Varying wildly in acoustic range, new research shows human screams are pretty unique when compared with those of other species.
In what sounds like the start of a horror movie, scientists have undertaken a new study to help unlock the secrets of human screams. Presenting their findings at the Acoustical Society of America meeting today (15 May), researchers from Emory University subjected people to various human sounds and screams.
A total of 181 volunteers listened to 75 vocal sounds, representing a broad acoustical range and array of emotional contexts, and were asked to say whether it was a scream or not a scream.
To determine what qualities make sounds more scream-like, the researchers analysed the sounds with respect to 28 acoustic parameters that assess pitch, timbre, duration, frequency range and roughness.
“Rough sounds are perceived as harsh, raspy, gravelly or buzzing. Some recent research has suggested that roughness might be a defining quality of screams, so one of our goals was to assess this idea,” said researcher Jay W Schwartz.
After running the experiment, the researchers found that sounds often classified as screams showed certain acoustic factors, including a high and sweeping/arcing pitch, as well as high roughness. Strangely, however, they also found that one decidedly non-scream sound – a whistle – was labelled as a scream by 71pc of the study’s participants.
“This made sense though when we looked into the acoustic qualities of the whistle,” Schwartz said. They found it exhibited many of the traits to be associated with screams, such as a high and arcing pitch, and moderate-high roughness.
Also surprising was that the vocalisations people labelled as screams came from a wide range of emotional contexts. “Some were fearful, while others were angry, surprised or even excited,” Schwartz said. “In almost all other species, screams are reserved for a particular situation, like an attack by a predator or rival.”
With the findings showing that few screams sound the same, the researchers now want to see if humans use different-sounding screams in different situations. Schwartz’s fellow researcher, Harold Gouzoules, said they will analyse screams using functional MRI to look at what’s happening in the brain when we scream.
“Screams are inherently interesting vocalisations but there are also potential human health applications of research on screams as there are multiple psychiatric disorders that involve screaming behaviour,” Gouzoules said.