A Doppler effect occurs when a source of sound does what?

Is the speed of sound independent of frequency? Explain.

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#4

A sound of 60 dB is OOOO 2 times as intense as a sound of 40 dB 1.5 times as intense as a sound of 40 dB O4 times as intense as a sound of 40 dB 1,000 times as intense as a sound of 40 dB 100 times as intense as a sound of 40 dB 16 times as intense as a sound of 40 dB 20 times as intense as a sound of 40 dB 10 times as intense as a sound of 40 dB O 8 times as intense as a sound of 40 dB

The sound level measured in a room by a person watching a movie on a home theater system varies from 45 dB during a quiet part to 65 dB during a loud part. Approximately how many times louder is the latter sound?