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Question
Hello my question is if 7 DBWs (Decibel Watts)is equal to 5 watts,does it take 5 watts to hear 7 decibels of sound?
No; a db is a ratio of one level to another. It is only absolute if referenced to a specific level.
For example, if an amplifier is producing 5 watts out for a given signal input and that input signal is increased such that the output power now goes up to 10 watts the increase in db is 3db. In other words, 3db relates to a 2/1 power change.
Sound level is a completely different matter. Acoustic energy does not relate directly to electronic power.
A useful specification to consider is loudspeaker sensitivity. It is usually given in dbw. And sensitivity is given as the sound level produced at 1 meter with a 1W input to its terminals.
This is a pretty good summary of the acoustic or sound power watts:
http://en.wikipedia.org/wiki/Sound_power
O db sound level is about the loudness of a whisper.
Does this help? Let me know if you need more.
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Answers by Expert:
Cleggsan
Expertise
Audio Design Engineer; systems, loudspeakers, cd/dvd players, etc. I am knowledgeable in all high end audio equipment and installations. MAKE SURE YOU GIVE A MAKE AND MODEL NUMBER AND CAR IF IT IS AN AUTO QUESTION. Note: I am getting some who ask good questions that take a lot of time to research but then the questioner fails to read the answer. Please don't ask questions unless you are seriously looking for an answer. If you find an answer to your question otherwise then let me know with your reply. Thank you.
Experience
Have been associated with audio design, standards, testing and component systems for over 40 years.
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Life Fellow Member of Audio Engineering Society
Life Senior Member of Institute of Electronic and Electrical Engineers
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Review technical manuscripts for IEEE Spectrum
Write occasionally for high-end audio publications
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BSEE/MSCS/MBA
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Past Employee/advisor to several well known audio products manufacturers
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