Analysts are predicting "significant growth" in the adoption of satellite and HD radio over the next five years.

A report from Parks Associates suggests that satellite radio subscribers will increase from 20.5 million in 2008 to 39 million by 2012.

High-definition radio adoption will also increase, growing from 4.2 million in 2008 to 30 million by 2012.

"The XM and Sirius merger, the emergence of HD radio, and the availability of online offerings will create new listening experiences for consumers," said Chris Roden, a research analyst at Parks Associates.

"To ensure future success, providers must align their products and services with the expectations and demands of the consumer."

Roden added that a majority of satellite radio owners are attracted by the portability of the service, particularly while driving.

"Conversely, HD radio owners view the product as similar to other consumer electronics devices, such as DVD players and home networks, and are more likely to listen to the service at home."

• Parks Associates Report: Music to Consumers' Ears: Next Generation Radio (PDF)