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What is Macrosonic ?

Elastic waves Consider a volume V which is home to a continuous medium, is essoun gas, liquid or solid at rest. There are various sizes and properties of the medium, such as temperature, pressure, density, which may have different values diversipunti the medium.

Suppose that, while varying from point to point, these values remain unchanged over time. Now, if somehow we introduce unaperturbazione pressure and density (or both, for example in gas these two quantities are related, thus varying the other one was also varies), if the medium has a certain elasticity, disturbance propagates in the middle.

In other words, the pressure (and / or density), as well as vary dapunto up, will also change over time. A disturbance that propagates in half due to the elasticity of the same elastic wave is called. The sound A vibrating body immersed in it in the air produces the ondeelastiche giving rise to the phenomenon that is called sound. For this elastic waves are called acoustic waves or sound waves. The acoustics is part of physics that studies the acoustic waves.

The easiest way to produce a sound is to place a vibrating body, such as, for example, the string of a guitar or a membrane of a drum. We begin the study of sounds with the sounds simple. Consider a cylindrical tube surrounded by air, with a free end, while the other is inserted a piston that vibrates with sinusoidal motion, ie, if x (t) indicates the depth of the piston inside the cylinder at t, we have where indicates the frequency of vibration of the piston.

This, in its motion, compresses the air around the cylinder piston that increases its density, and when the piston goes back on it produces rarefaction, ie, the density decreases, due to the elasticity of air changes densities will propagate into the cylinder as a sine wave having the same frequency of vibration that produces it. The propagation speed depends on the medium and its temperatura.Nel our case, where the medium is air, the speed is 331.4 meters per second at 0 degrees ° C. The following table gives the values of the speed of sound in varimezzi. What we have just seen is an example of a simple sound. A sound that is simple if sinusoidal. Let us now examine the characteristics of a simple sound.

Height of a sound

We have already spoken of frequently. It is defined as the number of oscillations per unit time at a fixed point. If as a unit of measuring time using the second, then the frequency is measured in Hz The average human ear can hear sounds that have a frequency of 16 Hz and 20,000 sounds high or acute, are those whose frequency is close to 16,000 Hz, low ones are frequently closer to 16 Hz When we speak of 'height of a sound, it refers precisely to the frequency of an audible sound. Infrasound is sound with a frequency below 16 Hz, the frequency of those with more than 20,000; ultrasound and infrasound are both above the threshold dell'udibilità.

Wavelength As each wave, the period of a simple sound is the time it takes to make a full swing.

Of course, the period is simply the inverse of the frequency The wave propagates in time can be described as a density wave, or better than the density variation of density media. The law of such a wave will where is the wavelength. If we let the propagation speed of sound in air will Sound intensity The intensity of sound at a point P is the amount of sound energy through a unit surface area located at the point P perpendicular to the direction of propagation of sound. Of course, a sound will be more energetic than the greater the density difference caused by it, that is elegance at its' size.

Commonly, an intense sound that a loud sound, a sound that has pocointenso weak sound. In the example of pipe that we considered, the intensity does not change along the tube. In general, however, the intensity decreases away from the source, what happens when the sound can spread in the space surrounding the source, so that the energy transmitted through the sound it must be distributed over an area increasing as one moves away from Source.

Stamp

So far we have considered simple sounds, ie those whose waveform is sinusoidal. In fact, the profile of a sound wave can take diverseforme. The character of the sound depends on the wave form is called timbre. Thus, sounds with the same frequency and same intensity may appear different because they have different timbre.