The sound of a little girl blowing a raspberry was the sweetest Moira Kelly has ever heard.

Krishna, the second conjoined twin separated from her sister in a marathon operation last week, finally awoke from her medically induced coma on Friday night and made the signature sound her guardian has been waiting for.

Ms Kelly, the guardian of the Bangladeshi twins, had always said that the sound of Krishna blowing a raspberry would be her personal sign that the toddler had pulled through the surgery to separate her from her twin Trishna

She got that sign three days after the 32-hour operation to separate the twins' skulls, and more than 24 hours after Trishna, the stronger of the twins, had woken.

"Krishna has woken up and I got my raspberry,'' a jubilant Ms Kelly told reporters outside the Melbourne Royal Children's Hospital, where the lifesaving surgery was performed on Monday. The first raspberry was followed by seven more in quick succession, she said.

The twins, who were rescued from an orphanage in Bangladesh two years ago and taken to Australia for the life-saving surgery, were connected at the top of their skulls and shared blood vessels and brain tissue. The operation to separate them was the culmination of a two-year schedule of procedures which include five other operations, including a 20-hour session to separate the blood vessels.

Trishna woke up on Thursday and was soon talking and cuddling Ms Kelly, but Krishna's body had more to adjust to and she spent longer recovering under sedation.

Ms Kelly,from the Children First Foundation charity which brought the twins to Australia, said she ``did a big yelp'' when Krishna blew the raspberries.

She then rang members of the medical team who performed the groundbreaking surgery to tell them the good news.

"The whole hospital is smiling," Ms Kelly said. "I didn't have that smile until the raspberry arrived."

MRI brain scans show neither child has suffered brain damage, but they still have a mountain to climb in their new, separate lives. The girls, who turn three next month, will have intensive physiotherapy to learn how to balance and sit up, and the physical challenges they face will be equalled by the psychological challenge of getting to know each other as individuals.

Staff at the Royal Children's Hospital have kept the twins' cots as close together as possible as they recovered from their surgery and now the girls are both awake they plan to push the cots together so they can touch each other.

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