Audio. Digital and analog audio
Despite the fact that most of the external information we acquire with the help of sight, sound images are no less important to us and often even more. Try watching a movie with the sound turned off; in 2-3 minutes you will lose the thread of the plot and interest in what is happening, no matter how large the screen and the high quality image. Thus, a pianist played off-screen in silent movies. If you remove the picture and leave the sound, the movie can be “heard” like a fascinating radio show.
Hearing gives us information about what we do not see, since the visual perception sector is limited and the ear captures sounds from all directions, complementing visual images.
Hearing gives us information about what we do not see, since the sector of visual perception is limited and the ear captures the sounds that come from everywhere, complementing the visual images. At the same time, our hearing with great precision can locate an invisible sound source in direction, distance, speed of movement.
They learned to convert sound into electrical vibrations long before images. This was preceded by a mechanical recording of sound vibrations, whose history dates back to the 19th century.
Accelerated progress, including the ability to transmit sound at a distance, was made possible by electricity, with the advent of amplifying, acoustic, and electro-acoustic equipment and transducers – microphones, pickups, dynamic heads, and other emitters. Today, audio signals are transmitted not only over cables and over the air, but also over fiber optic communication lines, primarily in digital form.
The acoustic vibrations are converted into an electrical signal, usually by microphones. Any microphone contains a moving element, the vibrations of which generate a current or voltage in a certain way. The most common type of microphone is the dynamic, which is a reverse speaker. The vibrations of the air set in motion a membrane that is rigidly connected to a moving coil in a magnetic field. A condenser microphone, in fact, is a condenser, one of whose plates vibrates at the same time as the sound, and with it the capacitance between the plates changes. Ribbon microphones use the same principle, only one of the plates is freely suspended. Similar to a condenser electret microphone, whose plates, in the process of oscillation, generate by themselves an electric charge proportional to the amplitude of the oscillations. Many models of microphones have a built-in amplifier (the signal level directly from the acoustic-electric transducer is very low). Unlike a microphone, the pickup of an electric musical instrument registers vibrations not from the air, but from a solid body: a string or the soundboard of an instrument. The cartridge reads the record slot using a needle mechanically connected to moving coils in a magnetic field, or magnets if the coils are stationary. Or the vibrations of the needle are transmitted to the piezoelectric element which, under mechanical stress, generates an electrical charge. In magnetic recording, an audio signal is recorded on a magnetic tape and then read with a special head. Finally, optical recording was traditionally adopted in cinematography: an opaque soundtrack was applied from the edge of the film,
In synthesizers, sound is born directly in the form of electrical vibrations, there is no primary transformation of acoustic waves into an electrical signal.
Modern autumn sound sources are diverse and digital media are becoming more and more common: CDs, DVDs, although vinyl records are also preserved. We continue to listen to radio, both terrestrial and via cable (radio hotspots). Sound accompanies television shows and movies, not to mention a phenomenon as familiar as telephony. A computer receives an increasing share in the world of audio, allowing it to conveniently archive, combine and process sound programs in the form of files. In the digital age, digitized speech and music are transmitted through digital channels, including the Internet, without serious losses in transportation. This is provided by digital encoding and the loss is due solely to compression, which is used most often. However, in digital media, either it does not exist at all (CD, SACD), or lossless audio compression algorithms are used (DVD Audio, DVD Video). In other cases, the degree of compression is determined by the required level of soundtrack quality (MP3 files, digital telephony, digital television, some types of media).
