Is it possible to low pass filter the amplitude of a sound wave? Is it physically possible to block or attenuate noise above a certain amplitude, but leave other lower amplitude noises unhindered? 
 A: Remember that noise is unwanted frequency signal superimposed into the original frequency. This means to reduce noise, you need to block the unnecessary frequency components. The effect of noise increases while increasing the amplitude because amplitude is a measure of loudness. So the amplitude (loudness) of the noise also increase as you increase the amplitude of the sound wave. That doesn't mean you can make the noise disappear by doing something on the amplitude. By reducing the amplitude, you also reduce the amplitude of noise and the noise will stay "silent". In order to reduce noise you must use a filter and the purpose of filter is to select a particular range of frequency and block the remaining frequencies. You cannot "block" the noise by selecting a particular amplitude. But the effect of noise can be hidden up to a certain limit by decreasing the loudness or amplitude. If the noise is too hgih and it's amplitude is comparable to the audio amplitude, it's better to switch off the player.
