The female voice was indeed mispronouncing the word Bett. I've disabled it, so hopefully you only hear the male voice for this sentence from now on, which pronounces it correctly.
I don't think it worked. I just got the female voice, and the pronunciation is still bad (sounded like "bait-t").
To illustrate this:
"das" is an article in: Ich habe das Bett und du hast das Sofa. *(Only 1 bed in the room)
"das" is a demostrative pronoun in: Ich habe das Bett hier und du kannst dir eines von den anderen aussuchen. (Several beds in the room)
Because of the difference between "a" and "the". They have a different meaning in English and also in German:
"A bed" is any bed.
"The bed" is a specific bed.
"A" is called the indefinite article.
"The" is called the definite article.
In German the indefinite article is ein- (i.e. ein/eine/einen/etc.) and the definite article is der/die/das/etc. For each, the ending is affected by the gender, plurality and case.
This sentence has the definite article das for the singular neuter noun Bett in accusative case. It translates as "the". If it was going to translate as "a bed", it would have to be ein Bett in this sentence.
Why is "I have this bed" wrong?? It's the second option that Duo gave us FFS!
Would this be how it's phrased in German if, for instance, you're claiming the bed in the room so that your companion has to use the sofa?
No, Bett is a neuter noun. Using den in such a sentence would be for masculine nouns.