Sound Basics

What is sound?” Good question.  

Sound is a form of energy. Energy is the ability to move something over a distance against a force. What is moving to make sound energy? Molecules. Molecules are vibrating back and forth at fairly high rates of speed, creating waves. Energy moves from place to place by waves. Sound energy moves by longitudinal waves (the waves that are like a slinky). The molecules vibrate back and forth, bumping into the molecules next to them, causing them to vibrate, and so on and so forth. All sounds come from vibrations.

Frequecies/Hertz

Those are both terms to describe vibrations. Frequency describes how fast something is vibrating. Hertz is a measurement of frequency and one Hertz is one vibration per second.

Our ears are our sound antennas. When something vibrates it causes energy to move by longitudinal waves, from the object vibrating to our ears. If that something is vibrating between about 20 Hz and 20,000 Hz it will cause your ear drum to vibrate. This is sound.

When something vibrates, it pushes particles. These pushed particles create a longitudinal wave. If the longitudinal wave has the right frequency and enough energy, your ear drum antennas will pick it up and your brain will turn the energy into what we call sound.

Let’s try a bunch of stuff with sound and vibrations to see if you can “catch the vibe.”


Experiment 1

Feel Those Good Vibrations

You Need:

A sound system

1. Turn on your music and turn it up fairly loud.

2. Take a look at your speaker. You should be able to see it vibrating. If there’s a song with a lot of bass, you should really be able to see it moving.

3. Put your hand on the speaker. Can you feel the vibrations?

4. If you want to, you can carefully put a bowl of water on top of your speaker. You should be able to see the water vibrate.

Remember that sound is nothing more than vibrating molecules. All speakers do is get molecules of air to vibrate, creating longitudinal waves. They push air. Your eardrums vibrate just like the speakers do when the longitudinal waves of sound energy hit your ears.


Experiment 2

To The Beat of your own Ear Drum

You need:

A sound system again

A balloon

1. Inflate the balloon. Get it fairly large.

2. Turn the music on loud (the more bass the better).

3. Put both hands lightly on the balloon.

4. Walk around the room holding the balloon lightly between your hands.

5. Try to feel the balloon vibrating.

6. Does the balloon vibrate more for low sounds or high sounds?

7. If you have a synthesizer (piano keyboard) you may want to try turning it up a bit and playing one note at a time. You should notice that the balloon vibrates more or less as you go up and down the musical scale. At very high notes, your balloon may not vibrate at all.

What’s causing the balloon to vibrate? Energy. Energy causes objects to move a distance against a force. The sound energy coming from the speakers is causing the balloon to vibrate. Your ear drums move in a very similar way to the balloon. Your ear drum is a very thin membrane (like the balloon) that is moved by the energy of the sound. Your ear drum, however, is even more sensitive to sounds than the balloon which is why you can hear sounds when the balloon is not vibrating. If you ear drum doesn’t vibrate, you don’t hear the sound.

Experiment 3

Ringing the Bells of Science

You need:

A mixing bowl (one of those metal bowls)

Something to hit it with ( a wooden spoon works well)

Water


1. Take the mixing bowl and put it on the table.

2. Smack it with the wooden spoon.

3. Listen to the sound.

4. Put your ear next to the bowl and try to hear how long the sound continues.

5. Now hit the bowl again.

6. Touch the bowl with your hand a second or two after you hit it. You should hear the sound stop. This is called dampening.

7. Now, for fun, fill the bowl with water up to an inch or so from the top.

8. Smack the bowl again and look very carefully at where the bowl touches the water.

9. When you first hit the bowl, you should see very small waves in the water.

I want you to notice two things here. Sound is vibration. When the bowl is vibrating, it’s making a sound. When you stop it from vibrating, it stops making sound. Any sound you ever hear, comes from something that is vibrating. It may have vibrated once, like a balloon popping. Or it may be vibrating consistently, like a guitar string or stereo.

The other thing I want you to notice is that you can actually see the vibrations. If you put water in the bowl, the tiny waves that are formed when you first hit the bowl are caused by the vibrating sides of the bowl. Those same vibrations are causing the sound that you hear.

Experiment 4

The Rubber Band Band

You need:

Shoe box or a mixing bowl

As many different sizes of rubber bands as you have (3-6 is good)


1. Stretch a few rubber bands around the box or the bowl. If possible, use different thicknesses of rubber bands.

2. Strum the rubber bands.

3. Feel free to adjust how stretched the bands are. The more stretched, the higher the note.

4. Try plucking a rubber band softly.

5. Now pluck it fairly hard. The hard pluck should be louder.


Again I’d like you to notice three things here. Just like the last experiment, you should see that the sound is coming from the vibration. As long as the rubber band vibrates, you hear a sound. If you stop the rubber band from vibrating, you will stop the sound. Sound is vibration. The audio signal is also "vibration". Energy = Vibration.

