Introduction to Sound PDF

Introduction to Sound  What is a Signal? A signal is a pattern of variation of some form Signals are variables that carry information A signal is any physical quantity that is represented as a function of an independent variable Examples of signal include: Electrical sign...

Introduction to Sound  What is a Signal? A signal is a pattern of variation of some form Signals are variables that carry information A signal is any physical quantity that is represented as a function of an independent variable Examples of signal include: Electrical signals: Voltages and currents in a circuit Acoustic signals: Acoustic pressure (sound) over time Mechanical signals: Velocity of a car over time Video signals: Intensity level of a pixel (camera, video) over time  What is a Signal? 1D/2D/3D signals: 1D signal=f(x); x=time, distance, etc. (1D signals with amplitude, pressure, intensity, etc. as a function of time, f(t)) 2D signal=f(x,y); x,y=spatial positions (images as functions of 2 spatial coordinates) 3D signal=f(x,y,z); x,y,z=spatial positions (images as functions of 3 spatial coordinates)  Signal and noise Every signal carries information but not all of that information is important. The goal of signal processing is to extract the useful information from the signal. The part of the signal that is not useful is called noise. Noise is any part of the signal we are not interest. Signal and noise  Analog-to-Digital Conversion The physical world around us exists in a continuous form  Sensing light  Sensing sound energy.  Sensing pressure.  Sensing temperature.  Sensing motion.  Analog-to-Digital Conversion A signal is analog if it can be represented by a continuous function. Digital signals are represented by a discrete set of values defined at specific (and most often regular) instances of the input domain, which might be time, space, or both. We need a process of : Analogue to Digital Conversion  Analog-to-Digital Conversion Analogue signal Digital signal 0 0 Represented by a continuous function Represented by a discreet set of values  Analog-to-Digital Conversion Advantages of digital signals:  It is possible to create complex, interactive content (In the digital medium, we can access each unit of information for a media type).  Stored digital signals do not degrade over time or distance as analog signals do  Digital data can be efficiently compressed and transmitted across digital networks.  It easy to store all types of digital media on a common storage medium.  Analog-to-Digital Conversion Analogue signal Digital signal Sampling and 0 0 quantization Interpolation