ROMANS didn't just send people to gruesome deaths in their gladiatorial amphitheatres, they could hear every last scream, too. The acoustics of Greek and Roman amphitheatres, it seems, improved with every new design.

The open-air theatres of ancient Greece around 1500 BC were simple rectangular or trapezoidal arenas surrounded by wood or stone seating on the same level. By 500 BC, the semicircular amphitheatre began to take shape, with concentric rows of marble seats often raised on a low slope. Later, the Romans raised the stage, walled it at the back and made the seats very highly tiered.

But were these changes merely to pack in bigger crowds? To find out, Jian Kang and Kalliopi Chourmouziadou at the University of Sheffield, UK, studied how the theatres' acoustics changed through the ages (Applied Acoustics, DOI: 10.1016/j.apacoust.2006.12.009). They analysed six Greek and Roman designs using software that simulates how sound level, clarity and reverberation behave in 3D spaces.

They found that the acoustics improved as the theatres got more enclosed, had steeper seats and higher stages, and were built from harder materials. "These measures allowed for multiple sound reflections between the seats and the stage," says Kang. "This higher reverberation made it much more like an indoor space."