Not sure exactly what you're linokog for in a hostel, but I absolutely loved the place we stayed (was a budget hotel rather than a hostel, though) Pension Sandwirt. It's right by the train station, which is an easy walk from the center of town, but wasn't loud at all. The owner and staff were really nice, and the rooms were big and comfortable. A private double room was 38 Euros per night for both of us. You might be able to find a place slightly cheaper but probably not much. Pension Sandwirt isn't a party place, though, so if that's what you're linokog for you probably won't be interested. Salzburg is a great city, so I'm sure you'll have a great time no matter where you stay. Have fun!