Do soundproof windows need angled glass?

If you have ever visited a professional recording studio, or even just seen pictures, you may have noticed that the window between the control room and recording area has angled glass panes. Is there a good reason for this, or is it just for show? If you have ever visited a professional recording studio, or even just seen pictures, you may have noticed the window between the control room and recording area. There has to be very good soundproofing between these two areas so that the engineer can have the monitors as loud as he or she wants, but no sound energy leaks through into the recording area to be picked up by the microphones. Also, you don't want sound leaking directly from the recording area to the control room, otherwise you wouldn't be able to judge properly from the monitors whether the microphone selection and positioning was right. So the studio window is commonly made of three panes of thick glass. Commonly the panes are all of different thickness, but this is an issue ...