The second thing I’d like you to notice is that the rubber bands make different pitched sounds. The thinner the rubber band, or the tighter it’s stretched, the faster it vibrates. Another way to say “vibrating faster” is to say higher frequency. In sound, the higher the frequency of vibration, the higher the pitch of the note. The lower the frequency, the lower the pitch of the note. The average human ear can hear sound at as high a frequency as 20,000 Hz, and as low as 20 Hz. Pianos, guitars, violins and other instruments have strings of various sizes so that they can vibrate at different frequencies and make different pitched sounds. When you talk or sing, you change the tension of your vocal cords to make different pitches. (timbre)

One last thing to notice here, is what happened when you plucked the rubber band hard or softly. The rubber band made a louder noise the harder you plucked it right? Remember again that sound is energy. When you plucked that rubber band hard, you put more energy into it than when you plucked it softly. You gave energy (moved the band a distance against a force) to the rubber band. When you released the rubber band, it moved the air against a force which created sound energy. For sound, the more energy it has, the louder it is. Amplitude is the size of a wave. The more energy a wave has the bigger it is. When it comes to sound, the larger the wave (the more energy it has) the louder it is. So when you plucked the rubber band hard (gave it lots of energy), you made a louder sound. (amplified)

I said this in the beginning but I’ll repeat it here, hoping that now it makes more sense. When something vibrates, it pushes particles against a force (creates energy). These pushed particles create longitudinal waves. If the longitudinal waves have the right frequency and enough energy (loudness), your ear drum antennas will pick it up and your brain will translate the energy into what we call sound.

Sound is a form of energy.

Sound is molecules moving back and forth (vibrating) creating longitudinal waves.

All sound comes from something vibrating.

Frequency of sound waves determines the pitch.

Sound waves with a high frequency have high pitches. Sound waves with low frequencies have low pitches.

The human ear can hear sound energy as low as 20 Hz and as high as 20,000 Hz.

The more energy sound has, the larger the wave is (higher amplitude) and the louder it is.

We hear sound because vibrating particles vibrate our eardrums and our brain translates those vibrations into sound.


Questions


1. If sound is a form of energy, what’s moving?

2. All sound comes from what?

3. What kind of a wave is sound?

4. What does frequency have to do with sound?

5. What does amplitude have to do with sound?

6. What made the balloon vibrate when we played sound over the speakers?



Answers

1. Energy is the ability to move something against a force. In the case of sound, molecules are moving.

2. Vibrations. No vibration, no sound.

3. Longitudinal wave.

4. Frequency determines the pitch of the sound. The higher the frequency, the higher the pitch. The lower the frequency the lower the pitch.

5. The higher the amplitude of the wave, the louder the sound is. Higher amplitude means more energy which means louder sound.

6. Energy. Energy causes objects to move a distance against a force.

Hopefully this helps to get those good vibrations going.

What is energy?

Here's what wiki says.

http://en.wikipedia.org/wiki/Energy

What is Energy? Energy can simply be described as the capacity or ability to cause physical change. It is a requirement to achieving anything physically.

In the first post I talked about puting energy into motion, or creating it, but in the purist sense energy "IS", and is "ALWAYS". We think of things in starts and stops, but the reality of living on a moving planet dictates the "forms" of energy. To break it down very simply, we are talking about enegy in action, or energy in a holding pattern waiting the be put into action. Holding pattern as in capacitance (potential) vs action as in engaged values of actual and or transfer.

Hi Michael,

That is some good information given . I have got a question that I would like to ask on speaker placement.

Where is a good starting point to place and position your speakers in a room?
Is it in an area which has :

a) the most energy (highest pressure area) of the room ?

b) at a transitional point between most to least energy in the room ?

c) least pressured area of the room ?

I was reading about the pressure zone topic posted previously and it got me thinking logically I would want to position and place the speaker at an area which has the most pressure as it will excite and create more vibration which gives more volume(sound) and information but on the other hand it will create all sorts of different vibrations which may disrupt the total harmony and balance of the pressure zones or emphasise certain frequencies (guess that is where PZC's, RT's and SAM comes to the rescue).

Michael please your response .

Regards

Tj

Hi TJ

The scientific answer is: place your speaker in the position of oscillative balance.

In other words, once you figure out your room as an equalization tool, use it together with your speakers natural abilities, both good and bad.

For myself, I like to start with my ears in a place in the room (usually using the surface behind me) where the tonal balance is the most supportive of the flavor I want to listen to. I do the same with the speakers. Again in my case using free resonant speakers, I know that the speaker is going to mingle with the room, and I want to find the spot that has the best balance. My personal favorite way to start is with me against the back surface (extremely important to make that surface pleasant sounding). This rear surface I use as an extention of my ears ability to amplify pressure. The speakers placements depend on how I want to attack the soundstage. More times than not I will start my placement as far apart as they will go (usually inches from the side walls), then I will place them on one side of the center pressure zone or the other and see what side I like better to start with. I usually start with the speakers on my side of the zone than the far side.

