I think sound is the most apparent medium to calm our mind.
Sound can be described as external sound which comes from a external sources and which can be heard by our physical body parts.
For example when a dog bark, we can be easily recognized that it was a barking sound and it was coming from dog , i.e, the source.
But in the case of Inner sound we cannot identify the source . It comes from within,to hear this we can meditate because to feel it, One should increase their concentration to withdraw their attention from all the external sources.
All of us have busy lifestyles and we think we can't meditate because we misinterpret it's meaning.Meditation don't need a specific place or time. It can be done anywhere anytime.
I know all of you might be thinking that how it is possible to make ourself free from distraction in a crowded place. Meditation is not something that needs concentration it is a practice to increase concentration. So, tougher the circumstances more perfection is there.
Let me explain it to you with the help of an example.
Suppose that you are a maths student. You have practiced the most tough questions. You are prepared for the worst phase then when you will have an easy question. You will easily solve it and if you will get tough question you are prepared for it.
Similarly, when you know how to meditate in crowded place, you practice mediation then you are prepared to do it anyway anywhere.
One Of the effective way is to take a candle and meditate with it. See its Flame and focus take a deep breath.
You will feel calmness in you mind. No extra thoughts nothing. You will be able to solve your problems more effectively. It will increase your patience and help you in thinking clearly.
It is also proven that inner sound meditation has various positive effects on our health like :-
1. Control over anger
2. Understanding in relationships
3. Increases concentration.
4. Improves problem solving.
It also cures some diseases and keep us healthy.You can see this link for more information
I really don’t know how do I explain what it is all I can tell you is that it has some mysterious effect which is very soothing peaceful.
When you meditate you want to live in that moment it he some power. And I am so sure about it because I have experienced it.
If we learn to focus then we can achieve everything. - 
