You are tasked with developing a streaming Dataflow pipeline to monitor noise levels from hundreds of sensors stationed near various construction sites throughout a city. Each sensor records noise levels every ten seconds and sends data to the pipeline whenever the noise level exceeds 70 dBA. Your objective is to calculate the average noise level from a specific sensor when the duration of received data extends beyond 30 minutes; however, the calculation window should close if no data is received for a continuous 15-minute period. What steps should you take to achieve this?