Supergalactic sub-subwoofer

A Scientific American article of March 2007 titled "Black Hole Blowback" by
Tucker, Tananbaum and Fabian explains how enormous jets of gas hundreds of
thousands of light-years long projected from the poles of a supermassive
black hole as large as the solar system with an energy equalling 100 million
supernovae rupture and send ripples of sound waves across the immense 10
million light-years wide nebular space:

http://chandra.harvard.edu/photo/2003/perseus/

http://chandra.harvard.edu/photo/2003/perseus/perseus_ripple_illustration.jp
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The multi-million year cosmic cycle of the life of a cluster of galaxies
numbering a thousand is staggering. As x-ray emissions cool the enormous
bubble of intergalactic hot gas, the cluster gradually begins to collapse
unto a large central galaxy. This process not only forms millions of new
stars, but also creates an accretion disk that feeds the black hole at the
core. Once fed, the monster revs up like a motor, transforming rotational
motion into linear motion, and spews forth one unit of gas for every three
it swallows. The jet is launched at the speed of light, punctures the
cluster, and creates hour-glass shaped cavities filled with intense magnetic
fields, protons, and electrons. Blasts of shock-waves are sent therefrom in
every direction which ever so gently halt the "cooling flow". As though
biting the hand that feeds, the black hole eventually chokes its supply of
gas and goes dormant, until the collapse resumes and the cycle repeats.

In the Perseus cluster, waves of sound propagate through a medium the
density of which is a few thousand hydrogen atoms per cubic meter with a
speed of 1170 km/s, and produce a pitch that is a B-flat 57 octaves below
middle C.

Clusters observed to be in possession of similar attributes are Virgo,
Hydra, MS 0735, and others.

Oz.