How do we represent 'smell' and 'taste' as signals? I was wondering if we could represent 'smell' and 'taste' as signals like we do for audio. How do we mathematically represent them? Is there any research papers related to it? Can someone give me related links or book titles etc?
 A: It is not as simple as it seems. Sound is a wave that can be represented by the intensity of one single variable as a function of time (I am talking of the simplest case which is a monaural sound). Flavor and smell, instead, depend on chemical signals, that interact in complex ways with an array of different body sensors. You cannot represent it by a single signal, and the variety of chemical compounds is huge. However, there are ways to simplify the problem a little bit. 
Smell is more difficult and less understood than flavor, but there are already attempts to code it. See for instance http://computer.howstuffworks.com/internet-odor1.htm.
Taste is also complex, because it depends not only on the 5 basic chemical receptors, but also on food texture, temperature and other variables. However, the state of the art for a universal taste synthesizer is pretty advanced. You can read  http://www.dailymail.co.uk/news/article-2328816/NASA-build-universal-food-synthesizer-create-3D-food-printer-insects-algae.html 
A: i will give another answer (or maybe two related answers).


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*Smell and taste as raw signals relate to specific molecules and their bio-chemical properties which cannot be simulated electronicaly. Not to mention the brain processes involved (do we actually see the same color or just agree on same name of a color?). On the other hand, audio or visual signals, which are not related to specific molecular and bio-chemical properties, but rather on wave properties which can indeed be simulated and re-constructed (e.g the speaker of the stereo player re-constructs the audio signal from encoded information). Can a speaker re-construct the molecule which is the source of a specific smell or taste?

*Indeed one can represent smell and tatse as electronic signals (in a more limited manner), as such. create a database of codes mapped to specific smells or tastes (or mapped to specific molecules and bio-chemical substances). These are used as references. take a sample smell and map it to the database, send the database id, let the other side look up the database id sent and then generate the specific molecule (or bio-chemical substance) which is indexed by the sent "smell" id. This way it can be done, but it is limited.
