Echo Bridge

Bridge arches can have great echoes, this one is meant to repeat a human voice up to 15 times

1 Star, yawn2 Stars, OK3 Stars, interesting4 Stars, worth a detour5 Stars, worth a journey
(7 Votes, average 3.71)

Built in the 1870s, this large arched bridge spans the Charles River. There are steps down to a specially built listening platform so you can hear the sound effect. In September 1948, Arthur Taber Jones wrote to the Journal of the Acoustical Society of America, detailing a small study. ‘A handlcapp [sic] is returned in a series of about a dozen echoes of decreasing loudness, and at a rate of about four echoes per second.’ [1]

By Daderot – Own work, CC0

The question Jones posed in his article was whether the sound was skimming around the inside of the curved arch, like a whispering gallery or propagating horizontally just above the water. The video below, created with a modern acoustic prediction model shows how sound moves under the bridge. No wonder Jones struggled to work out what was going on, because it seems that the sound both skims around the arch and bounces back and forth horizontally just above the water.

While Echo Bridge is unique in having been a subject of scientific study, I’ve found that other arched railway and canal bridges have the same sound effect once you know the general shape to look out for.


A Walking Tour of Hemlock Gorge (including a visit to the echo platform). The bridge spans the Charles River between Needham and Newton.


Thanks to Jonathan Sheaffer for modelling the sound propagation.
[1] A. T. Jones, “The echoes at Echo Bridge,” J. Acoust. Soc. Am. 20, 706-707 (1948).

Author: Trevor Cox

I am a Professor of Acoustic Engineering at the University of Salford where I carry out research and teaching focussing on architectural acoustics, signal processing and audio perception. I am also an author and radio broadcaster having presented many documentaries on BBC radio and written books for academics and the general public.