Zur Frage:
ZitatSight is the most common means of establishing a connection with a target (hence the range "Line of Sight"), but by no means the only one. If you physically see, astrally perceive, or touch the target, you can cast the spell.
In situations where the player wishes for their character to use another sense (hearing, smell, echolocation, etc.) to cast a spell, it's up to the gamemaster to decide if that is possible. At the very least, a Perception Test involving the sense in question is called for, with appropriate modifiers (Using Perception, pp.135-136, SR4A). In the case of enhanced senses, the enhanced sense must be integral to the character (i.e., cyberears with audio enhancement would work, but earplugs with audio enhancement would not). Naturally, this works better for Indirect Combat Spells than others.