Michael Eskin Posted September 29, 2004 Share Posted September 29, 2004 (edited) For weeks I've been trying to figure out why my lovely Tedrow 30 key anglo sounds perfectly in tune at home, but horribly out of tune at the pub... It dawned on me tonight that there's a ceiling fan over where we hold the session, and I'm getting a beating effect of the fan against the tone, probably combined with some kind of doppler shift on the reflections. I'd run into this same acoustic effect while staying with family on a recent vacation. Their guest room had a ceiling fan that caused the same nasty effect, but it took me a couple of months to realize, duh, there's also a fan above the session, its not me or the instrument. Mystery solved! Interestingly, it doesn't effect flutes, whistles, Uilleann pipes or fiddles nearly as much as concertinas... Edited September 29, 2004 by eskin Link to comment Share on other sites More sharing options...
JimLucas Posted September 29, 2004 Share Posted September 29, 2004 It dawned on me tonight that there's a ceiling fan over where we hold the session,... Yep. This problem is discovered independently by someone else every few months. There have even been some intriguing technical debates (in forums other than Concertina.net, as I recall) as to whether it's a frequency-shifting Doppler effect or something else. Link to comment Share on other sites More sharing options...
Chris Timson Posted September 29, 2004 Share Posted September 29, 2004 Yep. This problem is discovered independently by someone else every few months. Perhaps I need to add an FDP section to the FAQ (that's Frequently Discovered Problems). Chris PS I think I will find some way of getting it in the FAQ. It is such a disconcerting effect when you encounter it for the first time. At home I get a clear vibrato when the ceiling fan is on in the neighbouring room. Link to comment Share on other sites More sharing options...
geoffwright Posted September 29, 2004 Share Posted September 29, 2004 Anything to do with air-temperature? Or trying to suck moving air into the box causing low/fluctuating air pressure? Link to comment Share on other sites More sharing options...
synchopepper Posted September 29, 2004 Share Posted September 29, 2004 I have also noticed this fan affect and find that it is much more pronounced with my concertina that with my banjo or guitar. I think the reason is that the note decays much faster when a string is plucked that the sustained note of a reed making the phenomena harder to define. I do find the perceived degradation in sound simular for plucked strings even if it is harder to figure out why. I surmise the fluctuation of the echos returning to the player's ear are averaged out by the brain and have the effect of changing the perceived pitch slightly. (how's that for off-the-cuff BS?) Link to comment Share on other sites More sharing options...
premo Posted September 29, 2004 Share Posted September 29, 2004 Intriguing Does the speed of the fan affect the effect? Do you have to be right under the fan or just near it? Does the pitch go up/blade, down/gap or down/blade, up/gap? Link to comment Share on other sites More sharing options...
JimLucas Posted September 29, 2004 Share Posted September 29, 2004 (edited) how's that for off-the-cuff BS? A pretty good description. Does the pitch go up/blade, down/gap or down/blade, up/gap? Neither one, in my experience. I don't perceive it as a pitch change. Nor would I expect one. The common assumption of a Doppler effect is contrary to physics: ... The Doppler effect on perceived pitch is not caused by something simply moving, but due to a continuously changing distance between the sound source and the listener, usually caused by motion of the one toward or away from the other. The fan is moving, but neither toward nor away from either the concertina or the listener. Furthermore, if it were a Doppler effect, it should affect flutes and fiddles just as strongly as concertinas, but it seems not to. I have my own theories as to what causes the effect, but so far they're just theories. For all the discussion this effect has generated over the years, I'm not aware of any research that has determined -- or even rigorously tried to determine -- the real cause. So rather than engage in speculation, I prefer to just say that, "We really don't know the cause, but please turn off the fan." Edited September 29, 2004 by JimLucas Link to comment Share on other sites More sharing options...
Daniel Bradbury Posted September 29, 2004 Share Posted September 29, 2004 And I thought all along that I had a Hammond B3 concertina..... Link to comment Share on other sites More sharing options...
megmcd Posted September 30, 2004 Share Posted September 30, 2004 I've noticed that when I try to play my Dipper while I'm a car passenger, the concertina sounds and feels odd if the car fan is on, especially if the air conditioning is running. The concertina sounds hoarse and dry. (I suspect of course that my dear husband has figured out this is how to stop my playing while he's trying to drive! Although the alternative, my playing while I drive, is obviously worse.) Might this be related to the ceiling fan effect? Link to comment Share on other sites More sharing options...
David Barnert Posted September 30, 2004 Share Posted September 30, 2004 It also affects accordions but not recorders, fiddles, guitars, or any other non-free reed instrument I've noticed. This leads me to suspect that it has to do with the physics of free reed vibration rather than the Doppler effect (which would affect any sound wave). My guess (but I found no takers when I mentioned this in the old forum) has to do with fluctuations in air pressure at the reed. But Jim is right: until someone studies it scientifically, we're all just guessing. I have more than once stopped a talent show when I saw a concertina player take the stage and sit down under a spinning ceiling fan. A thankless job (unless you hear the phenomenon, you don't want to believe it) but somebody has to do it. Link to comment Share on other sites More sharing options...
JimLucas Posted September 30, 2004 Share Posted September 30, 2004 Might this be related to the ceiling fan effect? Absolutely! What matters is that it's a fan, not that it's on the ceiling. Link to comment Share on other sites More sharing options...
Peter Stephenson Posted September 30, 2004 Share Posted September 30, 2004 Will the fluttering be affected by the distance the fan is below the ceiling ? if so it could be the note is partially reflected off a blade and partially off the ceiling, same as driving past a fence with the window down. Link to comment Share on other sites More sharing options...
geoffwright Posted September 30, 2004 Share Posted September 30, 2004 Can anyone in the next room hear the same effect, (or in a distant corner of the room) or is the effect limited to people sat under the fan? Link to comment Share on other sites More sharing options...
JimLucas Posted September 30, 2004 Share Posted September 30, 2004 Will the fluttering be affected by the distance the fan is below the ceiling ? I don't know about "affected by", but I've experienced the effect with a window fan in an open window (i.e., no ceiling or wall behind it). And I repeat, if it were an effect of the fan blades on the sound, it should also affect flutes and fiddles, but it seems not to. So I agree with David B., it has to be something that affects the way the instrument makes the sound, something which affects concertinas, but not flutes and fiddles. Can anyone in the next room hear the same effect, (or in a distant corner of the room)... Yep. That's why David said he had to interrupt when a performer sat beneath a fan. The entire audience will hear the awful din and think that concertinas sound like that. [P.S. I'm not going to re-ignite that other thread this time around, but this is my post no. 2200. ] Link to comment Share on other sites More sharing options...
Ed Stander Posted October 1, 2004 Share Posted October 1, 2004 C'mon people, don't you remember the '60's? You take a hammond organ, and place a fan in front of the speaker and you get a Leslie Organ and sell millions of copies of your acid rock music. I think psychodelic concertina may be the wave of the future. Enough folk music already! Link to comment Share on other sites More sharing options...
Chris Timson Posted October 2, 2004 Share Posted October 2, 2004 Enough folk music already! I'm sorry, that's not physically possible, is it? Chris Link to comment Share on other sites More sharing options...
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