The sounder (aka bleeper) and device (aka tactile) are for visually impaired pedestrians. In Scotland, you can also have a voice telling you the vehicles has a red (e.g. Vehicles heading North on Main Street have been given a red signal).
Systems in other counties have advantages and disadvantages (IMHO), lack of a clear standard compared to background noise. Too complex, so problems in maintenance. However some difference in sounds give a better indication to pedestrians on the start/middle/end of crossing time.
There is also Countdown - http://content.tfl.gov.uk/PCaTS-Note-2-Overview-Presentation...