sound decade ?
I understand the octave which relates to the doubling of pitch, cent
which is 1/1200 of an octave. Cents are used in tuning and the good
ears can tell a diference of about 3 cents. My imagination seems
limited in understanding what's so great about plotting on log-log
paper. And why is the knowledge of sound decades so limited? From 30
to 15,000 Hz there's 2.7 decades, 8.97 octaves and too many cents. The
book points out that all visible light is one octave making the audible
spectrum much more complicated if you look at it from that standpoint.
In a multiband shortwave radio each band is approximately an octave
because that's all a LC circuit can span.
--
73
Hank WD5JFR
"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
I just got the book Sound System Engineering by Don Davis and Carolyn
Davis and it has 2 short sections on sound decades. Defined as:
HF/LF=10**1=1 decade HF is highest freq and LF is lowest freq
or
HF/LF=10**x decades
or
(Ln HF - Ln LF)/Ln 10 = x decades
An example for a span of 30 to 15,000 Hz
x decades = (Ln 15,000 - Ln 30)/Ln 10 = 2.7 decades
Ok, I think I understand the math but what is a practical application
of
a sound decade?
It's just a convenient way of thinking about pitch changes. Sometimes
it can make the math easier to think about decades instead of octaves,
especially if you are plotting responses on conventional log-log paper
where there is a cycle every tenfold increase.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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