Acoustic simulation of JS Bach's Thomaskirche in 1723 and 1539

This paper investigates an early acoustical theory of Hope Bagenal about the Leipzig Thomaskirche, where J.S. Bach composed and conducted from 1723 to 1750. Bagenal predicted that the church had a shorter reverberation time than previously in Bach's time as a result of the Lutheran alterations to the space in the 16th century. This study uses on-site measurements to calibrate a geometric acoustical model of the current church. The calibrated model is then altered to account for the state of the church in 1723 and 1539. Simulations predict that the empty church in 1723 had a T30 value nearly one second lower than today, while the empty church in 1539 was much more reverberant than today. However, when the fully occupied church is simulated across all time periods, the difference in T30 is much smaller, with values at 1 kHz ranging from 2.7s in 1539, 2.5s in the present day, and 2.3s in 1723. These empirical data are crucial for understanding the historical setting of Bach's music as heard by its original congregation and by its composer.