I use a lot of visuals in my flash cards, ie the question will be a word and then the answer will be a visual that shows its meaning. I am thinking about doing the same for audio clips. I would select a spoken sentence using a system like Audacity which would be the prompt and then the answer as plain English text. Obviously it is a lot of work and the file might end up being huge.

Has anyone already got any experience doing this?

I have in the past done this a lot to make flashcards for the Anki flashcard system. This is a free downloadable and customizable flashcard system that is easy to use and although it is not connected to lingQ, you can export your lingQ vocabulary and cut and paste your hints, etc. into the Anki flashcard system. I have to warn you though that making the sound clips and finding good pictures on the web can be very time consuming and become a huge distraction. Unless you really enjoy it, an argument might be made that you would be better off spending your time just reading, listening and making and reviewing lingQs if you want to learn faster. However, I have to admit that the lingQ flashcards don't really inspire me to review them the way my own homemade audiovisual and customized Anki cards do. On the other hand, making and reviewing flashcards tends to feed my need to get things perfect which I have heard may actually be a hindrance to learning a language as compared to getting lots of exposure to comprehensible input. In any case, if you like flashcards, and have not tried Anki, check it out at http://ankisrs.net/ and good luck!

Thank you for the link. I have been trying to create my "homemade" flash cards in many different ways. But I have never thought about that audiovisual(actually I did not understand how it is exactly.) I have to say though I love to read and listen my lessons at LingQ I feel often quite lazy to review my flash cards here.

I find pictures on the web using google images, then I cut and paste into jpg files using adobe photoshop elements and simply attach file to the card. For audio, I use audacity and export selection and attach to the card. It's hard to find individual words but easy to get whole sentences or phrases from the audio content you're studying as long as you can get the mp3. You can set up the cards to have the question as audio only, target language text or your own language text with the appropriate answers.Fonts can be customized and if you know some script writing you can get stuff to show up with mouse overs (I use to bring up kana symbols when I mouse over the kanji, or show the mnemonic for remembering kanji), change font (which I used for Russian script vs block letter fonts) and link to web sites on clicking and many other cool things which I don't even understand but wish I did. I don't know any programming but I have been able to cut and paste and tweak a little bit of handy script I found in files that are shared on the anki website. Have fun!