Everything is not equal in a feedback loop

In systems thinking, we often look at a structure known as the feedback loop. There are several variations of the feedback loop. Of these, the reinforcing feedback loop is the one that can you use to improve the most.

This type of feedback loop occurs when the output of a system is fed back into the input. Then it is amplified and sent to the output. The output signal is then fed back into the input of the system to be amplified all over again.

POSITIVE AND NEGATIVE LOOPS

In systems thinking this could be positive or negative. This implies that the loop benefits or degrades us over time.

When someone invests a large percentage of their income this can create a positive feedback loop. They take their extra money and put it somewhere that will grow that money.

Then they take the earnings from the investment and do it all over again. Soon their income is growing from their investments. They can invest even more. The more times they go through this loop the more money they have.

A negative feedback loop is one that continues to diminish. If someone feels stressed and turns to drugs and alcohol to relieve their stress, they can get caught in a negative reinforcing feedback loop.

They feel extra stress and turn to drugs to relieve the stress. But this just masks the stress. Then it goes back into the system and causes additional stress. So, they require more drugs to help relieve the stress. But the drug hides the stress.

Then it gets put back into the input of the system and gets magnified. Over and over. As it does, stress levels increase. The level of drug use necessary to hide stress increases. The person ends up feeling like they are on a downward spiral.

AUDIO FEEDBACK

When people hear about feedback, they often think about the feedback that we hear in a public address (PA) system. This occurs when the output from a speaker goes into the input of a microphone. Then it travels through the audio system, gets amplified, and then pushed out the speakers.

As it does this over and over the microphone squeals. It is a piercing sound. It is very annoying and not something an audio engineer (or the audience) wants to hear in the middle of a show.

For years I worked as an audio engineer and taught audio engineering courses at the local college. Dealing with feedback was a popular topic that we covered in several classes.

One thing about audio feedback is that the signal getting amplified isn’t the full signal. Instead, the squeal that we hear is a small number of frequency bands. So, every system has a tendency to produce a slightly different squeal.

Sometimes the squeal is a low rumble. Sometimes it is at such a high frequency that most people won’t be able to hear it. Sometimes it is 1,000 Hertz. Sometimes it is 800 Hz.

We taught the students that there are several different ways to cut the feedback. We would show them the techniques and then have them practice reducing the feedback.

One way was to use a directional microphone and point it away from the speaker. This helped to shield the microphone from the speaker. In essence, we reduced how much of the signal returned to the input.

But many singers would take the microphone and walk around the stage. The directionality of the microphone helped but still wasn’t enough to control the feedback. As soon as the microphone moved, the feedback would start.

Another adjustment was to turn the volume down. By reducing the volume, we could stop the output from getting put back into the microphone.

But often we needed the volume to be loud enough for the band to hear what they were playing. If we relied on turning the volume down, they wouldn’t hear what they needed, and it would hurt the performance.

So, we taught them a technique to use a graphic equalizer to remove the offending frequencies. This would leave the other frequencies intact. This would mean that we could increase the volume without feedback.

These techniques worked to reduce the feedback loop. We found ways to decrease the amount of output signal returning to the microphone. Or, we found ways to reduce the elements most prone to feeding back.

DECREASING THE STRENGTH OF A NEGATIVE FEEDBACK LOOP

While this was an interesting lesson for audio engineers, we can all learn something important about feedback loops. We can use the same principles to increase or decrease any reinforcing feedback loop.

If we want to reduce a negative feedback loop, we can put more space between the output and the input. If we find that we have a negative feedback loop we can use it to help reduce the impact of the loop.

Let’s say that we have a tendency to overeat when we get stressed. But the more we overeat the more stress comes into our life. We can look at stress reduction techniques. This can reduce the impact from overeating.

Basically, we are reducing the level of the output from overeating. This creates a gap between the output and the input, helping to reduce the impact of the loop.

But we can also use a technique where we focus on certain elements. We might know that certain foods cause us to crave unhealthy food. So, instead of reaching for foods that we know will increase our stress levels, we reach for healthier options. We still might overeat, but the impact becomes less because we focused on the most offending elements and reduced those.

INCREASING THE STRENGTH OF A POSITIVE FEEDBACK LOOP

Or let’s say we want to increase the strength of a positive feedback loop. Maybe we want to exercise to get healthy and feel better about ourselves.

We can decrease the gap between the output (feeling good) and the input (desire to work out). We can do any number of things to magnify how good we feel from the new healthy habits. We can buy clothes that accent our toned muscles. We can compete in 5k races so that we are proud of completing a goal. Doing this will motivate us to keep working out.

Or, we can try to find a few elements that can create the link between output and input. Maybe we find that cardio helps us get our heart rate going and makes it easier to get started. Or, we find that adding strength training helps get quicker results. Whatever it is, we make it more likely that the loop grows, and we benefit.

I learned a lot about audio feedback loops from my time as an audio engineer. But I also learned the same principles apply to many forms of feedback loops.

By learning how to increase or decrease the gap between the output and the input, we can control these loops. Then we can use them to improve our lives.