It is common place when you're in a meeting in person or even a video web conference, to make eye contact with the person to whom you want to respond to your comment or question. This in turn, alerts that person and cues them respond to you. However, you will not have the luxury of making eye contact during an audio conference. As such, it is recommended that you say the name of the person with whom you wish to speak prior to asking a question or making a statment. For example, you would have to specifically ask an attendee - "Ron, where do we stand on those TPS reports?"