Kinda like this



See the waves there? I play around with these finding the how far apart I can get those speakers.

In Fact, let me put in this whole thing to give visitors a peek.






Learning how your room works is the first step to getting great sound. There are three main components to acoustical waves in your room.

1) the individual sound wave
2) the laminar effect that the surfaces of your room creates along with any furniture
3) the pressure zones that build up in your room

the following is to help you see the room in action and how to bring the best out if it

first lets take a look at the laminar flow and pressure zone



All audio companies have a story to tell, but sometimes these stories are based on theory instead of practice. RoomTune is based on "live sound" research instead of "sound theory". The difference between these two approaches is one is looking at sound from what it might be and the other from what it is.

Why is this important? Because every room in the world sounds unique unto itself. No two rooms in the world have ever tested exactly the same, and in our research this is very key, because we design products that give acoustical solutions around the globe, and to all acoustical environments.

It's a must for us as an industry to apply true physics instead of bad engineering.



How did the audio engineering world get mixed up and start thinking that soundwaves are straight lines? What's worse is building a false science around something that should be pretty common sense. With RoomTuning we're going to get started on the right foot.

sound waves are spherical



Here is what a stereo sound source looks like in a room.



If my room is done properly, using the attributes of the pressure zones I should be able to stand almost anywhere in the room and get close to the same volume level, plus or minus the natural rise and fall of each pressure zone and along the laminar parimeters.

There is nothing in science that tells us that the following happens.



If a sound wave was 2 dimensional it would respond at the wall more like this.



What we have found in our testing is that there is an acoustical plane that developes on any surface where the on coming wave meets with the reflective wave. We call this the laminar line or laminar flow.



The next part we need to know about what affects the pressure zone is room loading.

Room loading happens when the sound waves meet at intersections such as the corners and midseams and the mid wall ceiling or floor.



Here's a 2D look at the loading and laminar flow together. Keep in mind the floor and ceiling are doing the same thing as the walls.



All rooms because they are enclosed build sound pressure. Here's a look if the speakers and chair were gone.



Your probably starting to get the picture of how powerful the room is and how big of a role it must play in the stereo's sound. It is without a doubt the biggest component.

A misconception is that the speakers play independent of the room, but lets think about this. How can a speaker play without the room? Air pressure is a function of the room not the speaker. The speaker is a vibrating source that sends the music signal into the air in the room but it's the room that amplifies this signal. A loudspeaker can not play louder or over power what the room is doing. You may think your listening directly to a loudspeaker but if this were the case the music would sound like it was coming directly from the speaker and there would be no stereo image to speak of. The sound would be very sterile as if someone cut away the music.

Take a look at the misguided view of the speaker minus the room if it were possible. Notice how much of the sound waves are cut out.



The only way to remove the room would be to hook a tube from the speaker to your ear cutting out the room altogether. Nope, far better to use the room, and why not? The room can be a wonderful tool that allows you to recover much of the content rather than trying to cut the acoustic information out.

This is why I named the product RoomTune and started the phrase "Roomtuning". We don't want to get rid of the biggest component but use it as the most important and final part of the audio chain. Once you accept this as the "music producer" you can view the hobby with more accuracy.

Let me show you my favorite way to listen and why.



Whether I chose to listen long or wide I find that using the room gives me, one a far bigger image (more real life size), and two a lot better tonal balance.

See the curved loading parts of the room? These are my pressure zones. Some of them depending on the types of walls you have and dimentions of the room plus what is in the room will vary the size and location but this is a fairly true placement guide.

I made the drawing simple but if you saw these they would actually look like spheres. Acoustical spheres hosting the sound of what ever the source is putting into the room.

Why are the speakers and my ears sitting right in the pressure zone? Because that's where the sound is at it's most developed stage in the rooms voicing. Those who chose to be in a weaker part of a pressure zone can but I find this is where most of the musics meat is. I also like to be inside the musics envelope so I put the speakers on my side of middle, catching a fair amount of the zones pressure if I can. If I however want to be in the extreme soundstage envelope I'll move the speakers closer or further away from the walls to pick up a nice boost.

You might try this and say this doesn't sound right. That's because we haven't started voicing the pressure zones themselves yet. There are three parts to voicing to keep it simple.

ears, speakers, pressure zones



here are the most obvious places to start treating your pressure zones

the pressure origins



Here you can change the sound of your room dramatically and it's not only about turning the volume of these pressure zone origins up or down but voicing them.
_______________________________

here's a look at an RT and RTD setup controlling the main on wall areas and main soundstage pressure zone



a view from your listening chair

The toughest part for a lot of folks is many of their rooms are listening/living rooms, so finding and shaping the pressure zones makes for challenges.

This is why when I set up my rooms, I take everything out and get the best sound possible with my room speakers and tools, then I start bringing the furniture back in and listen to if it is a help or not.

but let me show you a few past rooms









These 4 systems were all at the same location and I had to figure out how to incorporate them all together.