The pronunciation of the character "He" added with the "Nian" sound is "hē nián." This combination is commonly used in Chinese to express the phrase "年"，which means "year" in English. The character "He" is pronounced as "hē" when combined with the "Nian" sound, and it retains its original tone, which is a level 1 tone.

The reason for this pronunciation lies in the rules of Chinese phonetics. In Mandarin Chinese, characters are often pronounced based on their tone and the combination of consonants and vowels. The character "He" (汉字) is pronounced "hē" with a level 1 tone, which is a high, level tone. When combined with the "Nian" sound, the character "He" maintains its original pronunciation, and the "Nian" sound does not alter the tone of the character. This is because the "Nian" sound is simply an additional syllable that is appended to the character "He," and it does not change the character's inherent pronunciation.

According to the "Pinyin" system, which is the standardized romanization of Chinese, the character "He" is romanized as "hē," and the "Nian" sound is romanized as "nián." The "Pinyin" system is widely used in China and internationally for the learning and teaching of Mandarin Chinese. The pronunciation of "hē nián" is consistent with the "Pinyin" romanization, further reinforcing the accuracy of this pronunciation.

Data from the "Pinyin" system and linguistic studies support the pronunciation of "hē nián" for the character "He" added with the "Nian" sound. The "Pinyin" system has been in use since 1958 and is the official romanization system for Chinese. It is based on the standard pronunciation of Mandarin Chinese, which is the official language of China. Linguistic studies have also confirmed the pronunciation patterns in Mandarin Chinese, including the preservation of the original tone of a character when combined with another syllable.

In conclusion, the pronunciation of the character "He" added with the "Nian" sound is "hē nián," which is consistent with the "Pinyin" system and linguistic studies. This pronunciation is essential for accurate communication in Mandarin Chinese and is widely recognized and used in both China and the international community.