Ring modulators frequency mix or heterodyne two waveforms, and output the sum and difference of the frequencies present in each waveform. This process of ring modulation produces a signal rich in partials, suitable for producing bell-like or otherwise metallic sounds. As well, neither the carrier nor the incoming signal are prominent in the outputs, and ideally, not at all.
A ring modulator is a tremolo effect, but instead of using an LFO to amplitude modulate audio, an audio signal is used.
But for a “Tremolo” effect the incoming signal is most definitely still prominent - so what should this effect by David Sky be called if it’s not a Ring Modulator?
I don’t know if I can explain one of those without pen and napkin, or waving my hands.
The Ring Modulator was so named because of the ring of (usually) highly matched diodes on a schematic drawing. You don’t even have to know how to read a schematic to find it. “What’s that little ring of parts over there?”
The effect is the same as a doubly-balanced modulator and four-quadrant multiplier. Aren’t you happy?
If you have two audio signals and put them into a ring modulator, the output has some very specific and strange characteristics. Say one signal is rain in the trees “pink noise” and the other is your voice. While you speak, it appears the trees are speaking to us through variation in the rain noise. It’s very disconcerting the first time you hear it.
If either you stop talking or the rain dries up, that’s the end of the output. Neither of the two original signals is present in the output, but the interaction between them is.
Both Color and Colour Television use ring modulators (but not black and white TV) as does Stereo FM (but not Mono FM) and Single Sideband Ham Radio.
No. I don’t know where that came from. I would expect a buzzy square wave playing Chopin. You do need to be careful you don’t get into fantasy land because each of the overtones on both originals generate multiplications, too.
The acid test is see what happens when each signal stops. Single piano notes.
I believe the original engineering was done to try and get sound to go down a very bad phone line.
Thanks Koz - that confirms what I thought.
The second one was created with the “Ring Modulator” plug-in from the Audacity wiki http://wiki.audacityteam.org/wiki/Nyquist_Effect_Plug-ins#Ring_modulator
but it’s not actually a Ring Modulator is it.
The first one is my prototype that was based on the description of a ring modulator in Wikipedia.
This is not an effect that I’m very familiar with so I wanted a second opinion. (thanks).
One other detail that you may be able to help with:
As the RM effect produces sum and difference of the signal and carrier, but both signal and carrier are excluded from the output, I presume that it does not matter which is the signal and which is the carrier?
For example, if Peter Frampton’s magic box has two inputs A and B, he could plug his guitar into A and vocal mic into B or the other way round and get the same effect? (ignoring that one input may be XLR and the other a Jack).
Right. One is the carrier only by convention. As I said, you can get magic results when the two signals are close to each other.
This is electrically what it’s doing.
Note that the phase of the carrier reverses on the negative half of the cycle. Multiply by a negative number.
See: Napkin.
Koz
You can also get magic results (but bad ones) if any of the frequencies get too high. If they do then the Nyquist frequency joins the party and all sorts of extra frequencies start popping out due to the aliasing.
This causes problems when using a square wave carrier (compare the “Plot Spectrum” for a generated “Square Wave” with a generated “Square, no alias”:
I can successfully create nice bandwidth limited square waves that can be used at fairly low frequencies, but I’m running into a problem at higher frequencies (above about 1000 Hz) due to a limit in Audacity Nyquist for the maximum “resolution” (number of samples) allowed for defining a “wavetable” (the lookup table that is used for generating tones). This was the problem with the first sample (ringmod.ogg) - the bandwith is limited too much to give a sense of the squareness of the square carrier, so it’s actually using a short series of sine tones rather than a square wave carrier. I’m still looking for a way round this problem.
Of course.
There’s a brisk trade in tablets at work because for some reason, nobody can draw with a mouse.
There’s a reason square waves are normally associated with sound damage. Square waves, good ones, have infinite harmonics and the modulation produces harmonics and sidebands of the harmonics. Then there’s the Nyquist fold-over thing, so no, I’m not shocked you didn’t get anything useful. Commercial applications of balanced modulation use sine waves and heavy post filtering to get the desired signal and peel off the junk.
Build the square wave wavetable by additive synthesis (so that the square wave is bandwidth limited).
Change the sample rate to a much higher (double) sample rate.
Modulate it with the signal with the carrier.
Brick-wall filter just below the original Nyquist frequency.
Convert back to normal sample rate.
The theory looks good, but I couldn’t work out why I was still getting aliasing unless I brick-walled everything way below the Nyquist frequency (which massively reduces the output bandwidth.
The answer appears to be that [because] Nyquist uses lazy processing, the input signal was not being converted to the higher sample rate. Nyquist could see that the sound was going to be converted back down again, so it didn’t bother converting it up. In turn that meant that the modulation was being processed at the original sample rate and not at the higher rate - hence the aliasing. My current solution (though I’m now looking for a more efficient solution) is to make a copy of the resampled input signal. Using a copy tells Nyquist that “I want it resampled and I want it NOW”. So now I can get alias free ring modulation with an output bandwidth up to almost 19kHz with a 44.1 kHz sample rate.
Build the square wave wavetable by additive synthesis (so that the square wave is bandwidth limited).
Change the sample rate to a much higher (double) sample rate.
Modulate it with the signal with the carrier.
Brick-wall filter just below the original Nyquist frequency.
Convert back to normal sample rate.
The theory looks good, but I couldn’t work out why I was still getting aliasing unless I brick-walled everything way below the Nyquist frequency (which massively reduces the available output bandwidth).
The answer appears to be that [because] Nyquist uses lazy processing, the input signal was not being converted to the higher sample rate. Nyquist could see that the sound was going to be converted back down again, so it didn’t bother converting it up. In turn that meant that the modulation was being processed at the original sample rate and not at the higher rate - hence the aliasing. My current solution (though I’m now looking for a more efficient solution) is to make a copy of the resampled input signal. Using a copy tells Nyquist that “I want it resampled and I want it NOW”. So now I can get alias free ring modulation with an output bandwidth up to almost 19kHz with a 44.1 kHz sample rate.
A Ring Modulator is a damper assembly found on modern church bells. The system is most often used on bells who find themselves in steeples surrounded by congested residential areas. Rather than stop ringing the bells altogether, the Ring Modulator was developed to mute the resonance, sharpness, and volume of each bell as it’s struck, particularly before 8AM/0800hrs, local time, Sunday.
The first pass at design had leather rings placed around the clapper which worked famously, except the wear on the leather was very high and there was no easy control of effect. Later versions had leather or weather resistant vinyl pads in damper arrangement around the outside of the bell housing.
In arrangements where the bell itself moves, the pads travel with the bell and are applied with a control mechanism similar to the pitch control of helicopter blades.
To date there is no computer control over any of the Ring Modulator installations. “That will happen,” one Verger was heard saying quietly, “Over my dead body.”
