transformation of independent variable

[bhuvanesh]

i am learning signals and system from yesterday. Today i have crossed topic called"transformation on independent variable ". Under that there is 1)time scaling 2)time shifting 3)time reversal

i would like to know where we use this operation. Myself found that time scaling is used when we need to compress date(time compression) and when we want to recover the compressed data(expanison).

But i want to know that application or where we use the time shifting and time reversal.Thank you in advance

 

[Merlin3189]

Time shift could be a delay and all circuits have delays.

But generally these transformations are not so much things that "happen" to signals, but mathematical operations we perform, either in processing the signals or in calculating what happens to them.

Time reversal and time shifting are used in convolution and thus in determining or setting circuit response functions.

Time scaling might be something like speeding up or slowing down an audio signal.

Also, although you bring them up here in the context of time as the independent variable, these are just mathematical tricks that can be performed on lots of functions, irrespective of the variable. All of these transforms crop up in image processing where there are functions of space: just think of magnification, translation (moving) and reflection. Then think of rotation. Easy in an image context, but what does it mean for an audio signal?!