronautics, the speed of sound is called Mach, so 768 mph is Mach I, 1536 mph is Mach II, etc. Any kind of microphone can pick up sound waves, but to measure them, you need a sound pressure meter. Radio Shack sells them and they are surprisingly accurate.

posted on Sun, 04/05/2009 - 12:11am
Anonymous's picture
Anonymous says:

Do you believe that in the future we will be able to use sound to produce energy? ie, transportation, heating and cooling etc.

posted on Wed, 04/08/2009 - 1:27pm
Tim Kaiser's picture
Tim Kaiser says:

I'm not sure that the physics are there to capture meaningful energy from sound. It takes too much energy to generate the sound on the front end to get more out of it on the other. There are more likely to be efficiencies gained by manipulating by-product sound in existing processes- e.g. reducing, damping or harmonically modifying mechanical noise in a machine to make it work better. I'm sure there are some good sci-fi potentials for an ultrasonic beam generator, though!

posted on Thu, 04/09/2009 - 12:29pm