Sounds from an Impractical Homemade Engine

  • Playlist
  • Download
  • Embed
    Embed <iframe src="" width="100%" height="290" frameborder="0" scrolling="no">
  • Transcript

Our SoundClip series continues with listener Larry Cottrill, who provides audio of a homemade pulse jet engine. It's very loud and very simple, and it can't be muffled. Therefore, it is impractical despite its efficiency.


Today's sound clip is about something very simple and very loud.

Mr. LARRY COTTRILL: (Pulsejet Hobbyist) My name is Larry Cottrill. I live in rural Mingo, Iowa. The sound I'm going to share today is the sound of a home-built valveless pulsejet, which is a favorite hobby of mine.

(Soundbite of pulsejet engine starting up)

Mr. COTTRILL: The valveless pulsejet is fascinating to me for several reasons. The engine can occur in many different forms, many shapes and sizes. And all of them, though, are just basically a specially shaped and very carefully shaped hollowed metal tube.

Now, these things had no precision machining. There are no moving parts at all. There's no lubrication. There's nothing that needs any ongoing maintenance. A frequent question about these engines that people ask is why aren't big examples of these designs in everyday use for things, because you have an engine that requires no maintenance, has no moving parts and so on. And the basic reason they aren't used is because of the engine's sound.

(Soundbite of pulsejet engine)

Mr. COTTRILL: These engines are very, very loud. The starting of engine often involves noisy pops and bangs and a very disconcerting noise.

(Soundbite of pulsejet engine starting)

Mr. COTTRILL: Once the engine is actually running, it's a nasty, gritting, penetrating noise. It's a very visceral, gut level kind of noise that we - pulsejet hobbyists - absolutely love.

(Soundbite of pulsejet engine)

Mr. COTTRILL: What you just heard is the sound of the simplest jet propulsion ever devised. The valveless pulsejet engine.

SIEGEL: That sound clip from listener Larry Cottrill of Mingo, Iowa.

(Soundbite of pulsejet engine)

Copyright © 2007 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR’s programming is the audio.



Please keep your community civil. All comments must follow the Community rules and terms of use, and will be moderated prior to posting. NPR reserves the right to use the comments we receive, in whole or in part, and to use the commenter's name and location, in any medium. See also the Terms of Use, Privacy Policy and Community FAQ.