Circuitry to Randomize Audio Test Signal

[epsolutions]

I have line level 120Hz sine wave that I want to randomize (not evenly modulate) in amplitude, frequency and/or phase by a factor of about 5-10%. Stated another way, I want to simulate a signal that is slightly unstable in as many ways as are practical, but still essentially a 100Hz "sinusoidal-type" wave form.

What are my options in terms of passive or active circuitry that I can experiment with myself, as opposed to using an arbitrary wave generator, etc?

 

[Harald Kapp]

I see no way to modulate the frequency in a passive way Amplitude and phase can be done by potentiometers and passive filters. But you'll need something/someone to control the passive components making this an aktive circuit again.
The AWG is probably the most suitable solution. At 120 Hz you don't need a fancy brand tool for $$$$. A microcontroller with analog output can easily be used. Do not the pseudo DAC using PWM as e.g. Arduinos do. I recommend one with a true DAC.
An ESPP32 has 8 bit DACs, an STM32 comes with 12 bit resolution much better if you want to modulate the amplitude.

 

[epsolutions]

How about linear mixing with a recorded low frequency sound that is non-repetitive? Maybe something from nature, with low pass filtering to bring it beneath 120Hz. That would modulate the amplitude.

Is there any way this same approach can be used to also modulate phase and /or frequency? I am looking for something more basic than quad multiplication or a programmed chip.

It does not need to be perfect. Just a noticeable effect using "junk box" parts. Because of my location, sourcing components is often an issue.

 

[Harald Kapp]

How about linear mixing with a recorded low frequency sound that is non-repetitive?

That would be additive. but modulating amplitude and/or frequency would be multiplicative.
Linear mixing will preserve the underlying 120 Hz sine.

I'm afraid you'll have to let go of your idea of a purely passive circuit. Some kind of active circuitry will be required.
Amplitude can be modulated by an AM modulator (your favorite search engine will throw dozens of circuits at you).
Frequency modulation will require a more complex FM circuit. Or use an oscillator to generate the 120 Hz sine with variable frequency, e.g. a VCO (Voltage Controlled Oscillator).

Alternatively, use your PC to create the waveform using the PC's audio output.

 

[epsolutions]

Can you recommend an inexpensive multiplier IC for this application that will operate on single supply?

Being very expensive here, I twice I ordered an AD633 from China and they were both fakes. I also looked into a single Gilbert cell. It looked simple, but I suspect getting it to work properly is not, at least for me.

Any further suggestions would be much appreciated.