The man recorded giving instructions to the attackers used a few Hindi words an Urdu speaker would not use, such as "prashasan" for "administration," officials said. The Urdu word would be "intizamiya."
Investigators have sent the voice samples to a lab for further analysis, newspaper reports said.
Saudi Arabia's decision to hand Ansari over to India, rather than Pakistan, appeared to surprise Indian officials. Saudi Arabia and Pakistan have long held close ties.
Foreign Ministry spokesman Syed Akbaruddin described the arrest as something "rather new" in Saudi-Indian relations. "Our relationship with Saudi Arabia is expanding in a variety of ways."
Analysts said Riyadh's decision marked a significant shift.
"It is a signal to Pakistan that it will get isolated if it thinks state sponsorship of terrorism can be a viable policy option," said Ajit Doval, former chief of India's Intelligence Bureau.
Image: Pakistan's Interior Ministry chief Rehman Malik recently dismissed assertions by Indian leaders, including Chidambaram, that Pakistani state and non-state actors were involved in the Mumbai attacks and stoutly defended the ISI as an 'elite agency'.