Light is faster than Sound

After the maturing of the Surat (the soul's power of hearing) and of Nirat (the soul's power of seeing) the soul is freed from the bondage of the body and rises to the higher regions. It then gains freedom from birth and death. 

Reference is made to this fact in the Sar Bachan.

I will follow the lead of Nirat and reach Sat Lok.

In the beginning the Sound alone is manifest. The Light appears later. In practice also, we first rely upon the Sound, although we begin with Simran (repetition) and Dhyan (contemplation). Their function is to prepare the ground for hearing the Sound. Simran and Dhyan have their own functions, but they merely act as pilots or advance-guards for the bridegroom – the Shabd which alone really counts. 

Simran is the key to the practice of listening to the Sound. During his practice the seeker comes across regions in which he is surrounded by effulgent Light. For crossing the brilliance of this Light, the Sound is the guide. 

There are some regions where it is complete darkness, like Maha Sun, the Great Void. There also the Name given by the Master is the only guide. In these regions, the Sound is the only true pathfinder or guide. It is just like a traveller trying to find his way to a habitation when he is lost in a lonely jungle and enveloped in thick darkness, by following the barking of a dog. The Sound helps the blind seeker within in similar circumstances. 

This is the superiority of the Path of the Sound Current.