Brian Posted June 11, 2004 Share Posted June 11, 2004 I've just found a 1964 technical paper talking about air-powered loudspeakers. Basically a flow of air, 40psi at 500cu ft/min, is modulated by a small (100w) electromagnetic driver and coupled to a horn with a 12ft x 12ft mouth. They were designed to do propagation testing on the noise generated by a Saturn rocket ;) A Saturn rocket generates noise at 120dB at 1 mile over a 1Hz to 500Hz bandwidth. This equates to 50 million acoustics watts :** laughs out loud **: The air speaker in the paper could only generate 2000 acoustic watts, up to about 100Hz, but remember that a 100W loudspeaker does not generate 100 acoustic watts, it only generate around 1 acoustic watt becuase they are not 100% efficient. So one of these air powered speakers, as a sub, would be equivalent to around 200kW of normal speakers! And the paper goes on to talk about designing units that will generate between 25,000 and 100,000 acoustic watts ie 2.5 Megawatts or more of conventional speakers. Link to comment Share on other sites More sharing options...
Drew Posted June 11, 2004 Share Posted June 11, 2004 That is very very loud. I said "###### me" when reading it, which got odd looks in the computer room! Link to comment Share on other sites More sharing options...
Lamplighter Posted June 11, 2004 Share Posted June 11, 2004 An exponential horn is around 10 % efficient, one with a 6 ft bell was regularly used as a demonstration using a National Health Service deaf aid earpiece as the driver, with a rolled up sheet of newspaper to provide the taper from earpiece to horn. The source was a small transistor radio approx 100mW output and the resultant sound easily filled a 500 seater hall with band music. After that I cannot begin to imagine the effect of 2Kw acoustic. ( I think the demonstration above was by the late Harold Leak) Brian ps I cant find an Emoticon with fingers in ears! Link to comment Share on other sites More sharing options...
PeterT Posted June 11, 2004 Share Posted June 11, 2004 Slightly :) I remember there was a Clarkson Telly program about Nasa in Florida setting up a PA system to mimic the sound level of a Shuttle rocket being fired. They then drove trucks in all four directions away from the noise until it reached an acceptable level (about 20 Miles!) and then they bought the land in between. They now use that land to test their rocket motors and half an hour after they've done the test it rains...Yes Ladies and Gentlemen Nasa in fact now make weather! Link to comment Share on other sites More sharing options...
Andrew C Posted June 12, 2004 Share Posted June 12, 2004 In 1972 or so I saw (& heard) a Saturn 1b launch. The 1b is about as big as the top 2 stages of the Saturn 5, and was used to take crews up to Skylab. The noise was such that even at a distance of miles my chest was resonating.To get some idea of the volume, imagine standing at the end of a runway with Concorde (RIP) taking off just overhead. Truly, truly awesome. Link to comment Share on other sites More sharing options...
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