Ramped sine waveform without phase mismatch

[marius246]

Hi there,

I would like to generate a pure tone of 5kHz for 3 seconds with an amplitude that ramps up in the beginning and down at the end of the signal. Does anyone know what the easiest way would be to generate that signal? Is there a way to modulate the amplitude only to avoid phase mismatch between the ramp up signal, the steady sine wave and the ramp down signal?

Thanks for your help!

[mcduff]

Look at these posts. @Bob_Schor has posted a solution earlier.

mcduff

[Bob_Schor]

Yeah, that BS character was pretty clever, but this problem is even easier!  Of course, it's all in the (not-supplied) details ...

• You describe a 5 kHz, 3 second pure tone.  I assume (??) that you mean to produce this as a tone, presumably by coming up with a digital representation of this signal and playing it out through some type of D/A device.  Is this correct?
• If so, how are you planning to generate the appropriate waveform?  Have you thought about the frequency you wish to drive the D/A converter?  [Hint -- it has to be > 5 kHz].
• Once you have your list of numbers, all you have to do is multiply that array by a trapezoidal "amplitude" function, something that starts and ends at 0, plateaus at 1, and rises and falls (linearly) at the speed you want the amplitude to rise and fall.  Do you know how to multiply, point-by-point, two arrays?

Bob Schor

[JÞB]

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@marius246 wrote:

Hi there,

I would like to generate a pure tone of 5kHz for 3 seconds with an amplitude that ramps up in the beginning and down at the end of the signal. Does anyone know what the easiest way would be to generate that signal? Is there a way to modulate the amplitude only to avoid phase mismatch between the ramp up signal, the steady sine wave and the ramp down signal?

Thanks for your help!

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No, there is no way to generate a PURE tone with modulation that has no phase missmatch.  Math just doesn't work that way. 

For whatever it's worth,  I'd LIKE to do that too...

Could you clarify your requirements?