3. Sound pitch demystified

You mean there is some serious technical stuff to learn in these tutorials? I want my Mozart!

1. Topics of discussion

In this tutorial, we will be taking a look at some aspects which relate to sound theory rather than music theory, but are useful in understanding how sounds are perceived by the human ear. So, let’s have some fun.

2. The technical aspects of sounds

So in the previous tutorial I mentioned that you can distinguish two sounds because their pitch is different. Now I may have used the same note in two different octaves as an example, but this holds true for two different notes (e.g. C and D) as well. They sound different because their pitch is different.

But before we talk about pitches, let’s first take a look a graphical representation of a song. Each sound can be represented as a sine wave. Here is a representation of an A note (A4, with a frequency of 440 Hz, to be exact):

sine

As you can see, the visual representation is a sine wave which has various places where it either hits a maximum value, 0, or a minimum value. And as you can see, I’ve labeled an area as a wave cycle. Basically, a wave cycle begins at the place where a sine wave hits 0 and then continues its ascending towards the maximum value and ends in the place where the wave once again hits 0 after rising from the minimum value.

Why are wave cycles important you ask? Well, the number of complete wave cycles a sine wave makes in a second gives us the frequency of that wave. And frequency is the measuring unit which helps us quantify a sound pitch. Frequencies are measured in Hertz (Hz).

So what is this pitch we speak of? Well, a complex definition would be something along the lines of “it is a subjective attribute of a sound, which allows us to differentiate between different sounds”. The simpler definition refers to how high we perceive the sound. The higher we perceive the sound, the higher the pitch associated to the sound is and consequently the higher the frequency.

The concept of frequency is also important because of a certain term called octave. Last time I told you that when learning a scale, we usually start with a note and end with the same note but an octave higher.

Basically, an octave refers to the musical interval between a certain note and another one which has a frequency either halved or doubled. This is why the perceived sound is the same, only lower or higher. Last time I also told you that you may encounter notes labeled something like C4, with 4 being the octave in which that C note is located. This particular C note is also knows as middle C, because on a piano it’s the note located at the exact center of the piano keyboard.

So how many octaves are there you ask? And how does sound perception relate to frequency? Well, the human ear is usually capable of perceiving sounds with frequencies between 20 Hz and 20 kHz (some can even hear sounds with frequencies lower than 20 Hz) and in this frequency interval we have a total of 10 musical octaves. You can take a look at this table if you want to see the frequencies for octaves 0 to 8. Yeah, there’s an octave 0, presumably because C0 has a frequency lower than 20 Hz, though I would recommend to not quote me on that.

Some of you may be wondering why this is important. And the answer can be boiled down to harmony. These notes have the frequencies and pitches that they have because they are the values researchers have come to realize are the ones that provide the best experience to the human ear. And no, you don’t have to memorize these values, nor use them when tuning your instrument. There are professional tools and people for such a matter should you not know what you are doing.

That about wraps it up for this tutorial. Next up, we’re gonna take a look at musical sheets and start reading some music. See you then.

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