We explain what acoustics is, what its branches are and what acoustic phenomena it studies. Also, what is noise pollution.
What is acoustics?
acoustics is the branch of physics what he studies sound. Is a natural Science dedicated to understanding the phenomena of production, transmission, control and reception of sound, infrasound and ultrasound, as well as their effects in the real world.
Acoustics defines sound as a vibration, that is, the mechanical propagation of waves through the matter, be in solid, liquid or gaseous state, and tries to describe this displacement through formulas and mathematical principles.
It is one of the sciences oldest of humanity, whose beginnings can be traced back to Classical Antiquity, between the 6th century BC. C. and I d. C., especially in Greece and Rome. His first formal studies, carried out by Pythagoras (ca. 569-475 BC), had to do with the understanding of musical sounds, to try to understand why some sounds are more beautiful than others.
It was Aristotle (384-322 BC), more than a century later, who discovered that sound is composed of contractions and expansions of air, and the first treatise on the matter was written centuries later by the Roman architect Vitruvius (80- 15 BC), around 20 BC. c.
However, it was from Scientific revolution of the Renaissance that the laws that govern sound began to be discovered, thanks to the studies of vibrating strings by Galileo Galilei (1564-1642) and Marin Mersenne (1588-1648).Isaac Newton (1642-1727) would later join them and later the so-called "giants" of acoustics: the German Hermann Helmholtz (1821-1894) and Lord Rayleigh (1842-1919), among other great scientists studying sound.
The first attempts to measure the speed of sound in air, one of the founding achievements of acoustics, were made in the 17th century and, although they were not very exact, they revealed that the speed of waves does not depend on their frequency. In 1738 the Paris Academy of Sciences achieved a measurement almost equal to the value currently handled: 331.29 meters per second.
Today, acoustics is an important discipline with numerous technical applications, both in the field of architecture and urban planning, as in medicine, Arts and entertainment, and telecommunications, and even in the military world (like the radar mechanism).
branches of acoustics
Acoustics encompasses a varied set of sub disciplines or specializations, among which the following stand out:
- Architectural acoustics. Branch of acoustics dedicated to the study of the movement of sound in buildings and urban spaces, in order to build them in such a way as to take advantage of the nature of sound.
- music acoustics. Branch of acoustics dedicated to the study of sound in the artistic context, that is, of music and of the sounds considered beautiful. It deals with both musical instruments and scale tuning systems.
- physiological acoustics. Branch of acoustics dedicated to the study of the functioning of the auditory apparatus, its diseases, disorders and other implications.
- Electroacoustics. Branch of acoustics dedicated to the study of the capture, reproduction, amplification and production of sound through electronic devices such as microphones or speakers.
- underwater acoustics.Branch of acoustics devoted to the study of sound when it is produced and transmitted underwater.
- Psychoacoustics. Branch of acoustics dedicated to the study of the relationship between sound and the human mind, that is, the way in which we react to Humans to the sound
- Bioacoustics. Branch of acoustics dedicated to the study of sound in living beings, especially animals: the function of the sounds they emit, the disposition of the speech apparatus, among others.
- Industrial acoustics. Branch of acoustics dedicated to the study of the sound generated by human productive activities, the forms of noise pollution and the impact of sound in the work environment.
acoustic phenomena
Sound propagates in the physical environment in the form of mechanical waves, whose properties allow them to undergo different alterations and transformations, known as acoustic phenomena. The main phenomena are:
- The reflection. It is a phenomenon that occurs when sound waves meet a physical object that alters or modifies its original trajectory, which produces a rebound effect that can send it back to its original source. Depending on the conditions in which the reflection occurs, other similar phenomena may occur, such as:
- the echo It is a type of sound reflection in which the wave returns to its emitter after hitting a reflective surface, in cycles with an interval close to 0.1 seconds. It is similar to the effect produced by light when impacting the mirror, returning part of its own sounds to the emitter, as in the long caves in which we can hear our voice repeated towards us.
- The reverb. It is a phenomenon associated with the reflection of sound, in which a sound can be heard time after it has stopped emitting, that is, when its emitter is silent.This phenomenon is also due to acoustic persistence, and is interpreted as a lengthening of the initial sounds, as in the case of the noise that accompanies an explosion.
- standing waves. It is a phenomenon that occurs when a reflected wave is added to the original wave on the same axis, which modifies the properties of both and increases or decreases its amplitude, so that the resulting sound is very different from the one emitted. This is what happens when a microphone records the output to a speaker of its own sound, that is, when the feedback.
- absorption. It is a phenomenon that can be considered as the opposite of reflection, since in this case the sound waves, when encountering a physical barrier, do not alter their course, but are canceled or neutralized, either partially or totally. This phenomenon is used to soundproof certain spaces, such as places of musical practice, preventing the waves from propagating further, towards the outside.
- The refraction. It is a phenomenon that occurs when sound waves propagate from one physical medium to a different one (for example, from air to water or vice versa), and in the process their speed and direction are modified, to a degree equivalent to the physical properties of the environment to which they move. We can experience this phenomenon if we dive into a pool and listen to those who speak on the surface.
- diffraction. It is a phenomenon that occurs when sound waves encounter an obstacle in their path, surround it and turn the surface of the obstacle into a source of secondary waves (diffracted waves), which causes the sound to disperse in the environment. It can also occur when sound waves pass through a small opening and spread out into the new environment, such as when we speak through a tube and our voice emerges distorted from the other side.
- The interference.It is a phenomenon that occurs due to the superposition of two harmonic sound waves, which modify their properties in the process. When this overlap causes a gain in amplitude, it is called constructive interference; when instead amplitude is lost, we speak of destructive interference. This is what happens when we are in an environment full of people talking and it becomes difficult to hear the person next to us.
- The doppler effect. It is a phenomenon that occurs when the emitter of the waves moves quickly with respect to the receiver, either moving away or approaching, and this movement affects the frequency of the sound waves. It is what happens when an ambulance passes by us and its characteristic sound gains frequency when it approaches and loses it when it moves away.
noise pollution
Noise pollution is the continuous emission of intrusive sounds in an environment or ecosystem, which produce noise and prevent or hinder the propagation of natural sounds typical of said environment. Noise pollution is very noticeable in the cities, where the accumulation of sounds can become intolerable and even physically harmful to the body, while in rural and wild areas there is a lower incidence of annoying sound waves.
This type of contamination has effects on Flora and fauna of the habitats, and especially in the psychic stability of people, since it can induce them to states of agitation, unpleasantness, anguish or distraction.