Can You Hear Me at the Back

Acoustic amplification in early theatre

The Greek and Roman theatres were large, to accommodate many people on stage and in the audience. Physics and mathematics played a significant role in their design, to modify the acoustics so the actors' voices could be heard everywhere.

Theatre of Epidauros

It is probable that Pythagoras (Q30510) was the first person to research sound and acoustics, in the 6th century BCE. He noticed that, unlike light, sound does not always travel in straight lines, and began to understand reflection and absorption. He observed that the sound of the chorus changed if the floor of the theatre was made of a soft mixture of sand, straw and chaff, rather than hard, flat sand.

Theatre Mask (Tragedy), from the 4th/3rd century BCE

In the 1st century BCE, Marcus Vitruvius Pollio (Q467) wrote his books De Architectura (Q466), including detailed instructions for building theatres with good acoustics. Crediting earlier Greek sources, he wrote,

Therefore the ancient architects following nature’s footsteps, traced the voice as it rose, and carried out the ascent of the theatre seats. By the rules of mathematics and the method of music, they sought to make the voices from the stage rise more clearly and sweetly to the spectators’ ears. For just as organs which have bronze plates or horn sounding boards are brought to the clear sound of string instruments, so by the arrangement of theatres in accordance with the science of harmony, the ancients increased the power of the voice.

Vitruvius identified specific acoustic effects in theatres caused by reflections, both wanted and unwanted, including ‘consonant places’ where the voice ‘falls on the ear with great distinctness of words. Hence, if due care be taken in the choice of the situation, the effect of the voice will be improved and the utility of the theatre increased’.

Sounding vessel from a church in the Netherlands

Sounding vessel from a church in the Netherlands

Sounding vessel from a church in the Netherlands

In antiquity, the design of the theatre significantly impacted how the sound was going to be received by the audience. Starting around 500 BC and usually set into the side of a hill, theatres had semi-circular tiered seating on the slope, curving around the stage – for example, the theatre in Epidaurus (Q7830), finalised in the late 4th Century BCE. The largest of the Greek and Roman theatres placed the furthest audience member around 50m from the performers, a much greater distance than more recent theatres and opera houses. Modern day studies suggest, however, that 40m is a maximum distance for words to be clearly understood, and that is if the audience is already familiar with the play.

Several techniques were used to help the audience follow the drama. Words were often repeated, and possibly directed to different parts of the auditorium. A wooden wall behind the stage began to be added – the skene – to reflect the sound towards the audience. This wall could be painted with a scene appropriate to the action, and developed into a more permanent architectural structure that could house dressing rooms.

It has been suggested that a way of amplifying the voice was through the use of the mask. These masks were conical in the shape of a mouth and fitted on the head like a helmet. The conical part may have allowed the voice to be amplified so the sound reached the audience at the back. Without this design the masks would limit and muffle the actors’ voices. Other sources state that masks had no benefit for intelligibility, but were purely so actors could play multiple roles.

Another possible means of amplifying the sound was the acoustic jar, also known by the Greek name echea (literally ‘echoers’), or sounding vases, ceramic vessels set under the seats. They are believed to have been intended to improve the sound of singing, and were supposedly used to enhance the voices of performers, though no archaeological evidence has been found. The vessels mentioned by Vitruvius are made of bronze and designed specifically for each theatre. They used mathematical calculations to decide where they should be placed with a ‘due regard to the laws and harmony of physics’. No original examples survive from the ancient world. Modern experiments have indicated that their effect would have been to absorb certain frequencies (acting as a Helmholtz resonator), rather than to amplify sound – an application found in many buildings since, and used today in recording studios to control unwanted resonances.

In modern times, in a city park in Syracuse, Italy, artist Michele Spanghero built the Echea Aeolica in 2015, a fibreglass and steel sound sculpture ‘to create a connection to the ancient history of the land as if it leads an echo from afar’.