At what point does end-to-end delay in a voice conversation generally become unacceptable?

In a voice conversation, end-to-end delay refers to the total time taken for a voice packet to travel from the sender to the receiver and for the receiver's response to be sent back. Generally, for a conversation to feel natural and fluid, there are thresholds for what constitutes an acceptable delay.

The acceptable end-to-end delay for voice conversations is widely considered to be around 150 ms to 250 ms. Delays beyond this threshold can start to cause issues such as increased talk-over and interruptions between speakers, as well as affecting the overall experience of the conversation.

When delay reaches approximately 400 ms, it becomes increasingly noticeable, leading to problems such as awkward pauses in conversation where neither participant knows when the other has finished speaking. At 500 ms, the delay is typically deemed unacceptable for real-time communication, resulting in significant negative impacts on the quality of interaction, making it difficult for participants to maintain a natural conversation flow.

Thus, the threshold of 500 ms is widely recognized as unacceptable for voice communication, as it introduces significant latency that disrupts the conversational dynamics.