The oval design of an ancient Roman amphitheater in southern Spain helped voices travel across its gladiator arena and toward nearby spectator seats, according to new research. Sound tests at the ruins of Italica suggest the building’s shape directed acoustic energy to certain spots, helping people hear speech more clearly.
The effect was strongest near the arena and its front seating, where reflected sound reinforced frequencies important for understanding words. The researchers also found that sound did not spread evenly, and some positions produced echoes that could interfere with speech.
Researchers Sara Girón and Manuel Martín-Castizo of the University of Seville published their findings in the journal Heritage. They examined an amphitheater built under Emperor Hadrian in the second century, near present-day Seville. It held about 35,000 spectators and was the largest of its kind in Roman Hispania.
How ancient Roman amphitheater design carried voices across a gladiator arena
The team placed a loudspeaker at three positions in the arena and microphones at 17 points around the arena and surviving seating. The measurements captured how sound moved and bounced through the open-air structure.
Across 49 speaker-microphone combinations, the researchers traced sound reflections shaped by the venue’s oval plan. Unlike a circle, the oval directs some sound toward particular focal areas. Microphones on the first seating level recorded especially balanced sound at frequencies important for speech.
An analysis found that about 79% of measured sound energy at key frequencies arrived within 50 milliseconds of the direct sound, a pattern linked to clear words. The average speech transmission score was 0.71, with intelligibility rated “good” to “excellent” at most listening points. Clarity generally declined at distances greater than 30 meters (98 feet).
The researchers found that surviving walls and seating gave sound a modest boost compared with an unobstructed open space.
Echoes and lost seating complicate the picture
But when the loudspeaker was near the eastern focus of the oval, measurements indicated a risk of distracting echoes at six of the 49 tested combinations.
The study also compared the amphitheater with Italica’s nearby Roman theater. Both spaces generally supported spoken performances better than music, but the theater produced stronger sound overall. The amphitheater’s measured characteristics fell outside recommended ranges for symphonic music.
Researchers cautioned that modern ruins cannot fully represent the building’s original acoustics. Much of the upper seating has been lost, changing the surfaces that once reflected sound. The measurements were also carried out without spectators.
The researchers say documenting sound is part of preserving the site. Their measurements could guide temporary cultural events and future attempts to recreate the ancient arena’s acoustics.
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