I have a cultus 2003 and I used to get a same noise when the engine was cold when I use to run the car and when it got hot the noise used to disappear, its likely with every suzuki out there I heard of now I went to check it with a mechanic and he said gear oil is less.
i had changes the gear oil only a few months back and i knew it was ok then I went to another shop to get it check ( always get an opinion from atleats 3-4 mechanics about the issue you face cause you will get different reviews from each one )
So he told me that your gear oil is ok BUT its not thick so you need to add STP to your gear oil and it will do.
So I took out all the oil which was in the gear and added 2 cans of STP ( 1 costs 110pkr) and added the gear oil (Caltex) and I gave it a run for about 20km then I could only check for the sound the next day so when I started it the sound was still there but after running around 50-60km the next day the sound was GONE.(H)
SO I suggest you chk whenther the noise is coming from the gear or the belts.