This question is not at the right place (and down-voted) but for your information you may take a look on Frequency Range of Dog Hearing where you can read that:
Humans can hear sounds approximately within the frequencies of 20 Hz and 20,000 Hz
[…]
The frequency range of dog hearing is approximately 40 Hz to 60,000 Hz
Note also that:
The shape of a dog’s ear also helps it hear more proficiently.
A similar example is :
A vacuum cleaner, which merely sounds loud to us, can produce a high frequency sound which may scare dogs away
I expect that very low frequency can also scare dog (like thunderstorm sound)
You may use a spectrum analyser software (open source audio-software like Audacity allow you to do the job) to double check if low/high frequency are present in the sound.
In my opinion you may use a Band-pass filter, to cut all frequency lower than 50KHz & higher than 15KHz to avoid the “the vacuum cleaner” and “thunderstorm sound” effect (which may scare dogs.)
You may finally take a look on the Audacity low pass filter manual to know how to apply this filter on your sound.
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solved why do these sounds make a dog unhappy?