Just like a musical instrument, the length, diameter, plenum effects, and size, frequency, duration, and pressure of pulses of gas going through a series of tubes that make up an engine can produce magical sounds.
The accidental combination in Edward Turner’s Triumph Speed Twin motorcycle engine of 1937 in all its variations is one pinnacle of musical perfection through acoustic serendipity, but the supreme example for me is the Avro Vulcan bomber. The intake geometry and ducting designed by a team led by Roy Chadwick (who also designed the WWI Avro 504 and WWII Lancaster) and the Bristol/Siddeley/Rolls Royce Olympus engine literally made the earth move during low passes, with a sweet spot at wide throttle openings that produced turbulence vortices in the intakes for a sustained high frequency accompaniment.
I was privileged to attend Mildenhall US airbase in Suffolk's ‘hearts and minds’ open day for local residents in 1978. Two Vulcan bombers did synchronised aerobatic displays over the crowd, which culminated in them each coasting along just over the runway with the throttles barely open and making a low whistling noise, then going to full power and rocketing up at a steep angle, giving a deafening droning howl from the intakes at the same time as producing enough low frequency sound to not only make the ground shake, but also cause my diaphragm to vibrate in sympathy.
They were also there for 1982, when the open day had become a public airshow. An SR-71 Blackbird, the first stealth aircraft, that flew at 3 times the speed of sound, flew in from Beale AFB, Calif, made a rolling touchdown along the runway, and then shot up vertically on top of a blue flame about 20 feet long, disappearing from sight almost too fast for the eye to follow.
But it wasn’t as loud as a Vulcan.
Listen here (don’t forget to turn the sound on: loudspeaker icon lower right).
Photo © M.Fisher
