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dustbus 2013-8-15 11:08 PM

下=.=

只係學左10log(I/I0)

夠用=.=?

↗亢龍無悔↙ 2013-8-15 11:25 PM

[quote]原帖由 [i]dustbus[/i] 於 15-8-2013 11:08 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=369510847&ptid=22285049][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
下=.=

只係學左10log(I/I0)

夠用=.=? [/quote]你話係maths學左麻:smile_04:,不過都夠做power大3倍果部分

dustbus 2013-8-15 11:41 PM

=.= SOR咁未學:Q :Q :Q

↗亢龍無悔↙ 2013-8-16 12:18 AM

Power 大家3倍, 即係 I = 3I
跟住識做 log 數就計到頭一部分

dustbus 2013-8-16 12:30 AM

The sound intensity level is 60dB, 20m from a loudspeaker.
If the power of the loudspeaker increased by 3 times, what is the sound intensity level at 4m from the loudspeaker.



UM

60=10log(10^12I)
sound intensity=1x10^-6
乘大3倍就唔識了:Q :Q

↗亢龍無悔↙ 2013-8-16 01:50 PM

60 = 10 log ( I / I0 )
new sound intensity level =  10 log ( 3I / I0 )= 10log3 + 10 log ( I / I0 )
= 10log3 + 60



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dustbus 2013-8-16 05:06 PM

感謝龍哥



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