The experience that I am going to describe now is inspired initially by observation of one patient who was being stimulated electrically in order to induce hearing. This was some years ago. Our attention to this problem was raised by chance when we asked him, in the simple original threshold tests that we were carrying out at the time, to raise his arm whenever he heard the sound. We were stimulating him and he kept raising his arm in fact whenever we were switching off. This was very irritating. We kept turning to our engineers and said ‘I am sure you must have switched it round’ and the apparatus was examined many times. It was only at the end of this that we realised that in fact what was happening was that we were suppressing his tinnitus in an acute manner.