A number of newspapers in Australia and the UK have picked up a news item about an experiment in which volunteers drank lots of coffee.
The following is typical -

'In an experiment, volunteers who had consumed ‘high levels’ of caffeine thought they were listening to Bing Crosby singing White Christmas even though the song was not being played.
The researchers described caffeine as ‘the most commonly used psychoactive drug’.
They said the study showed that the health risks of too much coffee need to be addressed.
In the tests, 92 volunteers were asked to listen to a constant fuzzy sound known as white noise.

Professor Simon Crowe, of La Trobe University in Melbourne,  said: ‘We also told them that within the white noise there may be parts of the song White Christmas and if you hear it, press a button.
‘We didn’t include White  Christmas in the white noise  but found that more people  who were very stressed and  had high levels of caffeine thought they heard the song.'

More here - http://www.dailymail.co.uk/health/article-1394873/Drinking-coffee-bring-hallucinations-warn-scientists.html#ixzz1Ob4nA44t