When opening a hive window last summer I heard the queen piping* in response to the ingress of light. Humans communicate with speech, touch, eye, facial expressions and body movement. When we open a hive it's good to remember that smell, your footsteps, movement speed, tool use, fear/calmness, temperature, weather, atmosphere and light are all communicating something to the bees.
It didn't matter which window on the stack of four boxes I opened. Each was met with the sound of a piping queen and it stopped when the window closed - I had invaded. I try to curb the desire to look, to always know. I ask myself, what is the purpose of looking? and is it for the good of the hive?
*It is believed that by piping queens inform other queens about their presence and prevent emergence of more than one queen at a time. Another function of piping could be communication between young queens in order to asses their fighting abilities. It is also possible that queens pipe to prevent worker aggression as workers will often freeze when they hear a piping queen