IUB PHYS-P 105 - Signal digitization (2 pages)

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Signal digitization

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Signal digitization


digitization, audio recording and amplifiers

Lecture number:
Lecture Note
Indiana University, Bloomington
Phys-P 105 - Basic Physics of Sound
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PHYS 105 1nd Edition Lecture 36 Outline of Last Lecture I Amplifiers and Tuners Outline of Current Lecture II Signal digitization III Resolution and dynamic range IV Sampling rate and Nyquist sampling theorem V Formats of audio recording Current Lecture I II III Signal digitization Digitization of a time series analog signal requires a sampling rate and a sampling depth Pulse code modulation is a method to digitally represent sampled analog signals In a PCM stream the amplitude of the analog signal is sampled regularly at uniform time intervals and each sample is quantized to the nearest value within a range of digital steps Time division multiplexing is a method of transmitting and receiving independent signals over a common signal path Linear pulse code modulation encodes a single sound channel Support for multichannel audio depends on file format and relies on interweaving LPCM streams Resolution and dynamic range Typical analog electronic has a dynamic range of 40 50 dB due to thermal noise Compact discs employ digital electronics to achieve high fidelity low noise and great dynamic range Sampling rate and Nyquist sampling theorem Sampling rate Bandwidth An arbitrary wave form can be converted to digitized wave form the ADC The correctness of the wave form depends on the time step The sampling rate is expressed in unit of Hz Nyquist Sampling theorem These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV o Reconstruction of a signal is possible when the sampling frequency is greater than twice the maximum frequency o A low pass filter and sampling process can operate according to the Nyquist theorem Aliasing o The misrepresentation of frequencies above half the sampling rate at incorrect frequencies below half the sampling rate o When bandwidth of the digitizing is below the half of the signal frequency the frequency of the digitized signal will fall below the signal frequency Formats of audio recording Popular formats are lossless way format and the lossy compressed mp3 format Waveform Audio Format is a Microsoft and IBM audio file format standard for storing an audio bitstream A CD player uses a laser beam 780 nm solid state laser to control the player and sense the signal which in turn uses several types of coding to avoid problems in data reading and handling such as burst errors

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