Freesound is a repository of sound files categorised by user-defined tags. Through those, you can spot what other users have labeled industrial sounds but be prepared that some of those might be artificially created (so, not really a recording of an engine but something that sounds like an engine).
In the same category is also Soundsnap.
The other popular ...
The IEEE used to host something called the Signal Processing Information Base, which is gone but there is a mirror at:
There is also some links from Mike Porter's Ocean Acoustics Library at:
ARMA divides the signal into two parts and that models the two parts.
Financial time series are corrupted by different types of correlated and uncorrelated noises with definite functions that allow modeling and others more difficult as per having to use aproximations. In addition financial or economic times series may exhibit long memory processes (Black ...
What you are suggesting is indeed rooted on concepts that are important in DSP:
On the channel coding side, you have for instance error correction codes (or error correcting codes, both ECC)
On the source coding side, since you mention Sudoku, techniques like matrix completion, sparse sampling or compressive sensing are possibilities to approximately ...
Things like the good ole' GSM standard specify power delay profiles and a phase variation model. So, there you go, reference model delivered in the shape of a standard.
Other than that, if you're just looking for any ISI-inducing (i.e. frequency-selective) channel, why not use your favourite DSP framework to come up with a random FIR filter?
Also, a lot of ...
That is a simple question:
All sound that passes into analogue domain using digital audio converters (DACs) have a SNR inferior to about 113 at best, and more probably 96-100... everything recorded using microphones will have inherant noise, unless the recording has been copy pasted onto a silent track leaving intervals of silence.
So what you need to do ...