The sound is the main part of music, because without  it, simply music wouldn't exist. 

That is why it's study is vital for the understanding of music. An extense explanation if presented next, but if you want to understand it better, we suggest that you see the adventures of Mr. Note in the Main Page

Sound

      The phenomenon of the sound is related to the vibration of the material bodies. Whenever we listened to a sound, there is a material body that vibrates and produces east phenomenon. For example, when a person speaks, the sound whom it emits is produced by the vibrations of its vocal cords; when we touched a drum, a piece of wood or one of metal, these bodies vibrate and emit sounds; the cords of a piano or a violin also are sonorous when they are in vibration, etc.

      All these bodies are sound sources (or sonant), that when vibrating produce waves that propagate in the average material (solid, liquid or gaseous) located among them and our ear. When penetrating in the auditory device, these waves produce vibrations that cause the sonorous sensations.

    The sound propagates by means of waves, these sonorous waves provide our main form to us of communication (the language), and a favorite source of entertainment (music). But the sonorous waves also constitute an irritating distraction extremely (the noise). The sonorous waves become language, music or noise only when our ear perceives them like disturbances (in general in the air). The sonorous waves are longitudinal physically waves that propagate in solids, liquids and gases. Without means that allow this propagation, it cannot have sound.

This distinction between the sensorial and physical meaning of the sound gives a form to respond us to the old philosophical question: a tree falls in the forest and there is nobody hears it, was sound. The answers are no, in terms of the sensorial ear and if in terms of the physical waves, the answer depends on how the sound is defined. The definition of sonorous waves covers three aspects: the origin, the means of propagation (in the longitudinal sonorous waveform), and its detector, that must be the human ear.

In order to include/understand the sounds that the human ear catches we analyze the situation shown in the figure of the rule. This to the being put in vibration, causes in the air, successive compressions and refractions that propagate by this means, in similar form to which happens in means when it vibrates in lengthwise direction (as it were in the part of Waves).

If the rule vibrated to less than 20 times in a second (or 20 Hertz), or but fast that 20.000 times in a second (20.000 Hertz), the wave would not be perceived by the human ear since that is the rank of sounds that it perceives (of 20 to 20.000 Hertz).

 The infrasound and the ultrasound

A longitudinal wave that propagates in an average material with an inferior frequency 20 Hertz denominates infrasound, and if its frequency is superior to 20.000 Hertz, it receives the ultrasound name. As we saw, these waves do not cause auditory sensation some when it arrives at the ear of the people.

 But we know that some animals if they are able to perceive ultrasounds. Recent experiments demonstrate that a dog, for example, is able to perceive an ultrasound whose frequencies reach to 50.000 Hertz. To it it must that some trained dogs listen to the ultrasounds (produced by special whistles) that a person cannot perceive. Also one knows that the bats, even though are almost blind, can fly without hitting no obstacle, so that they emit ultrasounds that catch the ears after being reflected by these obstacles. The ultrasonic frequencies that the bat emits and hears later, can arrive until 120.000 Hertz.

 Sonic speed.

You already must have given account of which in a storm, even though the lightning and the thunderclap of a ray take place to the same moment, single we heard the boom after have seen the light of the flash. As it is of common knowledge, the light is the one who counts on the well-known fast speed but, that is approximately 300.000 km/s. and is due to this, that the lightning sees medical instructor the same moment at which it takes place. Then, the interval between the visual perception of the lightning and its auditory perception of the thunderclap, represents the time that the wave takes in arriving until us.

 Depending on the means in which one propagates, it will be the speed that the present sound. Next is a table in where they are these speeds in different means. 

Height of the sound

The height of a sound is the quality that allows us to classify it like serious or acute. Of general way, the men have serious voice (deep voice), and the women, acute voice (fine voice). In musical language one says that an acute sound is high and that one serious one is under (we observe that in daily language, the terms high and low. they are used sometimes in reference to the intensity of the sound, which must be avoided).

The height of the sounds is related to frequency f of the sonorous wave; so that at the most acute it is the sound, as much greater will be the frequency. Therefore, we can conclude that the frequency of the masculine voice, in general is minor who the frequency of the feminine voice (the vocal cords of the men vibrate with a frequency smaller than the vocal cords of the women).

The musical notes characterize by their height or frequency; that is to say, when a musical instrument emits different notes, it is emitting sounds of different frequency. In a piano, for example, to each key a sound different from frequency corresponds to him. The keys that are to the left of the pianist correspond to notes of low frequency (serious sounds), and those of the right they are the notes of high frequency (acute sounds).

 How does this apply in real life?

 The singers of classic music classify themselves in agreement with the frequency of the notes that are able to emit, and are the low ones (with serious, masculine voice), the tenors (with less serious, masculine voice, the sopranos (with acute, feminine voice, etc. The frequencies of the notes that these singers are able to emit vary from almost 100 Hertz (low) to 1.200 Hertz (sopranos).

Notes properties

 If we play a certain note of a piano, and if the same note (of the same frequency) were emitted with the same intensity by a violin, we could distinguish one of the other; that is to say, we could say clearly as note was the one that emitted the piano, and as the violin. We say then that these notes have a different timbre.

 This must to that the note emitted by the piano is the result of the vibration of not solely of the driven cord, but also of some other parts of the piano (air wood, column, other cords, etc.) which vibrate she along with. Therefore, the emitted note will have a form own, characteristic of the piano.

In the same way, the wave emitted by a violin, is the result of vibrations characteristic of this instrument, and for that reason it presents/displays a form different from the emitted one by the piano.

  We can express that:

 Our ear is able to distinguish two sounds of the same frequency and intensity, since the sonorous waves corresponding to them are different. We say that both sounds have different timbre.

What one says for the violin and the piano, is also applied to the other musical instruments: the resulting wave that each one of them emits, and who correspond to a determined note, has a form own, characteristic of the instrument; that is to say, each one of them produces its own timbre.  The voice of the people also has an own timbre, so that the form of the sonorous wave that produces is determined by personal characteristics. This it is the reason by which we can identify to a person by its voice.  

Good work, now you know, what sound it's all about!!!