Best answer by Anonymous
To switch off the sounds on your IHD unit, you'll need to press the OK button to access the main menu. Here you'll have an account information section (including your meter balance, tariff and standing charge) - the second section 'Adjust settings' is the one you'll need.
Here you have two options - set a budget and key tones (off/on) - this will give you the option to turn the sound off. Just keep pressing OK on your IHD to reach this option.
Hope this helps,