The everywhere office requires new controls. With headphones, one can modulate sound based on mood and environmental conditions. White noise can paradoxically boost focus, but discrete events and voices in a particular frequency range, say 800 – 1000 Hz, can be extremely distracting. Different chemical balances can also influence the perception of sounds, if not the actual sounds themselves. Sometimes noise requires more noise in order to achieve a kind of silence. Normal headphones offer this, and noise-cancelling headphones turn it into a technical matter: a frequency equal and opposite to the source. The effect is a kind of pressurised tube inside one’s head where MP3s can drift across the vacuum.