This makes sense for a couple of reasons, says psychologist Dr Nick Perham, at Cardiff Metropolitan University in the UK, who studies the effect of sounds on learning but was not involved in the study. Firstly, he says, sounds that are most distracting tend to be very variable. A general hum in the background suggests a steady-state sound with not much acoustical variation. “So there’s not much there to capture your attention – nothing distracting the subjects,” he says. At the same time, the background noise might cause the subjects to be in a slightly heightened state of arousal, says Perham. You don’t want too much or too little arousal. “Medium arousal is best for good performance. So it might be that a general hum in the background gives an optimum level of arousal.” With that in mind, Perham suggests there may be some benefit to playing music or other sounds in an art class or other situations where creativity is key.