SamplecrazeStretch That Note

Synthesis - Part 1

Understanding Sound

To understand any part of synthesis you need to understand sound, what it is, how it moves, how we perceive it and why we perceive it the way we do. Once you understand this then shaping it or manipulating it becomes so much easier.

Sound is the displacement of air around the source and how we perceive that displacement. Right, what does that mean? Think of the best and most commonly used analogy: that of dropping a stone in a pond and watching the ripples form. The ripples always move away from where the stone meets the water (source). The air displacement is the ripples created by the dropping stone. In this case we see the ripples. In the case of sound we hear the ripples (the displaced air). How do we hear the displaced air? Our eardrums pick up the displaced air and our brains then process the data as sound.

Fig1 SOUND WAVES

 

Now let us look at the components that make up sound. There are three and really quite simple to understand if you apply the ripple analogy. The displacement of air or air pressure as is more commonly known creates the waves in fig 1 and is know as Sound Waves. The rate at which these waves occur is called Frequency.

So our first component of sound is Frequency.

1. FREQUENCY

This is simply calculated at how many cycles (waves) occur every second. These cycles are repeated so really we only need to look at how many cycles (waves) occur in one second. The result is measured as cycles/second and this unit of frequency is called a Hertz and the abbreviation is Hz. You cannot get simpler than that...how many cycles hit you in one second. Heinrich Hertz was a dude who worked with wavelengths and frequency, so we have to thank the man and it seemed only right to name this little calculation after him.

To give you an example of how easy this is check out the following:

If you had 50 cycles hit you in one sec then that would be a 50Hz wave. There, simple and makes you look cool in the bar when you want to impress someone.or maybe not.

So it also follows and makes complete sense that if you had 10,000 cycles per second then that would be 10,000 Hz, but, because we don't want to have to write so many numbers every time a thousand appears we use the k letter to mean a thousand. So, 10,000 Hz is now written as 10 kHz. There is a reason we do this and it's not because we want to look deep and complicated individuals but simply because of all the work that has been carried out on our hearing range in the past. And a range was formed, sure it varies but generally speaking, our hearing range is anywhere from 20 Hz, deep, to 20 kHz, high.

So we now know that higher frequency sounds are higher in pitch as there are more cycles per second and lower frequency sounds have fewer cycles per second.

Right now I think it is important to show you a Mid to frequency chart for all the notes on a keyboard or scale and the midi note numbers as well as this will come into play at a later date when we deal with synthesis and programming with the use of midi.
You do not need to learn this chart in parrot fashion but it is important to understand some of the frequencies that are used as, later, you will need to know these frequencies so that if you need to use equalisation or filters to shape a sound or remove or add certain frequencies, then the chart can prove to be invaluable.

In most cases, you only need to recognise the main frequencies for certain notes. For example: C4 at 261.63 Hz is a great reference point, because then you can find, easily, C5 or C3 etc..
I cannot stress how important frequencies are for the understanding of sound and synthesis. Engineers live by them as do producers and Sound Font developers.

If there is one piece of information that overrides any other in terms of importance it is the understanding of frequencies. How often have you tried to mix your track only to be mystified by the result? Terms like 'muddy' or 'thin' spring to mind and these are all because the mixer or producer does not have an understanding of frequencies and their effect on other frequencies in a mix. Understand this basic concept and you will be armed with the most potent weapon. The rest of synthesis is the understanding of how to shape these frequencies to create new ones or to bring out the best in a spectrum of sound.

The Chart 

Midi No  Note  Keyboard  Freq  

N       Midi Note    Frequency              N       Midi Note    Frequency

Name Midi Note Frequency Name Midi Note Frequency Name Midi Note Frequency
 A0      21    27.500  C3      48   130.813  D#5      75   622.253
 A#0      22    29.135  C#3      49     138.591  E5      76   659.255
 B0      23    30.868  D3      50   146.832  F5      77   698.456
 C1      24    32.703  D#3      51   155.563  F#5      78   739.989
 C#1      25    34.648  E3      52   164.812  G5      79   783.991
 D1      26    36.708  F3      53   174.614  G#5      80   830.609
 Eb1      27    38.891  F#3      54   184.998  A5      81   880.000
 E1      28    41.203  G3      55   195.997  A#5      82   932.328
 F1      29    43.654  G#3      56   207.652  B5      83   987.767
 F#1      30    46.249  A3      57   220.000  C6      84  1046.502
 G1      31    48.999  A#3      58   233.082  C#6      85  1108.730
 G#1      32    51.913  B3      59   246.942  D6      86  1174.659
 A1      33    55.000  C4      60   261.623  D#6      87  1244.507
 A#1      34    58.270  C#4      61   277.183  E6      88  1318.510
 B1      35    61.735  DE4      62   293.664  F6      89  1396.913
 C2      36    65.406  D#4      63   311.127  F#6      90  1479.978
 C#2      37    69.296  E4      64   329.628  G6      91  1567.982
 D2      38    73.416  F4      65   349.228  G#6      92  1661.219
 D#2      39    77.782  F#4      66   369.994  A6      93  1760.000
 E2      40    82.406  G4      67   391.995  A#6      94  1864.655
 F2      41    87.307  G#4      68   415.305  B6      95  1975.533
 F#2      42    92.499  A4      69   440.000  C7      96  2093.004
 G2      43    97.999  A#4      70   466.164  C#7      97  2217.461
 G#2      44   103.826  B4      71   493.883  D7      98  2349.318
 A2      45   110.000  C5      72   523.251  D#7      99  2489.016
 A#2      46   116.541  C#5      73   554.365  E7     100  2637.020
 B2      47   123.471  D5      74   587.330  F7     101  2793.826

As you can see from the chart above that for every octave you go up you double the frequency and it is the same in reverse, for every octave that you go down, you halve the frequency. The relationships between pitch and frequency are clearly evident in the chart.

