Rife actually used both. Most of the publically available copies of the surviving laboratory notes of Rife himself show frequencies in the radio frequency ranges, so on that basis some people claim that Rife used only radio frequencies.
This is not true for at least three known reasons. Firstly at least one of the surviving lab notes shows a frequency in the audio range. Secondly analysis of machines produced by the Beam Ray corporation and which were actively promoted by Rife used mainly audio frequencies. Lastly, according to Dr James Couche who worked with Rife in the treatment of cancer patients at the famous Scripps Ranch trial, Rife was using frequencies in the audio range.
Rife teamed up with John Crane in the 1950's onwards. Crane produced machines and frequency lists that show audio frequencies. Although Rife was less active in this work, there is circumstantial evidence that indicates that he knew audio frequencies were being used and he did not apparently make any objection. On that basis it's reasonable to assume that even if Rife did not specifically endorse audio frequencies he did not object to their use either.
Modern derivations of his work mostly use audio frequencies as Crane did and these devices tend to show beneficial bioactive effects. Whether they are doing exactly the same thing as all of Rife's original machines is still a point of discussion or even contention but real people are finding that audio frequencies are helping to resolve a great many health issues and so there is no reason to doubt their effectiveness.