Question regarding sound waves

[Himura Kenshin]

Question regarding on sound waves.

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Hello,I just join in as member yesterday.Sorry to interrupt that I have question to ask.Here's the question.

1.Two small speakers emit sound waves of different frequencies.Speaker A has an output of 1.0mW and speakerB has an output of 1.5mW.Determine the sound intensity level (in dB) at point C if

(a) only speaker A emits sound (Answer 65.0 dB)
(b) only speaker B emits sound (Answer 67.8 dB)
(c) both speakers emit sound (Answer 69.6dB )

I have try searching for the similar question on reference book but can't find any question similar to this.I still can't figure out the answer.


Thank you for anyone who help in solving this question.I really appreciate it !!!!

[Tide]

Do you know the relative positions of the two speakers and the location of point C?

[Himura Kenshin]

Sorry for not including the information you need.

(Distance of speaker A from O is 3.0m and the distance of speaker B from O is 2.0m.Point C is horizontally at a distance of 4.0m from O)

Thanks for giving help in this question.