1. Use a light touch. When you hammer on, you don't need to press down hard on the string. A light touch will help you avoid creating any unwanted noise.
2. Mute the other strings. Before you hammer on, use your fingers to lightly touch the other strings to mute them. This will help to prevent them from vibrating and creating a rattling sound.
3. Use the correct technique. When you hammer on, you should use your picking hand to strike the string and your fretting hand to hammer the string down onto the fret. Make sure that you are using a smooth, controlled motion.
4. Practice. The best way to get better at hammer-ons is to practice. Try practicing for a few minutes each day, and you'll eventually be able to play hammer-ons without any rattling sound.
Here are some additional tips that may be helpful:
* Use a bass with a good setup. A bass that is properly set up will be easier to play and will produce a better sound.
* Use the right strings. Not all bass strings are created equal. Some strings are more prone to rattling than others. Experiment with different strings until you find ones that work well for you.
* Experiment with different techniques. There are many different ways to play hammer-ons. Experiment with different techniques until you find one that works best for you.
* Be patient. It takes time to learn how to play hammer-ons properly. Don't get discouraged if you don't get it right away. Just keep practicing, and you'll eventually be able to play them like a pro.