Publisher's Synopsis
In our daily life noise of course refers to loud, disagreeable sound without any musical aspirations. In the early days of radio communication the word noise was introduced to describe "any unwanted (electrical) signal within a communication system that interferes with the sound being communicated", which is thus audible as "noise" on a headphone. Interference is noise that tends to obscure the useful signal. It is usually caused by electrical sources but can be induced from other physical sources such as mechanical vibration, acoustical feedback, or electrochemical sources. In addition to characterizing noise by its source, it is useful to distinguish noise by its frequency spectrum and amplitude distribution. When noise power has a flat frequency distribution, it is called white noise (from the analogy of white light containing all frequencies). The importance of noise analysis becomes immediately clear when one realizes that the quality of experimental data is not determined by the absolute strength of the signal, but rather by the ratio of signal strength over noise strength. Digital signal processing techniques are increasingly replacing conventional analog signal processing methods in many fields, such as speech analysis and processing, radar and sonar signal processing, biomedical signal analysis and processing, telecommunications, and geophysical signal processing. An important application of digital signal processing methods is in determining in the discrete-time domain the frequency contents of a continuous-time signal, more commonly known as spectral analysis. More specifically, it involves the determination of either the energy spectrum or the power spectrum of the signal. In many consumer products, e.g., cellular phones and handheld computers, both digital and analog circuits are required. Nowadays, it is possible to implement a large subsystem or even a complete system, that earlier required several chips, on a single chip. A system on chip has generally the advantages of lower power consumption and a smaller fabrication cost compared with multi-chip solutions. The switching of digital circuits generates noise that is injected into the silicon substrate. This noise is known as substrate noise and is spread through the substrate to other circuits. The substrate noise received in an analog circuit degrades the performance of the circuit. This is a major design issue in mixed-signal ICs where analog and digital circuits share the same substrate. Speech, music, and even environmental signals can serve as wanted or unwanted sounds, depending on all these factors. To this end, the hearing aid industry has been challenged to develop schemes and algorithms that provide some relief from those unwanted sounds to hearing-impaired hearing aid users. Advanced Digital Signal Processing and Noise Reduction provides a lucid and designed presentation of the theory and applications of statistical signal processing and noise reduction approaches.
