The word "blattered" is not a commonly used word and is not found in many dictionaries. However, if we were to assume that it is a variation of the word "blathered", it would be spelled with a voiced "th" sound, represented by the IPA symbol /ð/. This sound is often mispronounced as an unvoiced "th" sound (/θ/), which can lead to misspellings such as "blattered". Therefore, it is important to pay attention to the voiced or unvoiced pronunciation of the "th" sound when spelling words that include it.