Thank you for the opportunity to help you with your question!
Different (with almost 100% certainty)
Any unique sound is made up of a specific band of pure sine wave frequencies at specific relative amplitudes at any given time. It is highly unlikely that two different people could pronounce the word dog exactly the same. Even if they were able to produce the same band of sine wave frequencies and at the same peak amplitude during the pronunciation of the word dog the relative amplitude of some of the frequencies with respect to the peak would most likely be different.
Of course if the word dog is pronounced exactly the same by two different people then neither of the pronunciations is unique and the two frequency spectrums would be exactly the same at all corresponding times during the pronunciations.
Please let me know if you need any clarification. I'm always happy to answer your questions.