Singing this Note is IMPOSSIBLE!

As a high end audio equipment guy, we deal with this all of the time.  The terms used in our industry are standing waves (force feedback) and phasing.   When placing an object such as a loudspeaker into a room and sending it an amplified signal it produces soundwaves that expand outwards from the speaker, these sound waves bounce of of other surfaces in the room and particularly with bass notes this can create standing waves where the multiple soundwaves in the room and stack up and increase the force (volume) at a specific frequency or they can phase and nearly cancel each other out.   You can experience this yourself by turning on a radio or stereo in a mostly enclosed space setting it to play either test tones or a piece of music that doesn't change much and then walk around the room, particularly near the walls and corners you will notice certain frequencies increasing or decreasing in volume.   With a stereo system if you take the two speakers into the middle of the room and point them toward each other at different distances you can do the same thing, or by rewiring one of the speakers (reversing the polarity of the wires) you can make the speakers out of phase with each and the sound will become very muffled as the speakers are creating nearly opposite soundwaves canceling out most of the sound energy;  Just remember to switch the wires with the power to the system off and switch them back to normal after you are done with the experiment.