I have been recording keypress from laptops using my phone and it seems that I get better results when both the laptop and the phone are placed on a hard surface like a wooden table than when they are on separate surfaces like different tables or when the phone is handheld. Is the transmission of sound affected by the surface, and how does it alter the recording of the sound?
Are you using your mobile phone to record the keypress? If so, then yes. The microphone in your mobile isn't the best for SFX recording, especially small sounds like keypress. Having your phone on the table with your keyboard will allow the propagation of sound to reach your microphone in a more direct fashion.
When recording with your phone from above, the sound of the keypress travels through the air into the microphone of your phone. When recording with your phone on the table, the vibrations travel a lot quicker and more direct into your phone because its a mainly solid transmission.
There's a wiki article here all about sound http://en.wikipedia.org/wiki/Sound
I wonder why I answered this... It's probably something we shouldn't be getting here.
Surface as amp is an often mentioned technique in texts on recording foley. I myself don't like the sound of a keyboard on a hard surface, usually the surface resonates too much, but on the other hand, on anything soft a keyboard can sound really thin. That said, the project dictates the sound you're after..
don't record avoid recording with a phone, smart or not. The engineering tradeoffs inside it destroy the sound. The graph below is only part of the story.
graph from here.