Technologies of the amplified musics - SpeedyLook encyclopedia

Initially, let us point out the concept of Musique: it is art to combine the sounds . Music being made up of its S, and the latter consisting of vibration S, the first tests of amplification come under the field of the Physique: undulatory movements, and in particular the Acoustic . Hi-fi: resulting from English " High Fidelity" (high fidelity) audio

Acoustics

the acoustic indicates the branch of the physics which studies the propagation of the sound.

By applying the theory of the waves to the sound vibrations, one already somewhat touches with a field control since the Antiquité.
to amplify a sound, one made use of the physical properties of materials in their giving a particular form. Thus constructions where were to occur Orateur S or Musicien S had very studied acoustics.
the apogee of acoustic amplification was the Renaissance with the construction of Cathédrale S and of room of Opéra S.

But the first forms of acoustic amplification were the first musical instruments.

Indeed, different the cases from resonance of the various instruments is studied to amplify the sound which comes, either of the cord S ( Harpe, Violon, Guitare, Piano, etc ), or of the ends for the wind instruments ( Flûte, Pipeau, trumpet, etc ).

That being also true for the instruments with percussion, and even for the human voice. Indeed, the human body acts as case of resonance for the voice.

Electric

Analogical

Electric handling of the sound is possible thanks to the electromagnetism.
Indeed a variation of the Magnetic field near an electric reel produces a Electric current Induit .

This makes it possible to collect the vibrations of the air using a membrane coupled to a reel which vibrates near a magnet; it is the principle of the dynamic Microphone . Thus the vibrations of the membrane generate a variable tension at the boundaries of the reel.
Inversement, if one applies a variable tension at the boundaries of a reel plunged in magnetic fields and interdependent of a membrane, one obtains a electrodynamic Haut-parleur .
However, the electrical signal produced by a microphone is too weak to be reproduced directly on a loudspeaker. It thus should be amplified.
This treatment of the sound is pressed on a chain Analogique because handling converts the sound, in electric current and conversely, while preserving the form of the Onde.

To praise qualities of reproduction of their apparatuses and to provide indicators of comparison, manufacturing them of electronic materials of treatment of reproduction of the sounds, into the Sixties introduced the concept of High fidelity or Hi-Fi for High Fidelity .

Amplifier

An amplifier takes in entry a signal of low amplitude and amplifies it on a useful level for the equipment which will be connected there at exit.

When the entry signal is very weak (a few millivolts, even less) one will use a preamplifier, whose role will be to relatively bring this tension to a level immune with the noise (a few volts). The exit of the preamplifier will be connected to the entry of the amplifier of power, which in its turn will be able to generate the current necessary to the power supply of the loudspeaker.

The first electronic amplifiers used the technology of the lamps, before evolving to the bipolar transistor. Today one always finds amplifiers with lamps, but the majority of the produced units use the transistor, bipolar or FET. One of the advantages of the transistors is their compactness which makes possible the realization of integrated circuits of power, where all the circuit of amplification is gathered in only one component.

One of the differences between technologies lamp/transistor is the possible production of Harmonique S odd by the transistors, returning the signal reproduces less pleasant with the ear than that reproduced by the lamps, where in fact the even harmonics will be produced. Nevertheless the field-effect transistors (FET) share this advantage with the lamps.

Numerical

In opposition to analogical, one speaks about Digital processing of the sound, when the treatments are accomplished on the result of the digitalization of the entry signal.

Sampling

One measures with regular interval the amplitude of the analogical signal: it is a sample.
Each second of the analogical signal is thus divided into sample S.
the precision of the Numérisation depends on the number of samples a second, but also of the number of values which can be taken by each sample.
the Théorème of sampling of Nyquist-Shannon forces to sample at least with the double of the maximum frequency contained in the entry signal. The value of the sample is coded on several bit S, for example, a coding on 16 bit S makes it possible to have 65.536 possible values. It is the coding used for the CD - Audio. The sampling rate is of 44,1 Khz, i.e. the sound is measured 44.100 times a second. In the industry of the sound production, the values can be higher, for example 96 Khz out of 24 bits.

Phonography

Among the sound activities most astonishing of the 20th century: the phonography .

To include/understand by this term the practice of the sound recording.
the hunters of sounds do not have of cease to find various apparatuses sensors and reproducers.

Typical instruments

In short, one has three types of instruments: sensors, transformers and restitueurs. In the modern musics, which easily use the amplified musics, one finds basic configurations.

Sensors

The sensors are called microphonous (in summary micro ). There exist Microphone S for the voice and of the adapted microphonous for instruments known as “acoustic”. The instruments called “electric” have integrated microphonous , and one can connect a cable directly on the instrument. Currently, technologies of transmission without wire by radio waves make it possible to limit the use of the cables.

Transformers

The principal transformer is the Amplificateur. This one restores the sound, with more or less of power, according to the adjustments. Often coupled with the amplifier, the Table of mixing makes it possible to manage several entries and exits of sound. Indeed it is on this table that one carries out the “balance” of a group: each level is regulated, and the sophisticated sound (acute, serious, sound effects).

Other machines, sometimes integrated into the table of mixing, or sometimes external, make it possible to add a special effect on a sound. Indeed, one will easily add Réverbération or dynamic Compression on a way. Some are in the form of pedal, making it possible to be actuated by the foot while playing. Among these effects, one can quote:

“the Octaver”: a sound with the octave
the “Wah-wah makes it possible to double”: allows to give to a sound an effect “close-open” (at the origin: Trumpet player S alternatively stop-emerging their instrument with a silencing device of jazz or more often - because less expensive - a debouchor of sink out of rubber)
the “Limiting device”: allows to crush the aural signal and in particular its peaks.
“saturations”: effects of Distortion, Fuzz and others: allow to saturate the signal before it arrives at the enclosures, which makes it possible not to damage them.
the “Flanger S”, “Tremor S”, “delay S”, “Chorus”…

Restitueurs

The Haut-parleur S transform an electrical signal into sound wave.

See too

External bonds

Kalerne
the handbook of the acousmates simple Manual junior on the studio and its techniques, initially intended for the students in class of electroacoustic composition.
More information on Audiolexic, Wiki devoted to the Audio and the Music

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