As David Bordwell describes, technological improvements continued at a swift pace: "Between 1932 and 1935, Electric and RCA created directional microphones, increased the frequency range of film recording, reduced ground noise ... and extended the volume range." These technical advances often meant new aesthetic opportunities: "Increasing the fidelity of recording ... heightened the dramatic possibilities of vocal timbre, pitch, and loudness." Another basic problem—famously spoofed in the 1952 film "Singin' in the Rain"—was that some silent-era actors simply did not have attractive voices; though this issue was frequently overstated, there were related concerns about general vocal quality and the casting of performers for their dramatic skills in roles also requiring singing talent beyond their own. By 1935, rerecording of vocals by the original or different actors in postproduction, a process known as "looping", had become practical. The ultraviolet recording system introduced by RCA in 1936 improved the reproduction of sibilants and high notes.