If you use the new version 6 update from TomTom for Go, 300, 500, 700, X Series, One, Rider.
tomtomsatnav.info/version6.html
With version 6 and above it is no longer necessary to modify the data.chk file to add custom warning sounds to your device. If you add an ogg audio file with the same name as the poi to your map folder the software will automatically use that sound to warn of the poi.
As an example to have a poi file called tescos.ov2 and want a custom warning, these are the files you will require -
tescos.ov2 This is the poi information used by the map data
tescos.bmp This is the icon displayed on your screen.
tescos.ogg This is the audio file used for the warning.
All three files should be copied into your map folder.
The software will automatically us the ogg audio file for the warning. When you set up the warning the software will not allow you to select a warning sound just the warning distance.
if you download the low bridge voice’s from here amngps4.wanadoo.co.uk/poifil.htm
and used Audacity to save them as ogg files they work with the tom tom.
you can set all bridge warnings with a spoken voice.
audacity.sourceforge.net/
david