Basics of audio

It is very important for us as recording engineers to understand the most basics of how sound works before we start making music at home

What is sound?

According to Wikipedia: 
"Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations"

In simple words, sound is any disturbance or vibration. Vibration is the key element of any sound that we hear.Vibration is the key to sound. Vibration is made up for small waves.

The following graph shows us a very simple basic waveform:

The vibration creates the waves 

As we study sound, we will focus on "number of waves in a sound" (hertz) and the intensity through which waves are travelling (volume). This will help us in crafting the sounds according to our need.

The vibration (or the sound) has two very basic elements:

  1. Velocity - is the intensity (volume) of the vibration
  2. Frequency- hertsz/ frequency (clarity) or what we think as pitch in the sound or the amount of vibration that occured in the source.

Note: -
Velocity, amplitude and volume means the same thing
Frequency is about number of waves or vibration per second.

1. Velocity
Is also known as volume or the intensity (pressure) through which the sound is coming. Think of a drum when the drum is hit by the stick the intensity is higher so it creates high volume sound.

When we shout, we put more energy and intensity that results into louder volumes.

2. Frequency

Frequency is measured in Hertz units. 1 Hertz is one cycle of sound wave per second. The more the number of cycles or the waves per second the higher the pitch or the clarity would there be.

Now the theoritical definition:
"Frequency is the number of wave cycles (measured in Hertz) in seconds. "
Let us understand hertz a bit more:

HERTz = cycles of waves per second in a sound
1 Hz = 1 cycle of wave per second
1 KHz = 1000 cycles per second
1 MHz = 1,000,000 cycles per second
1 GHz = 1 thousand million cycles per second

When we say that this sound is on 11 Khz this would mean that the waveform is completing around 11000 cycles in a second!

Human beings can listen to frequencies in the range of 10 Hz to 20 Khz. The higher limit decreases as we age. So a young teenager might be able to listen to sounds upto 20 Khz and a 50 year old man might listen upto 15 Khz only.

The mosquito ringtone!
Many college students put a mosquito ringtone. This ringtone is a sound with more than 18 Khz of frequency. While the students who are in their teens or tweens are able to hear the sound. While the teachers who are elder are not able to listen to it. This is a good example of how we listen to different sound frequency.

The ants
There are many other sounds in our surronding but we do not hear it. Small insects like ants respond to sounds lower than 10 Mhz of frequency while we may not notice the sound.

The waveform representing velocity and frequency

In the above diagram the wavelength represents one cycle of a sound i.e. Hertz. The more number of cycles or the hertz the higher the frequency is. The amplitude or the velocity is represented through Y axis.

Let us see a "real" wave diagram 

Newbies find the whole concept of wave and frequency a bit confusing.

I have tried my best to explain the concept in simplest possible manner. If you still don't understand i would suggest you to continue with the tutorial and come back and revise the stuff here.

Things will make more sense if you re-read the stuff in here.

In the meantime also have a look at the following video to see how a waveform looks:

Video explaining the concept of velocity & frequency 

In the following video i have tried showing you how a sound looks on the computer. It is represented by waves on the screen.

Let us do a quick revision of what we have learnt so far on this page

  • Sound is a vibration.... a disturbance in the air.
  • The intensity of vibration is the volume. The number of vibration is frequency (counted in hertz units).
  • Sound is made up of waves (these waves are similar to waves in water). The intensity of the sound is the volume(also called amplitude and velocity) and number of waves per second is the frequency (measured in Hertz unit). 

This was the most important section of recording tutorial. If you understand the stuff written in here you have almost become a recording engineer. 

If you have not, come back and read it again, i would appreciate if you ask me for any doubts or questions. I will update the info as i get feedback.

Because this is the most important part of our audio education:

The next chapter is dedicated only to revise the stuff that we have learnt here

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