Acoustic Simulation of Julius Caesar’s Battlefield Speeches

Braxton Boren

doi:10.3390/acoustics1010002

Abstract

History contains many accounts of speeches given by civic and military leaders before large crowds prior to the invention of electronic amplification. Historians have debated the historical accuracy of these accounts, often making some reference to acoustics, either supporting or refuting the accounts, but without any numerical justification. The field of digital humanities, and more specifically archaeoacoustics, seeks to use computational techniques to provide empirical data to improve historical analysis. Julius Caesar recalled giving speeches to 14,000 men after the battle of Dyrrachium and another to 22,000 men before the battle of Pharsalus during the Roman Civil War. Caesar’s background and education are discussed, including his training in rhetoric and oratory, which would have affected his articulation and effective sound pressure level while addressing his troops. Based on subjective reports about Caesar’s oratorical abilities, his effective Sound Pressure Level (SPL) is assumed to be 80 dBA, about 6 dB above the average loud speaking voice but lower than that of the loudest trained actors and singers. Simulations show that for reasonable background noise conditions Caesar could have been heard intelligibly by 14,000 soldiers in a quiet, controlled environment as in the speech at Dyrrachium. In contrast, even granting generous acoustic and geometric conditions, Caesar could not have been heard by more than about 700 soldiers while his army was on the march before the battle of Pharsalus.

Highlights

Throughout most of human history, electronic amplification of the spoken word was unavailable; all human gatherings were effectively limited in size by the acoustic range over which the person speaking could be heard intelligibly
This paper examines the historicity of these accounts through archaeoacoustic simulations of the speeches as Caesar describes them
It can be shown that, even without every historical detail preserved exactly, the plausibility or implausibility of certain historical speeches may be known with a high degree of certainty once we examine the acoustical evidence

Summary

Introduction

Throughout most of human history, electronic amplification of the spoken word was unavailable; all human gatherings were effectively limited in size by the acoustic range over which the person speaking could be heard intelligibly. Hansen made many historical and textual arguments that need not be reproduced here in detail, but among these, he made acoustical claims, such as the area over which an ancient phalanx stretched, or noise from rattling hoplite armor, leading him to conclude that Under such circumstances it must have been impossible for a general, even if he had had the voice of a Stentor, to deliver a speech that could be heard by all the soldiers simultaneously [6]. Kendrick Pritchett replied with a 100-page rejoinder defending the authenticity of the general’s harangue, listing in detail different accounts of speeches to large crowds from ancient Greece and Rome, and including more recent accounts, from Henry V at Agincourt to George Washington [7] Pritchett mentioned these military examples as well as another from the preacher John Wesley, arguing that it is acoustically possible for a single speaker to reach such a large assembly. Caesar, who was with his men as they were about to march out of the gate in formation, said to them, “We need to put off our march for and turn our thoughts to battle, which is what we have been demanding all this time

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