Digital sound processing Part 2
Psychoacoustic model
Using psychoacoustic models, the encoder determines the acceptable quantization noise threshold. The MPEG standard defines 2 psychoacoustic models.
The MPEG audio compression standard allows great freedom in the implementation of the model. The essence of this implementation in a particular encoder depends on the required compression ratio. In consumer applications that do not require a high compression factor, the psychoacoustic pattern may not be present at all. In this case, the bit allocation algorithm does not use the SMR (signaltomaskratio) relationship.
Steps of psychoacoustic models:
1. Using Fourier methods, native sounds are transitioned to their frequency coefficients.
2. The received frequencies are distributed in the critical bands.
3. The spectral values of the critical bands are divided into tonal and non-tonal components.
4. Before determining the noise masking thresholds for different critical bands, the model applies the masking function to signals from different critical bands.
5. The model determines the masking thresholds for each subband.
Conclution
The purpose of researching the abstract topic was to provide the necessary theoretical information in the field of digital sound processing.
In addition, the main summary tasks were completed: identify the principles of psychoacoustics and psychoacoustic models, second, explore digital digital sound compression methods, third, investigate the work of the MP3 format, fourth, formulate the concept of adaptive digital sound coding, and fifth, learn more about digital audio storage and digital audio media.
Based on the above, the following conclusions were drawn.
Psychoacoustics is a scientific discipline that studies the psychological and physiological characteristics of the human perception of sound, based on the fact that the human ear perceives only a fairly small region of the spectrum and tolerates small distortions of sound.
Modern digital audio compression techniques use sophisticated mathematical algorithms and psychoacoustic knowledge. Conventionally, they can be divided into two main types: lossless compression (for example, the flac format) and lossy compression (this includes the popular MP3 format).
MP3 is one of the most widespread and popular lossy digital audio encoding formats. It is widely used in file-sharing networks for evaluative transmission of musical works.
Therefore, today there is a great variety of methods and methods to process an audio signal. Various mathematical models are used to compress digital sound, including adaptive algorithms, as well as knowledge in the field of psychoacoustics. One of the most popular digital audio storage formats is the MP3 format, which uses adaptive lossy data compression technology. Despite the enormous variety of existing methods, software tools for digital sound processing and types of electronic media, this area of multimedia technologies does not lose its relevance for both professionals and ordinary listeners and continues to develop actively.
