Physics of sound
This text is optional. Especially for those people who are not going to seriously work with sound, but want only in their free time to play the synthesizer and make some music for their pleasure. In principle, you can quite easily use a computer for musical purposes without knowing the basics of acoustics, electrical engineering and other applied disciplines.
But if you are a professional musician or an “advanced” amateur, then everything that is written below, you just need to know. Without this, you will not be able to get a conscious result, and in the future to creatively use programs avoiding template solutions. And this requires at least an understanding of the basic laws of acoustics. Therefore, gather your thoughts and start reading – we tried to make your task as easy as possible and, as much as possible, simplified the story.
By the way, many Western musicians do not particularly bother to study equipment or, especially, some suspicious fundamentals of physics, and rely entirely on technicians, sound engineers and producers. When they come to our country, they are genuinely surprised to see how, when preparing a concert, the guitarist is busy with tuning many amplifiers and tells the sound engineer how to adjust the sound. Or in general, takes a soldering iron and begins to conjure over connecting cords. In the West, this is not accepted. Every person in them does his own thing and tries to do it as well as possible. Therefore, there is such an exotic profession for us as a sound producer who is responsible for setting the sound of the project and not only selects instruments and “lotions”, but also changes the musicians if the latter do not fit into the intended sound.
In our country, everything is arranged differently – the musician is left to his own devices. Therefore, he has to be a jack of all trades in order to at least get the opportunity to properly compose music or record his original material. We all have to understand the arrangement of instruments, studio and concert equipment, computers and many other things that our Western colleagues do not know and do not want to know.
This book should help you get hold of music applications for your computer. If you are an amateur, you can at your pleasure try your hand at composing music, arranging it or just learning to play. If you are a professional, then after mastering the techniques and programs you can record albums at home and release CDs yourself. If you seriously want to realize your creative potential, then today the only possible option for existence is to be not only a good musician, but also a good technical specialist.
In this chapter you will learn what sound is, what its nature is, and how it is recorded …
What is sound?
Any person who has studied (or is studying) at school, without much thought, will answer this question like this: “Sound is a wave.” And he will be absolutely right. But when trying to explain what this wave is, most people recall a textbook example with a rope or waves on the surface of the water and then think for a long time. So what is sound?
Any object making reciprocating movements (tuning fork, piano or guitar string, our vocal cords, etc.) causes an alternating decrease or increase in density in the air. The movements of some air molecules are transmitted to other molecules, as a result of which periodically repeating zones of increasing and decreasing density propagate in space. They are a sound wave (Fig. 1.1.). If we put in some place a device capable of responding to changes in the density of air, write down its readings for some time and make a graph of the dependence of density on time, we get a curve close to a sinusoid, familiar to us from school physics textbooks (Fig. 1.2 .). It is such vibrations that are caught by our ear, as a result of which we get a sense of sound.
The number of air vibrations per second is called the frequency of sound. Waves with different frequencies are perceived by us as sound of different heights: waves with a low frequency are perceived as low, bass sounds, and waves with a high frequency are perceived as high. Frequency is measured in Hertz (Hz): 1 Hz = 1 oscillation per second; or kilohertz (kHz): 1kHz = 1000 Hz. Most people from 18 to 25 years old are really capable of hearing air vibrations with a frequency of 20 to 20,000 Hertz (with age, the upper limit of perception decreases). It is this range of waves that is called the sound range.
The frequency of the wave is inversely proportional to the wavelength – the segment on the axis of wave propagation, which fits the complete cycle of changes in air density. The higher the sound frequency, the shorter the wavelength and vice versa. The wavelength is very easy to calculate by the formula l = C / f, where C is the speed of sound (340 m / s), and f is the frequency of sound vibrations. For example, a wave having a frequency of 100 Hz has a length of 340/100 = 3.4 m.