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Ratioed beating freqs

Sorry, but I am a little slow on the math side of things. Can anyone tell me how to perform the following calculation?

I need to generate a beat frequency, but the originating frequencies have to be distributed in a certain numerical ratio.

For example, if I want to generate a 4400Hz beat, it needs to be derived from the single case where the two original sinewaves have a set 1.0:0.6 frequency ratio between them.

Could someone please walk me through it using the above figures for clarity?

Many thanks,

Bill Coon

Reply to
William Coon
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"William Coon"

** The audible beat frequency = f1 - f2 ( f1 being higher)

In your case f2 = 0.6f1

and f1 - f2 = 4400

so 0.4f1 = 4400

giving f1 = 11000

and f2 = 6600

Note:

the true beat frequency is ( f1-f2 )/2 but the ear hears the positive and negative maxima the same.

....... Phil

Reply to
Phil Allison

The frequency difference between the two source sine waves is 4400Hz, so we can write:

df = 4400Hz = |f1 - f2|

where f1 and f2 are the two source frequencies. You can arbitrarily assume that f1 > f2 without loss of generality (since f1 and f2 are interchangeable unknowns) and write:

df = f1 - f2

You also specify that f1 = (1.0/0.6)*f2 = (5/3)*f2 for some choice of f1 and f2. Let r = (1.0/0.6), then you can write:

df = r*f2 - f2 df = f2*(r - 1)

In the example given,

4400Hz = f2*(5/3 - 1)

4400Hz = f2*2/3

f2 = 6600Hz and f1 = f2 - 4400Hz = 2200Hz

Reply to
Greg Neill

"Greg Neill"

** Obviously wrong.

f1 = f2 +4400 = 11000.

........ Phil

Reply to
Phil Allison

Simple math as in 1+1=2.

Reply to
Robert Baer

Oops. My bad. Thanks.

Reply to
Greg Neill

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