Do soundproof windows need angled glass?

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?
Source: www.record-producer.com

Power amps: Class A, Class, B and Class D
Your power amplifier may waste more energy as heat than it turns into sound. But some amplifiers are close to 100% efficient. How does class make the difference?
Source: www.record-producer.com

Will a $140,000,000 record deal make you happy?
So a guy gets a $140,000,000 record deal. And more than half the visitors to this website haven't even heard of him. In which universe does this make sense?
Source: www.record-producer.com