 5th August 2009, 23:15 #1
 Join Date
 Jul 2009
 Posts
 39
 Helped
 1 / 1
 Points
 834
 Level
 6
energy of sine wave
I confused. Say I have both square wave and sinewave of X Hz.
Now I see both have area unders curve the same.
However, in all experiments I do, I see square wave seem to have more power!
Basics tell me square wave have not only sinewave of X Hz but also odd harmonics of X?
Am I right? Is that why square wave of X Hz seem to have more power than sinewave of X Hz?
 6th August 2009, 09:14 #2
 Join Date
 Jan 2008
 Location
 Bochum, Germany
 Posts
 27,854
 Helped
 8785 / 8785
 Points
 171,707
 Level
 98
energy sine wave
If you actually mean same area under the curve, the sine wave has a higher power.If the square wave has an amplitude of 1, the sine wave must have a peak amplitude of pi/2 for same area. Square wave's power is 1.0 but sine wave's power is 1.11 then.
You don't have to refer to spectral components to calculate the power, simply evaluate the integral of squared amplitude.
 6th August 2009, 09:14
 6th August 2009, 20:13 #3
 Join Date
 Jan 2008
 Location
 Toronto area of Canada
 Posts
 4,611
 Helped
 973 / 973
 Points
 28,419
 Level
 41
square wave power
a squarewave has exactly twice as much power as a sinewave if they both have the same pp voltage.
The harmonics of a squarewave add to produce exactly as much power as the fundamental.
The squarewave is basically a switched DC voltage so its power is V peak squared/R load.
 8th August 2009, 03:05 #4
 Join Date
 Jul 2009
 Posts
 39
 Helped
 1 / 1
 Points
 834
 Level
 6
square sine wave
Audioguru, what you say match with meter output but I still confused. FvM know a lot and he say something other.
What is correct? Wikipedia entry not show anything
 8th August 2009, 11:56 #5
 Join Date
 Jan 2008
 Location
 Bochum, Germany
 Posts
 27,854
 Helped
 8785 / 8785
 Points
 171,707
 Level
 98
sine wave squared
I based my calculation of the square wave fourier series, listed in any profound mathematical handbook. It's (for a squarewave amplitude of h):
For a square wave with an amplitude of 1, the fundamental is 1.27, so it's relative energy share is 81%.Last edited by BlackMamba; 27th August 2010 at 14:15.
1 members found this post helpful.
 8th August 2009, 11:56
 8th August 2009, 14:56 #6
 Join Date
 Jun 2009
 Location
 India
 Posts
 761
 Helped
 145 / 145
 Points
 5,519
 Level
 17
energy in sine wave
A one line solution is to speak in terms of area under the curve of v square plot for comparison of such situations.
This is subject to
1. Constant load.
2. Same frequency of square and sine waves. Else long time integration.

 8th August 2009, 18:02 #7
 Join Date
 Mar 2005
 Location
 USA
 Posts
 1,323
 Helped
 272 / 272
 Points
 11,332
 Level
 25
energy of square wave
tellMeDaBasix,
Consider a sine wave voltage with a peak amplitude of 1V driving a 1 Ohm load. The RMS value of the sine wave is .707V. The power = V^2/R = 0.5W. The average value of the sine wave is 2/pi = .637.
.
Now consider a square wave with the same average value of .637. The RMS and average values of a square wave are the same (.637 in our case). The power dissipated by the 1 Ohm load is V^2/R = (.637^2) = .406W.
.Conclusion: The sine wave has more power.
Regards,
Kral
1 members found this post helpful.
 9th August 2009, 03:04 #8
 Join Date
 Jul 2009
 Posts
 39
 Helped
 1 / 1
 Points
 834
 Level
 6
area of sine wave
OK.. but let me tell you whay I say square have more power.
I connect speaker to electret mic. Mic connected to opmp and then to dso.
1. Now when I feed 5Vpp sine wave I get 2Vpp on DSO.
2. Now when I feed 5Vpp square wave I get 3.2Vpp on DSO.
You see my troubles
 9th August 2009, 03:34 #9
 Join Date
 Jan 2008
 Location
 Toronto area of Canada
 Posts
 4,611
 Helped
 973 / 973
 Points
 28,419
 Level
 41
power of square wave same as power of sine wave
A speaker connected to an electret mic does not do anything without an amplifier.
A speaker cannot be driven by an opamp.
What is a"DSO"?
 9th August 2009, 18:01 #10
 Join Date
 Mar 2005
 Location
 USA
 Posts
 1,323
 Helped
 272 / 272
 Points
 11,332
 Level
 25
energy of sine
TellMeeDaBasix,
In your original post, you were considering a sine wave and a square wave with equal areas (average values). In your last question, you are considering a sine wave and a square wave with equal peak to peak values. In this case, the square wave has a higher RMS value and hence more power will be delivered to the load (speaker).
Regards,
Kral
 9th August 2009, 18:53 #11
 Join Date
 Jul 2009
 Location
 Mumbai
 Posts
 76
 Helped
 12 / 12
 Points
 1,302
 Level
 8
 Blog Entries
 1
square wave squared
DSO is a digital storage oscilloscope.
Like a CRO but has an function to save and modify waveforms/signals. It also has a facility to connect to computer and get pre stored waveforms.
It has 3 modes of operation.
1. Free running mode.
2. Store
3. auto store... or something I dont exactly remember the modes
 9th August 2009, 23:12 #12
 Join Date
 Jan 2008
 Location
 Bochum, Germany
 Posts
 27,854
 Helped
 8785 / 8785
 Points
 171,707
 Level
 98
calculating the energy of a sine wave
Your acoustic signal chain adds an arbitray frequency characteristic to your setup. If you get a higher microphone signal level, this hasn't to do with "power" of the squarewave. Apparently the signal chain is preferring the harmonics to the fundamental.
LinkBacks (?)

Is it a joke to say pair of TDA7293 in parallel can deliver 100+W power into 4ohm  Page 3  diyAudio
Refback This thread2nd June 2013, 17:01