In this paper, we design and implement a prototype system with an adaptive intra-media synchronization scheme for haptic interactions in distributed virtual environments (DVEs). In order to interact with haptic interfaces in the DVEs, we require a stringent level of QoS service from the network. Especially, network delay jitter and packet loss over the Internet may seriously degrade the output quality of haptic media in the DVEs. The proposed system model consists of three layers (application, synchronization, and network) to support haptic interactions over time-varying IP networks. The intra-media synchronization scheme implemented in the system controls buffering time and transmission rate to enhance the QoS of networked haptic interactions. To demonstrate usefulness of the proposed scheme, we simulate it by using NS-2 simulator and implement simple haptic-based
DVEs. According to the simulation results, the proposed scheme provides more stable playout of haptic data under network delay jitter. Moreover, when lots of clients are participating in the DVEs, it can decrease the transmission rate of haptic data so that we can get smaller network delay. According to the experiment results, the proposed scheme can be applied to the real DVEs under network delay jitter.