Example: C4 is 261.63 Hz. To get to C5 we double the frequency so it is now 523.25 Hz. And if we wanted to go from C4 to C3, it would be 130.81 Hz.

I always imagine a wave as a 3 dimensional entity and with that I attach colours and size. So, for a low frequency wave I will think of it as a large and flowing wave with nice warm colours like orange or deep red and the whole image is nice and slow. For higher frequencies I use smaller and faster waves and in harder colours like bright yellow or striking blue. This image is then enhanced further by having a person standing in front of the waves, usually me, but my name is Hertz and I am listening to these waves in a rent a car. Although this may now confirm the urgency for me to seek therapeutic help, it is the best way for me to remember things. You can create whatever images or story lines to the definitions in this tutorial. They are your images and must work for you.

2. AMPLITUDE

Generally speaking this means the loudness or level of a sound or waveform . I prefer the word waveform for sound as it is the form or shape that the waves take and the further we go into this tutorial the more that term will make sense as waveforms vary in shape and character so, from now on, I want you to use the word waveform for sound. It is better defined with a simple graph. In fact, now is as good a time as any to introduce you to graphs. Enter fig2.

Fig2

 

As you can see, the waveform, it's actually a sine wave but don't worry about that for now as that is the next subject we will cover, is 2 cycles and I have arrowed in the second cycle, no difference which cycle I arrow as they are both repeats, anyway I had to arrow the second cycle so as not to intrude on the amplitude line in the first cycle. The height or peak of the waveform is the amplitude and the length is measured as 2 cycles and this is done very simply. Imagine a sound and how it starts. It starts from 0 then goes up (+1), hangs about and then drops off. In the diagram you can see the waveform starts at zero, goes up, drops to zero then goes to the negative area (-1) and then climbs to zero again. This is using the wave theory we defined earlier and all waveforms are represented like this, as a graph, and how each cycle behaves or how a number of cycles behave in relation to each other. For now you do not need to worry about complex waveforms and any other factors regarding waveforms as we will deal with them as we go along, at your pace, that way you do not feel as if there is too much information to learn. This is meant to be fun so let's keep it that way. Later we will look at wavelengths, decibels, phase etc.. so for now we need to look at the most basic waveforms that are found on synthesizers , what they are, how to draw them graphically and what type of sound each waveform produces. This leads onto the next subject: WAVEFORMS

WAVEFORMS

The final most important component of sound is TIMBRE. This is what defines the tonal quality of a sound. A C4 note played on a piano and at the same level as a C4 note played on a saxophone does not produce the same sound or timbre. They are both the same level and both played at C4 but both have distinctly different sounds or timbres. Timbres are made up of waveforms and it is these waveforms that go to make up the tonal quality of a sound. This is called timbre.
Although there are countless waveforms and some are very complicated in nature, there are certain standard waveforms that are always seen on analogue synthesizers or any modern day synthesizers, be it hardware or software, that have synthesis capabilities.

They are as follows and are shown graphically and you can even listen (audition) to them so you can familiarize yourself to the way they sound.

Saw at C4 (Right Click 'Save Target')

Sine at C4 (Right Click 'Save Target')

Square at C4 (Right Click 'Save Target')

Triangle at C4 (Right Click 'Save Target')

Noise (Right Click 'Save Target')

These waveforms have their own sonic (sound) qualities and if you have a basic understanding of what they sound like and what they are usually used for then you are half way there to understanding how to manipulate them.

Sine waveforms are great for creating deep warm basses or smooth lead lines. They can be used to create whistles, layered with kick drums to give that deep subby effect. In fact the sine wave is a pure waveform and it does not possess any harmonis.. That means that almost all other waveforms are created from sine waves at varying frequencies and amplitudes.

The sine is a nice smooth flowing waveform.

Saw waveform, or sawtooths as they are more commonly known, have a rich and bright, edgy sonic quality about them and are great for creating strings, brass, huge Trance pads, searing leads and electro basses. Of course there is, as with all the other waveforms, far more to it than that, but, as I said, I just want you to get a general idea of what these waveforms are used for and how they sound. The real fun starts when we start to layer them or trigger one with the other, but that will come later when we get into synthesis.

Triangle waveforms are great for bell type sounds or wind type sounds like flutes etc.and I regularly use them for the FM type of sounds that you hear on Yamaha DX7s or FM7s, great and very useful.

These waveforms look like triangles so that makes life easier.

Square waveforms are great for brass and deeper wind type of instruments and are usually used along with other waveforms as they are quite strong and hard on their own. But they are invaluable as are the rest listed above.

As you can see the square waveforms look like a bunch of squares with their tops and bottoms missing and alternatively.

Noise waveforms are used more for effect than anything else but I find that they are fantastic for creating pads along with other waveforms like saws and triangles. You can also create great sea shore wave type of sounds or huge thunder or even some great Hoover type sounds when used with saws. Endless what you can do with these waveforms and for that reason alone you see that most synthesizers, software or hardware, have these waveforms as the main sound source. The rest is all about the actual synthesis or programming of these waveforms.

These are the easiest ones to remember, a mesh of what seems like radio static or just rubbish.

SO, there you have it:  A simple and basic explanation of sound and waveforms, what their characteristics are, how we perceive them, what they are used for and best of all ' the tagging method '.

Next  we will look at the different types of synthesis, a slightly more in depth look at waveforms, what is ADSR and how we use it to shape a sound, what are the components of synthesis and definitions for all the terminology and components in synthesis along with a bunch of some very cool looking graphs.