On the question of sound processing
Sound processing should be understood as various transformations of sound information to change some characteristics of sound.
Sound processing includes methods for creating various sound effects, filtering, as well as methods for cleaning the sound of unwanted noise, changing the timbre, etc. This whole huge set of transformations ultimately boils down to the following basic types:
Amplitude transformations. They are carried out on the amplitude of the signal and lead to its amplification / attenuation or change according to some law in certain parts of the signal.
Frequency conversions. They are performed on the frequency components of the sound: the signal is presented in the form of a frequency spectrum at regular intervals, the necessary frequency components are processed, for example, filtering and reverse “folding” of the signal from the spectrum. on a wave.
Phase transformations. Phase shift of the signal in one way or another; for example, such transformations of a stereo signal allow the effect of rotation or “three-dimensional” sound to be realized.
Temporary transformations. Implemented by overlaying, stretching / compressing signals; They allow you to create, for example, echo or chorus effects, as well as to influence the spatial characteristics of the sound.
The discussion of each of the named types of transformations can become a complete scientific work. It is worth giving several practical examples of the use of this type of transformation when creating real sound effects:
Echo (echo). It is implemented through temporary transformations. In fact, to get an echo, it is necessary to superimpose a delayed copy of the original input signal. In order for the human ear to perceive the second copy of the signal as a repetition and not as an echo of the main signal, it is necessary to set the delay time to approximately 50 ms. On the main signal, you can superimpose not one copy, but several, which will allow you to obtain the effect of multiple sound repetitions (polyphonic echo) on the output. In order for the echo to appear muffled, it is necessary to superimpose on the original signal not only delayed copies of the signal, but also dull in amplitude.
Reverberation (repetition, reflection). The effect is to add the spaciousness of a large room, where each sound generates a corresponding sound that slowly fades away. In practice, with the help of reverb, you can “revive”, for example, a phonogram made in a muffled room. Reverb differs from the “echo” effect in that a delayed output signal is superimposed on the input signal and not a delayed copy of the input signal. In other words, the reverb block is simplified as a loop, where the output of the block is connected to its input, so that the already processed signal is fed back to the input every cycle, mixing with the original signal.
