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(I've played a sine wave on my laptop before for only 10 seconds. The internal speakers broke. I got new for free because they thought it was a guarantee case. I did it again for 5 seconds, and I noticed that it smelled bad, so I realized that my speakers didn't handle it and turned it off before it was too late.)

Can I safely play a sine wave (regardless of volume) on our local church's PA system? (The volume I intend to use when playing it is NOT louder than what we play when we play music.) Will a sine wave do more damage to the ears at the same volume than music does? (Because of the resonance.)

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Whether it its a sine wave or not is almost irrelevant. I say almost, as if you do hit a resonant frequency you could destroy something else in the room - theoretically... you would need power to do this though.

You did not destroy your laptop speakers because you played a sine wave. You may have destroyed them because the volume was too high or there was a fault.

In reality, you are less likely to damage a speaker using a sine wave as you will have less rapid transitions than a sound of the same frequency with harmonics and other higher frequencies. A sine wave is actually the most gentle of movements for a speaker.

Have a look at this image from wikipedia. For a speaker to follow a sine wave - the top waveform - it just moves in and out with the sine wave, but to try and match the square wave - the second waveform - it has to move incredibly fast at each of those vertical transitions. This requires a lot of power in high frequencies and can very easily burn out a speaker coil, or destroy the physical cone if the speaker is not rated for those frequencies.

enter image description here

As for your question regarding playing in the church, it is all about the volume.

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Aha, strange. I can play music at full volume, even if the whole song is overly compressed. But if I play a sine wave for 5 seconds, it starts smelling smoke and burnt wire. So playing a dark sine wave for special effects will not damage the speakers, only the ears, if played too loud. –  Friend of Kim Apr 28 '12 at 22:38
    
Are your ears more vulnerable to sine waves because of the resonance? They don't need much energy to brake.. –  Friend of Kim Apr 28 '12 at 22:38
    
There is no such think as a "dark sine wave". What frequency do you think would resonate in the ears? I think you should have a look at the wikipedia pages for resonance, sine waves and similar topics. –  Rory Alsop Apr 28 '12 at 23:23
    
Hmm, well. I've just read lots of places that sine waves makes the coil in the speakers burn and the speaker is broken. –  Friend of Kim Apr 29 '12 at 7:17
    
I have looked at a wide range of audiophile sites and can't find any that say a sine wave will break the speaker. Lots of discussion about breaking-in (getting new speakers ready) using sine waves, but no damage. Can you point us at some links. –  Rory Alsop Apr 29 '12 at 8:06
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