# Sound word problem.

#### Dx

A certain dog whistle operates at 23,5khz, while another brandX operates at an unknown frequency. If neither whistle can be heard by humans when played seperately but a shrill whine of frequency 5kHz occurs when they are play simultaneously, estimate the operating frequency of brand X.

do i have to subtract the 23.5k from 5 to find its difference? Since beat frequency = differ in the 2 wave frequncies or what? I am confused with what to do?

Thanks!

Dx

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#### gnome

You're on the right track but in the wrong direction. Keep in mind that humans can hear up to about 23 kHz, while dogs hearing range goes up to about 45 kHz.

#### dav2008

Gold Member
Yea, so the other one will either be 23.5+5 or 23.5-5

The beat frequency is the difference between the two whistles..so if one is at 23.5kHz and the beat frequency is 5kHz, then the second whistle will either be 5kHz lower or higher than whistle 1

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