The big cats' vocal cards have an odd square shape that allows them to withstand strong stretching and shearing, researchers say in a study published in the online journal PLoS ONE.
University of Utah researcher Tobias Riede says that shape "makes it easier for the tissue to respond to the passing airflow," allowing louder roars at lower lung pressure.
It had previously been thought lions roar deeply because the vocal folds are heavy with fat, but the new study suggests the fat gives the vocal folds their square shape as opposed to the more traditional triangular vocal folds found in most species, and may cushion the vocal folds and provide repair material when they are damaged.
The findings could have application to human voice problems, the researchers said.
"If you understand how vocal folds are structured and what effects that structure has on vocal production, then it could help doctors make decisions on how to reconstruct damaged vocal fold tissue" in people such as cancer patients, singers, teachers, coaches and drill sergeants, Riede says.