The distinctive voices of radio broadcasters may be a result of their vocal cords being more elastic, say Australian researchers.
The suggestion follows a new study that found the vocal cords of such radio performers close faster than others.
The researchers filmed the vocal cords of 16 male radio announcers, broadcasters, newsreaders and voice-over artists using a high-speed video camera. They hoped to find out what made them sound different to non-broadcasters.
"There is an element of a radio voice that is incredibly distinctive but it's incredibly difficult to isolate and measure," said speech pathologist Dr Cate Madill, from the University of Sydney.
This quality is described in different ways in various studies, as warm, resonant, powerful, emotive, and authoritative.
Air from the lungs vibrates the vocal cords, which causes sound. This then travels through the vocal tract and out through the mouth, and to a lesser extent the nose.
The vocal tract has a particular shape and characteristics that interact with the sound to create 'resonance'. It's the resonance that gives the voice what we think of as depth, or warmth, or a 'ringing' quality.
"Some people say that to work in radio you need to be talented, or to have a voice that is fundamentally different from other voices," Madill said.
"We wanted to see if we could find any identifiable element of the anatomy of their actual vocal cords that might contribute to this phenomenon."
Filming vocal cords
The researchers placed the camera, which takes pictures at 4,000 frames per second, into the mouth to film the vocal cords as they vibrated.
"Vocal cords in men will vibrate anywhere between 100 and 120 times a second, so we need to take a lot of pictures to enable us to analyze the vibration pattern," said Madill.
The camera revealed that the closing phase of every broadcaster's vocal cords was faster than the opening phase, Madill and colleagues report in the journal PLOS ONE.
When they analyzed the video taken of 16 men who were not radio presenters, they found that the time that it took for their vocal cords to open and close was about equal.
The researchers used mathematical computer modeling to correct for elements such as loudness.
Madill inferred from the research that the vocal cords of radio presenters may have a little bit more elasticity, or that there was some manipulation of the tension in the vocal cords so that their recoil was maximized.
"However, these are just educated guesses," she said. "The vibration of the vocal cords probably makes a contribution to radio broadcasters having a warmth or depth, or an ability to maintain a particular tone whilst they move their pitch around though."
"Together with specific resonatory characteristics, it probably contributes to them being recognized as having a voice that is good for radio."
Whether someone could be trained to adjust the opening and closing speed of their vocal cords was unknown.
The researchers say female radio performers and controls were not included in the study due to limited recruitment of female radio performers and an insufficient sample size for statistical power.
Commercial versus public radio
The latest study follows on from two others by the same team. In the first they interviewed employers and educators in the radio industry an attempt to come up with a definition of what made a good radio voice.
The second study looked at the acoustic differences between radio broadcasters who worked for either public or commercial radio stations. It found that public broadcasters and non-broadcasters had voices that were slightly warmer and deeper than commercial broadcasters, who had a slightly brighter and possibly harsher resonant tone.
Madill suggests that these particular features are probably trainable.