What is he gets hard when he hears my voice?

It sounds like you are describing a physical or emotional response someone has to your voice. This could be due to a variety of reasons, both psychological and physiological. Here are a few possibilities:

  1. Emotional Connection: If someone has strong feelings for you, hearing your voice might trigger emotional responses, which could include physical reactions.

  2. Conditioned Response: Over time, a person might develop a conditioned response to your voice if past experiences have led to anticipation or arousal.

  3. Voice Attributes: Certain qualities in a person's voice, such as tone, pitch, or rhythm, can be particularly appealing or soothing, potentially triggering a physical response.

  4. Psychological Arousal: Hearing someone they find attractive or are romantically interested in can trigger psychological arousal, which might manifest physically.

It's important to consider the context and nature of the relationship, as well as open communication with the person, to understand the reasons behind their response more fully.