Musical Acoustics, Combining frequencies of two instruments

AI Thread Summary
To estimate the operating frequency of brand X, the problem involves understanding the concept of beats in acoustics, where the beat frequency is the difference between two sound frequencies. Given that one whistle operates at 21.5 kHz and a beat frequency of 5 kHz is produced when both whistles are played together, the equation can be set up as 21.5 kHz - X kHz = 5 kHz. Solving this gives X = 21.5 kHz - 5 kHz, resulting in an estimated frequency of 16.5 kHz for brand X. The confusion regarding negative frequencies arises from misapplying the beat frequency concept, which should always yield a positive result. The final answer for brand X's operating frequency is 16.5.
mhmil
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Homework Statement



A certain dog whistle operates at 21.5 kHz, while another (brand X) operates at an unknown frequency. If neither whistle can be heard by humans when played separately, but a shrill whine of frequency 5000 Hz occurs when they are played simultaneously, estimate the operating frequency of brand X. (Find your answer in kHz, not Hz, but do not enter units. So if you think the answer is 2000 Hz = 2.0 kHz, enter 2.0 )


Homework Equations



Unsure.


The Attempt at a Solution



I've tried 21.5khz + X khz = 5khz and solved for X, -16.5 khz. This doesn't make any sense, as how could it be negative? My homework doesn't accept this as an answer either (obviously.)

Any help would be greatly appreciated.
 
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Beats are the difference of two frequencies.
Fw2 = Fw1 + or - F(beat).
 
Thanks!
 
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