Question

Are there limits to human/devices perception?

Answer 1

There's a basic problem that goes with all measurements and that is Noise. Random fluctuations are everywhere, due to temperature, grittiness of very small currents due to individual electrons being involved and other effects. Also there can be interfering signals from other sources. However 'sensitive' your equipment is -i.e. however much you can turn up the gain, there will be randomness. The wider the bandwidth (aka response time and good frequency response) the more noise gets in. To counter this, you can narrow the bandwidth, which means that you need to take longer and longer over your measurement (averaging out the noise) to reach the desired accuracy. The idea that superman could hear someone crying "help" is daft because there would be millions of other people shouting and playing music and he would be hearing the individual air molecules hitting his eardrums. Same thing goes for detecting distant stars in the presence of background light and the heat of the light detector. Taking long enough and using, say, very high power Radar, you could detect the car behind the wall - it's all down to Signal to Noise Ratio.